Effects of immunological castration (Improvest®) on further processed belly
characteristics and commercial bacon slicing yields of heavy weight finishing pigs
Thesis
Presented in Partial Fulfillment of the Requirements for the Degree of Master of Science in the Graduate School of The Ohio State University
By
Joshua M. Kyle, B.S.
Graduate Program in Animal Sciences
The Ohio State University
2013
Thesis/Master’s Examination Committee:
Dr. Dustin D. Boler, Advisor
Dr. Henry N. Zerby
Dr. C. Lynn Knipe
Copyright by
Joshua M. Kyle
2013
Abstract
The objectives of the first chapter were to summarize the current body of literature pertaining to immunological castration, (Improvest®), and also bacon production in the
United States. The objectives of the second chapter were to conduct an experiment comparing fresh belly characteristics, further processed belly characteristics, and commercial bacon slicing yields of immunologically castrated (IC) barrows, IC barrows fed ractopamine hydrochloride (IC + RAC), physically castrated barrows (PC), intact males, and gilts. One hundred eighty-eight bellies from pigs slaughtered at 130 kg ending live weight were used in the experiment. Fresh bellies were evaluated for flop distance, length, width, and thickness using a ruler. Fatty acid profiles of belly fat were determined on a piece of fat tissue collected along the dorsal edge from anterior end of the belly. Bellies were frozen and transported to the Ohio State University Meat Science
Laboratory after fresh belly characteristic data were collected. Frozen bellies were allowed to thaw, skinned, sorted into treatment groups, and transported to a U.S.D.A federally inspected bacon processing facility for further processing. Bellies were injected with a proprietary brine solution commonly used in bacon production to a target of 113% of green belly weight. Thermally processed bellies were chilled, weighed, pressed, and sliced according to standard plant protocol. Bellies were sliced for a targeted thickness of
24 slices per kg. Complete slices were sorted by trained plant personnel and sliced bellies were transported back to Ohio State. The number of slices and a total sliced belly
ii weight was recorded for each belly. Total PUFA percentage of IC barrows (14.71%) was not different (P = 0.20) from PC barrows (14.17%) or gilts (15.46%), but gilts had a greater (P < 0.05) percentage of total PUFA than PC barrows. Differences in total PUFA proportions were reflected in calculated iodine values. There were no differences (P >
0.05) in calculated iodine value among IC barrows (68.26), PC barrows (67.55) and gilts
(69.45). Commercial slicing yields calculated by green weight of IC barrows (93.61%) were 4.81 percentage units lower (P < 0.01) than PC barrows (98.42%) and 4.58 percentage units lower (P = 0.01) than gilts (98.19%). Commercial slicing yields (green weight) of IC barrows and intact males (93.31%) were not different (P > 0.05).
Ractopamine improved commercial slicing yields (green weight) of IC barrows + RAC by 2.96 percentage units when compared with IC barrows not fed RAC. Commercial slicing yields calculated by cooked weight of IC barrows (90.23%) were 2.66 percentage units lower (P < 0.05) than PC barrows (92.89%) and 2.33 percentage units lower (P <
0.05) than gilts (92.56%). Commercial slicing yields (cooked weight) of IC barrows and intact males (89.09%) were not different (P < 0.05). Ractopamine improved commercial slicing yields (cooked weight) of IC barrows + RAC by 1.12 percentage units when compared with IC barrows not fed RAC. Overall, fresh belly characteristics of IC barrows appear to be more similar to fresh belly characteristics of gilts than to PC barrows, but commercial slicing yields (green and cooked) of bacon manufactured from
IC barrows are less than both PC barrows and gilts.
iii
Dedication
Dedicated to my Father and Mother, James and Crystal Kyle.
iv Acknowledgements
First and foremost I would like to thank my family for their love and support throughout my educational career. This thesis would not have been possible without the unrelenting love and support of my parents and sister. My father has made me strive to work hard every day and develop a work hard, play hard attitude. His wisdom and guidance has always led me down the right path and has allowed me to be successful in my endeavors throughout life. My mother has always been supportive and has always ensured that I have everything I need to be successful. Her high energy, positive attitude, and competitive nature have inspired me to be driven in everything I do. Lastly, I would like to thank my sister, Rachel, for being by my side throughout my educational career.
She has always inspired me to work hard and also to put down the books and have a little fun every now and then.
I owe my deepest gratitude to my advisor Dr. Dustin Boler. Without his guidance, support, and wisdom this thesis would not have been possible. I will always be grateful to him for inspiring me to go to graduate school. I have always admired his passion for meat science, research, teaching, and his students. It was truly an honor to work with him and I will always be grateful that he made my graduate school experience an extremely positive one. He has always pushed me to work hard and encouraged me to be the best in everything I do. I consider it an honor to call him my advisor, mentor, and friend. I would also like to thank my colleagues Ben Bohrer and Kelsey Little. They have
v been by my side through my entire graduate school experience and without their support and friendship I would not be where I am today and therefore I share the credit of my work and success with them. I also would like to thank Dr. Sara Crawford, Alexandra
Gress, Benjamin Wenner, Mike Cressman, and Kyle Culp for welcoming me to The Ohio
State University. They taught me how to be successful in graduate school and made me feel at home in a new city. I will always appreciate and cherish all of the friendships I have made in graduate school.
It is also important for me to thank those that inspired me and supported me during my undergraduate career at the University of Illinois. Dr. Dan Shike taught me how to evaluate livestock and guided me through my undergraduate courses. He inspired me to never give up and encouraged me to attend graduate school in meat science. Dr.
Tom Carr was my coach for the meat animal evaluation team and he taught me how to evaluate carcasses. I will never forget his ability to be a positive influence on those he mentored and his passion for meat science, family, and life. I would also like to thank my professors Dr. Floyd McKeith and Dr. Anna Dilger who have always guided and supported me throughout my academic career.
Finally, I would like to thank the faculty members at The Ohio State University that have influenced me. My two non-advisor members on my masters committee, Dr.
Henry Zerby and Dr. Lynn Knipe, have always pushed me to learn more and have always been there for me when I have asked for their support. I will always admire Dr. Zerby’s
vi enthusiasm for meat science, teaching, and hard work. Dr. Knipe has always supported me in everything I have done and his kindness and processed meats knowledge was always appreciated. I would also like to thank Dr. Steve Moeller for always being supportive; he was always willing to make a trip out to Western Branch to work the pigs.
It is also necessary to thank Ron Cramer, the meat lab manager, for always being helpful during research projects and providing comedic relief while cutting.
vii Vita
May 2007…………………………… Limestone Community High School
May 2011…………………………… B.S. in Animal Sciences, University of Illinois
August 2011 to May 2013……………Graduate Research Associate, Dept. of Animal
Sciences, The Ohio State University
Publications
Bohrer, B.M., Kyle, J.M., Boler, D.D., Rincker, P.J., Ritter, M.J., and Carr, S.N. (2013).
Meta-analysis of the effects of ractopamine hydrochloride on carcass cutability
and primal yields of finishing pigs. J. Anim. Sci. 91: 1015-1023.
Fields of Study
Major Field: Animal Sciences
Area of Interest: Meat Science and Muscle Biology
viii Table of Contents
Abstract……………………………………………………………………………………ii
Dedication……………………………………………………………………………...…iv
Acknowledgments………………………………………………………………………....v
Vita…………………………………...………………………………………………....viii
Table of contents……………………...…………………………………………………..ix
List of Tables…………………………………………………………………………….xii
List of Figures…………………………………………………………………………...xiii
Chapter 1: Review of literature……………………………………………………………1
Introduction………………………………………………………………………..1
Gonadotropin Releasing Factor………………….…………………………….....2
Boar Taint……..…………………………………………………………………..5
Growth Characteristics of Immunologically Castrated Barrows……………….....8
Carcass Characteristics of Immunologically Castrated Barrows………...………13
Estimated Percent Lean of Immunologically Castrated Barrows……...………...17
Carcass Yield (Dressing Percentage) of Immunologically Castrated Pigs…..…..20
Carcass Cutting Yields (Cutability) of Immunologically Castrated Barrows…...24
Pork Quality of Immunologically Castrated Barrows…………………………...28
Sensory Characteristics of Immunologically Castrated Barrows………………..31
Further Processed Characteristics of Immunologically Castrated Barrows……..33
ix Ractopamine Hydrochloride and Immunological Castration…………………....37
Bacon Production in the United States…………………………………………..41
History…………….………………………………………………..41
Manufacturing Pork Bellies Into Bacon…….……………………...42
Methods of Curing………………………………………………….42
Common Additives…………………………………………………43
Salt (Sodium Chloride: NaCl)………………………………………44
Sweeteners……………………………..…...………………………45
Nitrate/Nitrite……………………………...………………………..45
Phosphates…………………………………………………………..46
Cure Accelerators……………………..…………………………....46
Water…………………………………..……………………………47
Cured Meat Color/Reaction…………..…………………………….47
Bacon Quality………………………...……………………………..48
Literature Cited…………………………………………………………………..51
Chapter 2: Effects of immunological castration (Improvest®) on further processed belly characteristics and commercial bacon slicing yields of heavy weight finishing pigs………………………………………………….……………………………………58
Abstract…………………………………………………………………………..58
Introduction………………………………………………………………………60
x Materials and Methods…………………………………………………………...61
Results and Discussion…………………………………………………………..68
Fresh Belly Characteristics………………………………………………………68
Fatty Acid Profile…....…………………………………………………………...69
Cured Belly Characteristics.……………...………………………………………71
Number of Slices and Slicing Yields……….…………………………………….72
Variability of Bacon Slicing Yields…..…………………………………………..73
Pearson Correlation Coefficients of Commercial Bacon Slicing Yields…………75
Bacon Composition……………………………………………………………….76
Bacon Slice Lean:Fat Image Analysis……...…….………………………………76
Conclusions……………...………………..………………………………………79
Literature Cited………...………………………………………………………….81
Complete Literature Cited……………………….…………………………………92
xi List of Tables
Table 1. The effects of immunological castration on fresh belly characteristics of heavy weight finishing pigs……………………………………………………………………..84
Table 2. The effects of immunological castration on fatty acid profiles of heavy weight finishing pigs……………………………………………………………………………..85
Table 3. The effects of immunological castration on processing characteristics of heavy weight finishing pigs……………………………………………………………………..86
Table 4. Pearson correlation coefficients (r) of commercial slicing yields (green weight) and bacon processing characteristics………………………….………………….……..87
Table 5. Pearson correlation coefficients (r) of commercial slicing yields (cooked weight) and bacon processing characteristics…………………………………………………….88
Table 6. The effects of immunological castration on bacon slice lean to fat ratios of heavy weight finishing pigs…………………………….………………………………..89
xii List of Figures
Figure 1. Variation of commercial bacon slicing yields of immunologically castrated (IC) barrows, physically castrated (PC) barrows, intact males, and gilts when expressed as a proportion of green weight using the mathematical equation: slicing yield (green weight)
= (sliced weight / green weight) * 100.……….…….…………………………...……....90
Figure 2. Variation of commercial bacon slicing yields of immunologically castrated (IC) barrows, physically castrated (PC) barrows, intact males, and gilts when expressed as a proportion of cooked weight using the mathematical equation: slicing yield (cooked weight) = (sliced weight / cooked weight) * 100…………………..………………….…91
xiii Chapter 1: Review of Literature
Introduction
Immunologically castrated barrows grow faster post second injection (Dunshea et al., 2001; Fàbrega et al., 2010) have leaner carcasses (Jaros et al., 2005; Schmoll et al,
2009; Fuchs et al., 2009) and greater carcass cutability (Gispert et al., 2010; Morales et al., 2010; Boler et al., 2011a, 2012) than physically castrated barrows. Feed efficiency in
IC barrows is on average 8.41 percent better than PC barrows. Average daily gain is increased on average by 4.28 percent when compared to PC barrows (Dunshea et al.,
2013). Cutting yields are improved by 2 to 2.5 percentage units on average when compared to PC barrows (Boler et al., 2011a). Additionally, fresh meat quality characteristics such as drip loss (Pauly et al., 2009; Boler et al., 2012), cook loss (Pauly et al., 2009; Boler et al, 2011a), ultimate pH (D’Souza and Mullan, 2003; Pauly et al., 2009;
Gispert et al., 2010), and lean color (Pauly et al., 2009; Boler et al., 2011a, 2012) are not different (P > 0.05) between IC and physically castrated barrows. Immunologically castrated barrows have a greater proportion of the loin, shoulder and ham, but tend to have thinner bellies and narrower flop distances than physically castrated barrows (Boler et al., 2011b, 2012). Furthermore, when distiller’s grains were added to the diet, IC barrows had a greater concentration of PUFA, which resulted in a higher calculated iodine value (Zoetis Internal Report-Tavárez et al., 2013) than physically castrated barrows. Thinner bellies (Person et al., 2005) and greater PUFA concentrations
1 (Shackelford et al., 1990) caused a reduction in bacon slicing yields. Even though bacon processing characteristics were not different among sexes (Boler et al., 2011b, 2012), there are no data currently available for the effect of immunological castration on commercial bacon slicing yields. Therefore, the objectives of this thesis were to compare fresh belly characteristics, further processed belly characteristics, and commercial bacon slicing yields among IC barrows (IC), IC barrows fed ractopamine hydrochloride (IC +
RAC), physically castrated barrows (PC), intact males (IM), and gilts (G).
Gonadotropin Releasing Factor
The product, Improvest (Zoetis, Kalamazoo, MI), is defined as a gonadotropin releasing factor analog – diphtheria toxoid conjugate. Gonadotropin releasing hormone, or GnRH is a hormone produced by all mammals and can also be referred to as
Gonadotropin releasing factor, or GnRF. Zoetis has chosen to market their product under the GnRF synonym in order to avoid the negative connotations associated with hormones. Gonadotropin releasing factor analog, or GnRF is a compound that all mammals produce naturally as they mature. Improvest does not contain the naturally occurring GnRF. Rather, it contains an incomplete version of the naturally occurring hormone, an analog, which makes it orally inactive. Diphtheria toxoid (DT) is the same as the standard diphtheria vaccine that has been safely used in global childhood vaccination programs since the 1930s (Atkinson et al., 2009) It is simply a protein that contains natural amino acids, it is used as the carrier (conjugate) protein for the incomplete GnRF molecule. Conjugate means "to join together." The two compounds need each other to produce the immunological response in the pig.
2 Gonadotropin releasing factor is a neuropeptide that is released in a pulsatile manner. It is a sex hormone in both males and gilts that is responsible for the release of follicle stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary.
Gonadotropin releasing factor is synthesized and released from neurons within the hypothalamus. GnRF is considered a neurohormone, a hormone produced in a specific neural cell and released at its neural terminal axis. A key area for production of GnRF is the preoptic area of the hypothalamus, which contains most of the GnRF-secreting neurons (Campbell et al., 2009). Gonadotropin releasing factor neurons originate in the nose and migrate into the brain, where they are scattered throughout the medial septum and hypothalamus and connected by >1-millimeter-long dendrites. These bundle together so they receive shared synaptic input, a process that allows them to synchronize their GnRF release (Campbell et al., 2009).
Gonadotropin releasing factor is secreted into the hypophysial portal bloodstream at the median eminence (Campbell et al., 2009). The portal bloodstream system then carries the GnRF to the anterior pituitary gland, which contains the gonadotropic cells, where GnRF activates its own receptor, gonadotropin-releasing factor receptor (GnRFR), a seven-transmembrane G-protein-coupled receptor that stimulates the beta isoform of phosphoinositide phospholipase C, which goes on to mobilize calcium and protein kinase
C (Campbell et al, 2009). This results in the activation of proteins involved in the synthesis and secretion of the gonadotropins LH and FSH. Gonadotropin releasing factor is degraded by proteolysis within a few minutes, creating a pulsatile response instead of a continuous one.
3 Once GnRF has reached the anterior pituitary, it stimulates the synthesis and secretion of the gonadotropins; follicle-stimulating hormone (FSH), and luteinizing hormone (LH). These secretion processes are dictated by the size and frequency of
GnRF pulses, as well as by feedback from androgens and estrogens. Low-frequency
GnRF pulses lead to FSH release, whereas high-frequency GnRF pulses stimulate LH release. There are differences in GnRF secretion between females and males. In males,
GnRF is secreted in pulses at a constant frequency, but, in females, the frequency of the pulses varies during the menstrual cycle, and there is a large surge of GnRF just before ovulation. GnRF secretion is pulsatile in all vertebrates, and is necessary for correct reproductive function. Thus, this single hormone, GnRF, controls a complex process of follicular growth, ovulation, and corpus luteum maintenance in the female, and spermatogenesis in the male (Davidson and Stabendeldt, 1997).
In the male, regulation of the synthesis of testosterone is controlled by LH and
FSH. This is achieved primarily by the regulation of LH traveling from the anterior pituitary to the testes. Once in the testes, LH binds to membrane receptors on the leydig cells of the testes and causes a conversion of cholesterol to testosterone (Davidson and
Stabendeldt, 1997). Testosterone and FSH act upon receptors in sertoli cells of the seminiferous tubules which activates synthesis of androgen-binding protein. Sertoli cells and leydig cells communicate via paracrine signaling completing a positive feedback loop of the two hormones. Immunologically blocking the signal from GnRF will lead to decreased production of LH, FSH, and testicular steroids (Zamaratskaia et al., 2008).
This will lead to decreased levels of testosterone, allowing increased hepatic metabolism
4 of the negative compounds associated with meat derived from intact male pigs. These compounds are generally referred to as boar taint.
The production protocol for raising immunologically castrated pigs can be divided into two phases from a physiological perspective (Dunshea et al., 2013). Since the product works through immunization, two doses are required at a minimum interval of four weeks apart. The first dose is the priming dose, allowing the body to create antibodies that act upon GnRF, this dose is generally given any time after 10 weeks of age, or after puberty in the pig. The second dose is typically given four to six weeks prior to slaughter and until shortly after the second dose the pig is physiologically an intact male. Following the second dose, testicular function is suppressed and hormonal status quickly changes to resemble that of a physically castrated barrow (Dunshea et al., 2001).
The second dose is when antibodies become activated against GnRF, causing a suppression of its release from the hypothalamus, which leads to the suppression of the pulsatile release of LH and FSH from the anterior pituitary and furthermore testosterone from the gonads. By disrupting the hypothalamic-pituitary-gonadal axis, this process produces the same effect as physical castration.
Boar Taint
Boar taint has been characterized as the accumulation of certain chemical agents in adipose tissue of mature, intact males pigs and some physically castrated barrows and gilts (Bonneau, 1982). Two chemicals: 5α-androstenone (5α -androst-16-ene-3-one) and skatole (3-methyl indole) are the compounds most frequently associated with boar taint
(Patterson, 1968; Bonneau, et al, 2000). 5α -androstenone is a testicular steroid and is associated with a distinct urinary odor. Skatole is a product of bacterial degradation of
5 the amino acid tryptophan in the hind gut and has been associated with a strong fecal odor (Bonneau, 1998). Therefore, skatole can also be influenced by diet (Andersson et al., 1997; Zamaratskaia., 2005) or environment (Zamaratskaia et al., 2008) and causes issues with boar taint in barrows, gilts, and intact males. Environmental influences are usually associated with management, including stocking density, cleanliness of pens, slatted or solid floors, and ventilation. All of these factors have been proved to influence the levels of skatole in all pigs, regardless of sex (Zamaratskaia et al., 2008). Sex steroids, such as testosterone and androstenone inhibit hepatic metabolism of skatole which allow it to accumulate in fat tissue of both male and female pigs (Babol et al.,
1999).
The accumulation of these boar taint compounds leads to offensive odors and off- flavors in the meat and will lead to dissatisfaction with the experience of eating pork. It is generally considered an issue with intact males, but is not gender exclusive. Boar taint can be detected in barrows and gilts, particularly in cases where pigs are housed in conditions of poor environmental hygiene. Historically, sexually mature intact males have not been used in finishing production systems because of their tendency to cause objectionable odors and undesirable flavors in the meat (Babol and Squires, 1995). Boar taint is commonly controlled in the United States and other countries by physical castration. Since androstenone is a testicular steroid the most efficient way to eliminate this substance is physical castration. Furthermore, studies have shown that castration also reduces skatole levels (Font i Furnols et al., 2008). Other countries such as the United
Kingdom, Ireland, and Australia who sometimes do not castrate male pigs often slaughter prior to sexual maturity, at a lighter finished weight than the United States in order to
6 avoid boar taint issues. Immunological castration has proved to be an effective tool rather than physical castration to eliminate boar taint by reducing adrostenone and skatole levels (Dunshea et al., 2001; Zamaratskaia et al., 2008; Font i Furnols et al., 2009).
Concentrations between 0.50 μg/g and 1.00 μg/g for 5 α-androstenone and between 0.20
μg/g and 0.25 μg/g for skatole are generally accepted as thresholds for quantitatively distinguishing differences between tainted and untainted pork samples (Godt, et al, 1996;
Bonneau, 1998). There are no standard thresholds for assessment of taint or standard methods for trained sensory or consumer panels to score samples as tainted or not (Prusa et al., 2011).
The relative contributions of 5 α-androstenone and skatole to boar taint have been investigated in multiple studies. Coefficients of correlation between fat 5 α– androstenone or skatole levels and boar taint intensity, assessed by trained laboratory panels, range between 0.4 and 0.8 (Bonneau, 1993), suggesting that both of these compounds make significant contributions to boar taint. The lack of consistency among the results obtained in various studies is understandable and may be attributed to differences in the 5 α-androstenone and skatole characteristics of the animal populations from which samples were drawn. Differences in the methodology used for sensory assessment of odors (Bonneau, 1993; Dijksterhuis, et al 2000) could also account for some of the variation, including selection and training of panel members, cultural influences, preparation, and presentation of the samples (Prusa et al., 2011).
A study by Prusa et al., (2011) was conducted to evaluate the prevalence of boar taint in the United States. A trained panel evaluated aroma and analytical detection of boar taint compounds (5 α-androstenone and skatole) in commercially available fresh
7 pork loins, without knowledge of herds orgin or herd management conditions.
Concentrations of 5 α-androstenone (liquid chromatography/mass spectroscopy) and skatole (liquid chromatography with fluorescent detection) in backfat were measured for the analytical detection of boar taint compounds. A trained panel evaluated boar taint aroma in heated samples. Samples were heated in a conventional microwave oven for 15 to 20 seconds on high power. After the initial heating, samples were rotated front to back and heated for an additional 20 seconds for fat tissue and 15 seconds for lean tissue.
Mean 5 α-androstenone and skatole levels were low among PC barrows, gilts, and sows, however, 55.8% of intact males scored above a 1.0 μg/g threshold for 5 α-androstenone concentrations and 34.2% were above a 0.2 μg /g threshold for skatole concentrations.
Mean aroma scores for backfat and lean from PC barrows, gilts, and sows were low.
Lean aroma sores that were greater than 50mm were 7.2 % of the PC barrows, 2.8 % of the gilts, and 9.2 % of the sows. Backfat aroma scores were also low, 3.3 % of the PC barrows, 1.1 % of the gilts, and 5.0 % of the sows had aroma scores greater than 50mm.
In comparison, 59.2% of intact males had elevated mean aroma scores from fat samples and 31.7% from lean. Importantly, boar taint aroma was detectable by the trained panel in at least some animals in each of the sex classes (Prusa et al., 2011).
Growth Characteristics of Immunologically Castrated Barrows
Raising boars for pork production has significant economic advantages over castrates. Boars have greater feed efficiency, grow faster, and produce leaner carcasses than barrows or gilts (Babol and Squires, 1995; Bonneau, 1998; Dunshea et al., 2001,
2011). However, these advantages come with the risk of boar taint, which is why physical castration (PC) is a common practice that is utilized in the swine industry. In
8 recent years, animal welfare activists are lobbying for a cessation of physical castration in many parts of the world, particularly the EU, with a high likelihood that this could lead to inferior pork and processed products, alternative technologies are being considered that can be affective while still maintaining pork quality (Dunshea et al., 2010). An alternative to physical castration is immunological castration (IC), which allows producers to capitalize on the natural growth and carcass characteristics of intact boars without the risk of boar taint. Immunological castration results in superior feed efficiency and carcass lean yield over physical castration, while maintaining pork eating quality (Dunshea et al., 2013).
Improvements in growth and efficiency of IC barrows have been well documented in several peer reviewed articles when compared to PC barrows. Dunshea et al. (2001) reported that IC barrows had a 10% improvement in growth over intact males and a 7% improvement in growth over PC barrows during the last 4 weeks of feeding prior to harvest. Furthermore, ADG of IC barrows was improved 30% compared to intact males and improved 32% compared to PC barrows. Also, in a follow up study, Dunshea et al. (2011) concluded that ADG of IC barrows was improved 20% compared to intact males and improved 15% compared to PC barrows. Importantly, the variation in body weight of IC barrows was also less, which is not only economically important, but makes management of nutrition and sales easier. Dunshea et al. (2001) found that feed intake for
IC barrows were 15% higher (P=0.006) than intact males, but feed conversion ratios (g/g) were very similar. Intact males had conversion ratios (F:G) at 3.03 and IC barrows were at 3.05. Similar results were reported in the follow up study by Dunshea et al. (2011),
9 entire males and IC barrows had the same G:F (0.36), but this was 10% greater than the
PC barrows (0.33).
Furthermore, a study by Fabrega et al. in 2010 reported similar results. Until the second injection, ADG was greatest (P < 0.05) in PC barrows (928.16 g/d). After the second injection, ADG was greatest (P < 0.05) in IC barrows (1160.04 g/d), however over the entire study period, there was no significant difference in ADG between PC
(898.32 g/d) and IC barrows (936.55 g/d). Also, until the time of the second injection, feed consumption of PC barrows (2136.72 g/d) was significantly greater (P < 0.05) than in the other three treatment groups (intact males, IC barrows, and gilts). However, after the second injection feed consumption was significantly greater (P < 0.05) in IC barrows
(3446.65 g/d) than the other three treatment groups (intact males, gilts, and PC barrows).
The overall feed consumption of PC (2482.61 g/d) and IC barrows (2355.57 g/d) throughout the entire study period did not differ significantly (P > 0.05). Feed
Conversion ratios (F:G) were significantly less (P < 0.05) in IC barrows from the beginning of the finishing period until the second injection, from the second injection to slaughter, and during the finishing period as a whole when compared to PC barrows and gilts. Over the entire finishing period, feed conversion ratio of IC barrows were 9% lower than PC barrows and 4% lower than gilts.
Contrary to Dunshea et al. (2001, 2011) and Fabrega et al. (2010), Zamaratskaia et al. (2008) reported no differences (P > 0.05) in ADG of intact male pigs, IC barrows, or PC barrows during the growing phase before the second injection. However,
Zamaratskaia reported results similar to the other studies in terms of ADG after the 2nd injection. Immunologically castrated barrows grew 150 g/d more than intact males (1257
10 g/d for IC vs. 1107 g/d for intact males) and 170 g/d more than PC barrows (1257 g/d for
IC vs. 1090 g/d for PC barrows). Feed conversion ratios (F:G) were also similar for IC males (3.05 kg/kg), physically castrated males (3.20 kg/kg) and intact males (2.90 kg/kg)
(P = 0.14). Feed intake in this study was not different (P = 0.13) among the three treatment groups, IC barrow at 294 kg, PC barrow at 318 kg, Intact male at 280 kg
(Zamaratskaia et al., 2008).
Font i Furnols et al., (2012) reported similar results. There were no significant differences (P > 0.05) in live weight between sexes (gilts, intact males, PC and IC barrows) at the time of first injection (V1) and second injection (V2) by using immunological castration. However, at the end of the treatment, IC barrows were 5.8 kg heavier than PC barrows (P = 0.0004) and 6.1 kg heavier than gilts (P = 0.0003). This can be explained because ADG of IC barrows from V1 to slaughter (S-1) and especially from V2 to S-1 was greater than gilts and PC barrows. In other studies a lack of difference in the ADG from V1 to S-1 between PC barrows and IC barrows during this period was reported (Fàbrega et al., 2010; Jaros et al., 2005; Morales et al., 2010; Škrlep et al., 2010). A possible explanation for these studies seeing a lack of differences in sexes in terms of ADG is that these studies administered the second injection between
140 d and 154 d and pigs were slaughtered between 100 kg and 120 kg live weight, whereas in this study pigs were injected secondly at 172 d of age and slaughtered heavier, at 138 kg live weight and at 215 days of age.
Font i Furnols et al., (2012) also reported an increase in ADG after the second vaccination in IC barrows similar to (Dunshea 2001, 2011; Fabrega 2010; Pauly 2009;
Zamaratskaia 2008; Morales 2011). Average daily gain from V2 to S-1 was 139.3 g/day
11 greater (P = 0.0004) in IC barrows than in PC barrows and 145.9 g/day higher (P =
0.0003) than in gilts.
Ellis et al (2013) researched the effects of immunological castration of males with an anti-GnRF immunological product (Improvest®) in comparison with PC barrows, gilts, and intact males on pig growth performance when fed RAC. Overall results of this study concluded that the ADG of IC barrows fed ractopamine (1195 g/d) was the greatest, but was not significantly different (P > 0.05) from IC barrows not fed RAC (1150 g/d).
However, IC barrows overall ADG (1150 g/d) was significantly greater than intact males
(1064 g/d), PC barrows (1024 g/d) and gilts (954 g/d). Average daily feed intake was numerically the greatest in IC barrows (3.11 kg/d), however was not significantly different (P > 0.05) from PC barrows (3.06 kg/d) or IC barrows fed RAC (3.04 kg/d).
Even though IC barrows (3.11 kg/d) had the greatest feed intake, they were still more efficient (P < 0.05) in their gain:feed than PC barrows (0.335). Intact males (0.397) and
IC barrows fed RAC (0.394) had the greatest gain:feed ratio, and were followed closely by the IC barrows (0.371). Immunologically castrated barrows (0.371) were more efficient (P < 0.05) throughout the finishing period than gilts (0.347) and PC barrows
(0.335).
When viewing the published literature regarding the differences in growth characteristics between PC barrows and IC barrows, several conclusions have been established. Physically castrated barrows have a greater (P < 0.05) ADG prior to second injection than PC barrows (Fabrega et al., 2010) However, after the second injection, average daily gain is greater in (P < 0.05) in IC barrows than PC barrows (Dunshea et al.,
2001, 2011; Fabrega et al., 2010; Zamaratskaia et al., 2008; Font i Furnols et al., 2012).
12 The increase in ADG post second injection results in a greater overall ADG in the IC barrows throughout the entire finishing period (Ellis et al., 2013). Until the time of the second injection, feed consumption of PC barrows is greater than IC barrows (Fabrega et al., 2010). However, after the second injection feed consumption is significantly greater
(P < 0.05) in IC barrows than PC barrows (Dunshea et al., 2001, 2011; Fabrega et al.,
2010). Feed consumption throughout the entire feeding period between PC barrows and
IC barrows does not differ (P > 0.05) (Fabrega et al., 2010; Zamaratskaia et al 2008; Ellis et al., 2013). Feed Conversion ratios (F:G) are significantly lower (P < 0.05) in the IC group from the beginning of the finishing period until the second injection, from the second injection to slaughter, and during the finishing period as a whole when compared to PC barrows (Fabrega et al., 2010; Dunshea et al., 2001, 2011; Ellis et al., 2013). A consensus of recently published works shows that over the entire finishing period, IC barrows have a 4.28% increase in ADG and an 8.41% increase in feed efficiency when compared to PC barrows (Dunshea et al., 2013).
Carcass Characteristics of Immunologically Castrated Barrows
Dunshea et al., (2013) conducted a meta-analysis of recently published literature, to be specific 11 studies since the year 2000 were used to compare carcass characteristic between IC and PC barrows. Final slaughter measurements were taken, reflecting growth both before and post second injection. Immunologically castrated barrows had an increased ending live weight (+ 2.2 kg, P < 0.05), decreased P2 back fat thickness (- 2.6 mm, P < 0.05) and decreased dressing percentage (- 1.6 points, P < 0.05), with no effect on carcass weight (+ 0.45 kg, P = 0.41) compared to PC barrows (Dunshea et al., 2013).
Several peer reviewed publications have shown multiple differences in carcass
13 characteristics between IC and PC barrows. The majority of the publications have demonstrated economic advantages in raising IC managed barrows in terms of carcass characteristics over PC barrows.
Pauly et al., (2009) evaluated the growth performance, carcass characteristics and meat quality of group-penned PC barrows, IC barrows and intact males. Hot carcass weights were not significantly different (P > 0.05) between the treatment groups, PC barrows (85.0 kg), IC barrows (83.9 kg), and intact males (84.0 kg). However significant differences were observed in 10th rib backfat thickness (mm). As anticipated, intact males (17.8 mm) had the least (P < 0.05) 10th rib backfat thickness. Immunologically castrated barrows (19.3 mm) were intermediate and PC barrows (24.9 mm) had the greatest (P < 0.05) 10th rib backfat thickness (Pauly et al., 2009).
Fabrega et al., (2010) looked at the effect of immunological castration on growth performance, body composition, and found similar results in backfat thickness and loin depth. As anticipated, at the time of slaughter, intact males (10.17 mm) had the least backfat thickness but were not significantly different (P > 0.05) than the gilts (11.45 mm). Physically castrated barrows (14.99 mm) numerically had the most backfat thickness, however they were not different (P > 0.05) than the IC barrows (13.17 mm).
Furthermore, at the time of slaughter there were no significant differences between treatment groups in terms of loin depth. Very similar loin depths were observed across treatment groups; PC barrows (60.19 mm), IC barrows (59.50 mm), intact males (58.41 mm), and gilts (59.42 mm) (Fabrega et al., 2010).
Boler et al., (2011a) determined the effects of different lysine supplementation on
IC barrows compared to PC barrows and found similar results, ending live weights of IC
14 barrows fed the medium/high lysine diet and low/medium lysine diet were greater (P <
0.05) than PC barrows. Furthermore, hot carcass weights (HCW) for IC barrows fed medium/high lysine diets were heavier (P < 0.05) than PC barrows, IC barrows fed low or high lysine diets, and intact males. However in a follow up study, Boler et al., (2013) found no differences (P > 0.05) in HCW among IC barrows (102.9 kg), PC barrows
(103.4 kg), intact males (101.6 kg), and gilts (101.9 kg), but IC barrows were not fed the optimum level of lysine in this experiment. Dressing percent was less (P < 0.05) for IC barrows and intact males compared to PC barrows (Boler et al., 2011a).
Immunologically castrated barrows fed the high lysine diet had a deeper loin depth (P <
0.05) than intact males. No other differences (P > 0.05) were detected among other treatment groups for loin depth. Furthermore, no differences were detected for fat depth among PC barrows, IC barrows fed low lysine, IC barrows fed low/medium lysine, or IC barrows fed medium/high lysine. Intact males had less fat depth (P < 0.05) when compared with the other treatment groups with the only exception being IC males fed high lysine (P > 0.05). This study demonstrated that as dietary lysine inclusion is increased in the diet, backfat tended to decrease in IC barrows. Also, loin eye areas of
PC barrows were smaller (P < 0.05) than LEA of IC barrows fed medium/high lysine, IC males fed high lysine, and intact males (Boler et al., 2011a).
Boler et al., (2012) evaluated the effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of IC barrows and found similar differences in carcass characteristics when compared to PC barrows. Ending live weights, averaged over both slaughter times post-second injection, of the IC barrows were 5.5 kg heavier (P < 0.01) than PC barrows. Although there was an advantage in
15 ending live weight of IC barrows over PC barrows hot carcass weights were not different
(P > 0.05), this can be attributed to the decrease in dressing percentage of IC barrows compared to PC barrows. Hot carcass weights of PC barrows (91.98 kg) were not significantly different (P > 0.05) than IC barrows (92.52 kg). Furthermore, no differences were discovered (P > 0.05) in loin depths between IC barrows (61.0 mm) and
PC barrows (62.8 mm), but IC barrows possessed less (P < 0.05) 10th-rib backfat than
PC barrows.
Boler et al (2013) found similar results in terms of differences in hot carcass weights, loin eye areas and backfat thickness between IC barrows, IC barrows fed RAC,
PC barrows, intact males, and gilts. Immunologically castrated barrows fed RAC had the heaviest hot carcass weights (106.3 kg). There were no differences in HCW among IC barrows (102.9 kg), PC barrows (103.4 kg), intact males (101.6 kg), and gilts (101.9 kg).
It is important to note that in this experiment pigs were fed to a common ending live weight of about 130 kg, which explains the heavy hot carcass weights. Furthermore, IC barrows fed RAC had larger (P < 0.05) loin eye areas than IC barrows not fed RAC, PC barrows, and intact males. There were no differences (P > 0.05) in loin eye area between
IC barrows fed RAC and gilts, also gilts were not significantly different (P > 0.05) from the other three treatment groups. As anticipated, intact males (1.82 cm) had the least (P <
0.05) 10th rib backfat among all the treatment groups. Also, as anticipated, PC barrows
(2.52 cm) had the most backfat, but they were not significantly different (P > 0.05) from the IC barrows (2.43 cm). Immunologically castrated barrows fed RAC (2.21 cm) were intermediate in their backfat thickness and were not different (P > 0.05) from the gilts
(2.11 cm)
16 Based on the meta-analysis conducted by Dunshea et al., (2013) several conclusions can be made about the carcass characteristics of IC barrows compared to PC barrows. When evaluating multiple studies the results demonstrated that IC barrows had an increased ending live weight (+ 2.2 kg, P < 0.05), decreased P2 back fat thickness (-
2.6 mm, P < 0.05) and decreased dressing percentage (- 1.6 points, P < 0.05), with no effect on carcass weight (+ 0.45 kg, P = 0.41) compared to PC barrows (Dunshea et al.,
2013). Several peer reviewed publications have shown multiple differences in carcass characteristics between IC and PC barrows. The majority of the publications have demonstrated economic advantages in raising IC managed barrows in terms of carcass characteristics over PC barrows.
Estimated Percent Lean of Immunologically Castrated Barrows
Several peer reviewed research publications have confirmed that estimated percent lean meat is greater in IC barrows when compared to PC barrows (Jaros et al.,
2005; Zamaratskaia et al., 2008; Fuchs et al., 2009; Pauly et al., 2009; Gispert et al.,
2010; Boler 2011b, 2012). It is logical to infer that IC barrows will have a higher estimated percent lean when compared to PC barrows because IC barrows resemble intact males in terms of their growth and efficiency for a large portion of their life. Andersson et al. (1997) reported that intact males, 64.2% lean meat, had a 4 percentage unit advantage in lean meat content by means of partial dissection when compared to PC barrows, at 60.1% lean meat content. This increase in lean meat content of IC barrows compared to PC barrows is usually coupled with a reduction in back fat. There are a variety of tools available to determine estimated lean meat. Some include the Fat-O-
Meater (Gispert et al., 2010; Boler et al., 2011a,2012), ultrameter (Jaros et al., 2005), the
17 Hennessy probe (Fuchs et al., 2009; Rikard-Bell et al., 2009), and dual energy x-ray absorptiometry (Oliver et al., 2003; Moore et al., 2009; Rikard- Bell et al., 2009).
Jaros et al., (2005) reported greater (P < 0.001) percent lean estimates of IC barrows when compared to PC barrows when using an ultrameter. At harvest, pigs were ultrasounded to determine percent lean estimates. Estimated percent lean was expressed as lean meat as a percentage of the total carcass weight. Immunologically castrated barrows had an estimated percent lean value between 54.3% and 54.7%. Confidence intervals for PC barrows were between 53.5% and 54.0%. Average estimated percent lean was 54.5% for IC barrows and 53.8% for PC barrows (Jaros et al., 2005).
Fuchs et al. (2009) used 554 terminal crossbred barrows separated by castration method, PC barrows (n = 274) and IC barrows (n = 280). Estimated percent lean meat was determined in this study using a Hennesy Probe. Estimated lean meat percentage was 1 percentage unit greater (P < 0.0001) in IC barrows (54.8%) when compared to PC barrows (53.8%). Carcasses were categorized based on percent lean meat estimation using EUROP standards: > 55% lean meat graded E, 50% - 54.9% graded U, 45% -
49.9% graded R. Ninety six percent of all IC barrows graded at least 50% lean meat
(Grade E or U) and 49% graded E, compared to 91% of the PC barrows grading E or U with 36% grading E. Even though this study found a significant difference in estimated percent lean meat between PC and IC barrows, it is important to indicate that this method for determining lean meat percentage is underestimating the percentage of lean meat.
This is apparent when viewing the results of Andersson et al., (1997), where lean meat percentage was determined by means of partial dissection.
18 Zamaratskaia et al. (2008) reported similar advantages in estimated percent lean.
Immunologically castrated barrows had a 1.2 percentage unit advantage in lean meat content (56.1%) over PC barrows (54.9%) when percent lean was estimated with a
Hennessy probe. These estimates were however, not statistically different (P > 0.05). As expected, both PC and IC barrows had lower (P < 0.05) estimated percent lean values when compared to intact males (57.8%). Boler et al., (2011a) determined the effects of different lysine supplementation on IC barrows compared to PC barrows and found similar results. Immunologically castrated barrows have a greater estimated percent lean meat content, range 55.8 to 57.5 %, using a Fat-O-Meater, than PC barrows (55.2 %), but a decreased estimated lean than intact males (58.0 %) even though the magnitude of the difference did not reach statistical significance. However, the IC barrows fed high lysine
(57.5 %) had a greater (P < 0.05) lean meat estimate than PC barrows (55.2 %). In a follow up study, Boler et al., (2012) also found a lack of statistical differences (P = 0.09) between IC (56.25%) and PC barrows (55.65%) in terms of estimated carcass lean, even though there was a numerical advantage in the IC barrows.
Zamaratskaia et al., (2008) followed up on the Hennessy probe estimates for percent lean by conducting a partial carcass dissection to get another parameter estimate for percent lean meat content. The ham from the right side of each carcass was initially weighted and skinned, trimmed to a standardized fat level, and reweighed to calculate a lean meat percentage estimate. With this set of values an estimate of percent lean was statistically different (P < 0.05) between the IC (58.5%) and the PC barrows (56.5%).
Both groups still had lower (P < 0.05) percent lean estimates than intact males (60.2%), however this was anticipated. Boler et al., (2011a) also followed up the Fat-O-Meater
19 estimation, right sides of each carcass were dissected into skin, bone, and soft tissue, determining a more accurate fat-free lean value. Fat-free lean was less (P < 0.05) for PC barrows (53.8 %) when compared with intact males (64.2 %) or any of the IC barrows dietary treatment groups, regardless of Lysine inclusion in the diet, (range of 56.1 to 59.8
%). Intact males, as anticipated, had the greatest (P < 0.05) fat-free lean of any other treatment groups. As lysine levels increased in IC barrows, there was also a linear increase in fat-free lean. In both of these studies, the methods for estimating fat-free lean are failing to see significant differences in lean meat percentages by underestimating the amount of lean in the carcass. These studies, Boler et al., (2011a, 2012) and
Zamaratskaia et al., (2008) further confirm what was observed in the study by Fuchs et al., (2009), the methods for estimating percent lean meat are underestimating the true percentage of lean in the carcass.
The average advantage of estimated carcass lean of an IC barrow compared with a
PC barrow is 1.05 percentage units (Jaros et al., 2005; Zamaratskaia et al., 2008; Fuchs et al., 2009; Pauly et al., 2009; Gispert et al., 2010; Boler 2011a, 2012) when using various methods of evaluation. These advantages in estimated carcass lean are economically important to not only producers, but packers as well.
Carcass Yield (Dressing Percentage) of Immunologically Castrated Barrows
Carcass yield (dressing percentage) is calculated using the following equation:
Hot Carcass Weight ÷ Live Weight X 100 = Carcass Yield
The advantages in carcass leanness are not the only differences in carcass characteristics between IC and PC barrows. Several peer reviewed research publications have established that dressing percentages of IC barrows are often reduced when
20 compared to PC barrows. Dunshea et al., (2013) conducted a meta-analysis of recently published literature and determined that dressing percentage is decreased in IC barrows by approximately 2 percentage units when compared to PC barrows. It was initially hypothesized that the difference was due to the presence of testicles in the IC barrows, but further research has shown that differences can be attributed to a combination of testicles, associated sex tissues such as bulbourethral glands, seminal vesicles, as well as the thicker skin and larger head present in intact males and IC barrows. Even with the expected advantages in pounds of lean present in IC over PC barrows, the removal of the testicles, associated sex tissues, etc. in IC barrows during slaughter still results in a disadvantage in dressing percentage when compared to PC barrows.
Zamaratskaia et al. (2008) reported a 1.8 percentage unit reduction in dressing percent of IC barrows when compared with PC barrows and a 0.6 percentage unit decrease in dressing percent in intact males when compared with PC barrows. Boler et al., (2011a) reported similar results while determining the effects of different lysine supplementation levels on differences in dressing percentages of IC barrows compared to
PC barrows. Pooled dressing percentage average across lysine inclusion levels was less
(P < 0.05) for IC barrows (71.5%) and intact males at high lysine level (71.4%) than PC barrows at a low lysine level (73.1%). No differences (P > 0.05) were seen in dressing percentages among IC barrows regardless of dietary lysine content. Dressing percentage was greater (P < 0.05) for IC barrows fed medium/high lysine diets (72.0%) when compared with intact males (70.1%). Comparisons of other IC barrows dietary treatment groups were not different (P > 0.05) from the dressing percentages of intact males.
21 Similar results were found by Font i Furnols et al., (2012) regarding differences in dressing percentages between gilts, IC and PC barrows. Live weight at slaughter and carcass weight was not significantly different (P > 0.05) among sexes. The highest (P <
0.05) dressing percentage was for PC barrows (76.9%) and the lowest was for IC barrows
(73.0%). The dressing percentage in IC barrows (73.0%) is lower (P < 0.05) than gilts
(75.7%) and PC barrows (76.9%). These results are similar to previously published literature; IC barrows dressing percentages are reduced by 2.7 percentage units compared to gilts and 3.9 percentage units compared to PC barrows (Font i Furnols et al., 2012).
Boler et al., (2012) evaluated the effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of IC barrows and found a similar decrease in dressing percentage; 2.77 percentage unit decrease (P < 0.001) in IC barrows
(71.78%) compared with PC barrows (74.55%). The magnitude of difference in dressing percentages between IC and PC barrows in this study was greater than in other studies.
Pauly et al., (2009) reported a 1.2 percentage unit difference and Gispert et al., (2010) reported a 2.11 percentage unit difference between IC and PC barrows. Boler et al.,
(2012) obtained an ending live BW in this study 48 hours before slaughter and without a fasting period. Previous research has shown that IC barrows have a greater feed intake compared to PC barrows from post second injection until slaughter (Dunshea et al., 2001,
2011; Fabrega et al., 2010), and therefore the large difference in dressing percentage may be attributed to increased gut fill as well as the previously discussed factors.
Boler et al., (2013) conducted an extensive study aimed at quantifying the differences in dressing percentages between intact males, gilts, IC and PC barrows.
Physically castrated barrows (78.72%) and gilts (78.81%) had the highest dressing
22 percentage of all treatment groups. Intact males (77.40%) and IC barrows (77.29%) had the lowest dressing percentage of all treatment groups. The magnitude of the difference in dressing percentage between IC and PC barrows in Boler et al., (2013), was 1.43 percentage units, which is lower than the differences of 2.76 percentage units and 2.11 percentage units reported by Boler et al., (2011a) and Gispert et al. (2010).
Boler et al., (2013) was able to quantify a large majority of the differences in ending live weight between treatment groups. By weighing and recording the summation of the hot carcass weight, tail, reproductive tracts, full intestinal tract, leaf fat, kidneys, liver, gall bladder, spleen, pluck, neck trim, blood and the head, most of the differences were accounted for between treatment groups. For the IC barrows, 97.96% of the ending live weight was accounted for. For the IC barrows fed RAC, 97.96% of the ending live weight was accounted for. For the PC barrows, 98.24% of the ending live weight was accounted for. For the intact males, 97.50% of the ending live weight was determined and for the gilts, 98.42% of the ending live weight was accounted for (Boler et al., 2013).
The approximately 2 percentage units of ending live weight not accounted for could possibly be due to toenails, hair, and residual blood that was not captured. There were no differences (P > 0.05) among any treatment groups for the tail, gall bladder, spleen, lungs, trachea, or neck trim. There were also no differences (P > 0.05) among any treatments for the percentage of live weight for lungs, trachea, and neck trim (Boler et al.,
2013). However, there were significant differences found in some of the other tissues between treatment groups. The weight of the testicles accounted for 0.28% of the ending live weight in IC barrows and 0.67% of the ending live weight in intact males. This only accounts for a small percentage of the 1.43 percentage unit difference in dressing
23 percentage between IC and PC barrows. When this difference is taken into account, there is still a remaining 0.91 percentage unit difference that can be accounted for in some of the other tissues. Boler et al., (2013) was able to sum the percentage unit differences of these other tissues; gut fill (0.24), testicles (0.28), reproductive tract (0.13), intestinal mass (0.20) and liver/kidney (0.15) accounted for 1.00 percentage units. The remaining
0.43 percentage unit reduction in dressing percentage between IC and PC barrows can be attributed to slight differences in mesenteric tissue, esophagus, trachea, heart, lungs, blood, and the head (Boler et al., 2013). This extensive study has taken a large step towards concluding where the differences in dressing percentages between IC and PC barrows come from.
Carcass Cutting Yields (Cutability) of Immunologically Castrated Barrows
In several peer reviewed research papers (Pauly et al., 2009; Boler et al., 2011b,
2012, 2013) it has been confirmed that IC barrows have heavier boneless trimmed lean product weights in all the major primal cuts except the belly when compared to PC barrows, therefore it is logical to infer that these advantages will translate into greater lean cutting yields and greater carcass cutting yields. Carcass cutability is defined as the amount of boneless, trimmed retail product that can be fabricated from a carcass. A higher carcass cutting yield or cutability can have a major economic impact, translating into higher profits for pork producers and manufacturers.
Bone-in lean cutting yield was calculated with the following equation:
Lean cutting yield =
(Trimmed ham + trimmed loin + Boston butt + Picnic) X100 Chilled right side weight
24 Carcass cutting yield was calculated with the following equation:
Carcass cutting yield =
(Lean cutting yield components + trimmed belly) X100 Chilled right side weight
Pauly et al., (2009) determined the growth performance, carcass characteristics and meat quality of PC barrows, IC barrows and intact male pigs. This study showed that the percentage of the loin as a proportion of the cold carcass weight was the greatest (P <
0.05) in the intact males (25.4%), even though there was no significant difference (P >
0.05) between PC barrows (24.3%) and IC barrows (24.6%), IC barrows were numerically greater. In the ham, intact males (19.0%) and IC barrows (18.9%) were greater (P < 0.05) than PC barrows (18.0%). Similarly, in the shoulder, intact males
(13.1%) and IC barrows (12.9%) were greater (P < 0.05) than PC barrows (12.2%).
However, as anticipated given the principles of allometric growth, when there is an increase in the proportion of parts of the carcass, something has to be sacrificed, and in this case it is the weight of the belly as a proportion of the carcass. An inverse trend is observed in the results of the weight of the belly as a proportion of the cold carcass weight in this experiment. Physically castrated barrows (18.6%) were greater (P < 0.05) than IC barrows (17.9%) and the intact males (17.8%). However, the advantages observed in the lean cuts of IC barrows translated into greater (P < 0.05) lean cutting yields over PC barrows. As anticipated, intact males (57.5%) had the greatest (P < 0.05) lean cutting yield among the treatment groups. However, they were followed by the IC barrows (56.3%), who were significantly greater (P < 0.05) than PC barrows (54.5%) in their lean cutting yields (Pauly et al., 2009).
25 Boler et al., (2011a), determined the effects of dietary lysine supplementation on
IC barrows compared to PC barrows. Intact males (66.09%) had the greatest (P < 0.05) lean cutting yield among all other treatment groups (range 61.51 to 64.08%). The lean cutting yield advantage of intact males was on average more than 2.5 percentage units greater than any other treatment group. Physically castrated barrows (61.51%) had smaller lean cutting yields (P < 0.05) than IC barrows fed medium/high lysine (64.08%),
IC barrows fed high lysine (64.01%), and intact males (66.09%). Immunologically castrated barrows fed medium/high and high lysine had greater (P < 0.05) lean cutting yields than PC barrows by nearly 2.5 percentage units. This study showed that as dietary lysine increased in IC barrow diets, lean cutting yields also increased. When adding the weight of the belly into the equation to calculate carcass cutting yields, similar results were observed. Once again, intact males (77.87%) had the greatest (P < 0.05) carcass cutting yields when compared to the other treatment groups. Physically castrated barrows (73.70%) had lower (P < 0.05) carcass cutting yields (P < 0.05) than IC barrows fed med/high lysine (76.12%), IC barrows fed high lysine (76.33%), and intact males
(77.87%) (Boler et al., 2011a). Once again this study demonstrated that as dietary lysine increased in IC barrow diets, carcass cutting yields also increased. Immunologically castrated barrows fed med/high lysine had a 1.84 percentage unit advantage over IC barrows fed low lysine. Furthermore, this treatment group had a 2.42 percentage unit advantage over PC barrows in terms of carcass cutting yields. These carcass and lean cutting yield results demonstrate that IC barrows need to be fed diets with higher inclusion levels of lysine in order to capture the most advantages over PC barrows.
26 In the paper titled the effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs by Boler et al., (2012), lean and carcass cutting yields were similar to previously published literature. Treatment groups in this study were established based on time of slaughter post-second injection. Two times were established; 4 weeks post-second injection and 6 weeks post-second injection. Immunologically castrated barrows had heavier boneless lean product weights regardless of time of slaughter post-second injection when compared with PC barrows in all of the major primal cuts (Boston butt, picnic, loin, and ham) except the belly. As anticipated, these advantages translated into greater (P <
0.0001) lean cutting yields and greater carcass cutting yields (P < 0.0001) of IC barrows when compared with PC barrows regardless of slaughter time post-second injection
(Boler et al., 2012). Lean cutting yields of IC barrows slaughtered at 4 week post-second injection were 2.61 percentage units greater than PC barrows and carcass cutting yields were 2.47 percentage units greater than PC barrows. Lean cutting yields of IC barrows slaughtered at 6 week post-second injection were 2.63 percentage units greater than PC barrows, and carcass cutting yields were 2.06 percentage units greater than PC barrows.
This resulted in a lean cutting yield advantage of IC barrows being 2.62 percentage units greater (P < 0.0001) than PC barrows and carcass cutting yields being 2.26 percentage units greater (P < 0001) than PC barrows when averaged over both slaughter times (Boler et al., 2012).
Boler et al., (2013) once again observed several differences in carcass cutting yields between IC and PC barrows. Physically castrated barrows (61.48%) had a lower
(P < 0.05) lean cutting yield than IC barrows fed RAC (63.42%), intact males (64.73%),
27 and gilts (62.83%). However, in this experiment, there were no differences between IC barrows (62.48%) and PC barrows. However, IC barrows did have a 1.0 percentage unit numerical advantage in lean cutting yield and 0.7 percentage unit numerical advantage in carcass cutting yield when compared to PC barrows. As stated previously, Boler et al.
(2011, 2012) reported a 2.5 percentage unit advantage in lean cutting yield and carcass cutting yield of IC barrows compared to PC barrows when IC barrows were fed a diet higher in total lysine. In contrast, pigs were in the current study were all fed the same diet and the advantages in lean and carcass cutting yields of IC barrows were not observed when compared to PC barrows. These data, along with previously reported data, further confirm the need for IC barrows to be fed a diet higher in total lysine than normally fed to PC barrows to realize full cutability potential.
Pork Quality of Immunologically Castrated Barrows
Over the years, multiple peer reviewed manuscripts as well as a Zoetis internal report (Tavárez et al., 2013) have concluded that immunological castration does not have any negative effects on pork quality. Ultimate pH, lean color, water holding capacity, and tenderness are not affected by immunological castration and pork quality is not different between IC and PC barrows (Zamaratskaia et al., 2008; Boler et al., 2011a,
2012, 2013; Font i Furnols et al., 2012; Tavárez et al., 2013).
Zamaratskaia et al. (2008) reported no differences in ultimate pH among PC barrows, IC barrows, or intact males in either the LM or the biceps femoris muscles.
Boler et al., (2011a) found similar results, no differences in shear force, cook loss, or ultimate pH among any of the treatment groups (PC fed low lysine, IC fed low lysine, IC fed low/medium lysine, IC fed medium/high lysine, IC fed high lysine, and intact males
28 fed high lysine). Furthermore, this study found no significant differences (P > 0.05) in drip loss between PC barrows and IC barrows fed a similar lysine inclusion level in the diet (Low lysine). D’Souza et al., (2003) also reported no differences (P > 0.05) in drip loss among PC barrows, IC barrows, and intact males. Additionally, Pauly et al. (2009) reported no differences (P > 0.05) for any water-holding capacity characteristics (drip loss, thaw loss, or purge loss) among PC barrows, IC barrows, or intact males fed a similar lysine inclusion level in the diet. Tavárez et al., 2013 also found no differences (P
> 0.05) in drip loss or purge loss percentages between IC and PC barrows.
Font I Furnols et al., (2012) further supports that there are relatively no differences in pork quality between IC barrows and PC barrows. Pork evaluated in this study was of good quality and very similar. With the exception of pH in the SM muscle, there were no significant differences (P > 0.05) in meat quality between gilts, IC and PC barrows. The pH value in the SM muscle was higher (P = 0.0125) in IC barrows compared with gilts.
In the paper titled the effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs by Boler et al., (2012), pork quality results were similar to previously published literature. There were no differences between IC barrows and PC barrows for shear force (P = 0.09), ultimate pH (P = 0.57), a* (P = 0.33), subjective color score (P = 0.64), or drip loss (P =
0.30). Cook loss of chops from PC barrows (21.30%) was less than cook loss of chops from IC barrows (23.47%). However, marbling scores were lower (P = 0.03) in IC barrows compared to PC barrows. Other studies have reported similar disadvantages in marbling scores of IC barrows compared to PC barrows. Boler et al. (2011a) reported no
29 differences in extractable lipid content of the LM between IC and PC barrows when similar lysine levels were included in the diet, but as lysine levels increased in the diet of
IC barrows, extractable lipid levels decreased.
Furthermore, Boler et al., (2013) reported similar results in pork quality attributes between IC and PC barrows. There were no differences among any treatment groups for pork loin cook loss, objective L*, a*, b*, tenderness or subjective color, marbling, and firmness. There were also no differences in ultimate pH among males in the study (IC barrows with and without RAC, PC barrows, or intact males). Gilts, however, had a lower (P < 0.05) loin muscle ultimate pH when compared with IC barrows and IC barrows fed RAC but were similar to PC barrows and intact males. There were no differences (P > 0.05) among treatment groups for drip loss. Physically castrated barrows
(3.01%) had the highest amount of extractible lipid of any treatment group and were 1.02 percentage units higher than intact males (1.99%) which had the lowest amount of extractible lipid of all treatment groups. There were no differences in extractible lipid between IC barrows (2.40%) and IC barrows fed RAC (2.14%). However, PC barrows
(3.01%) had a greater (P < 0.05) amount of extractible lipid than IC barrows (2.40%) and
IC barrows fed RAC (2.14%). These results are similar to what has been seen in previously published literature, IC barrows often have less marbling than PC barrows.
A Zoetis internal report (Tavárez et al., 2013) found similar results in pork quality of IC and PC barrows. The objectives of this study were to evaluate strategies for feeding distillers dried grains with solubles (DDGS) to immunologically castrated barrows.
Treatment groups included IC and PC barrows fed three DDGS feeding programs from weaning to slaughter (0% inclusion (control), 30% inclusion until slaughter or 30%
30 inclusion until 2nd Improvest® injection then reduced to 0% until slaughter (step-down).
No significant differences (P > 0.05) in pH, objective L*, a*, b* color scores, or subjective color and firmness scores between treatment groups. However, similar to previously published literature, IC barrows (1.91) were significantly different (P < 0.05) from PC barrows (2.56) when both fed a 0% inclusion of DDGS or the control group.
Although IC barrows were numerically lower than PC barrows in terms of marbling in the step-down and 30% DDGS treatment groups, there were no significant differences (P
> 0.05) between these treatment groups.
Confirming that the management of pigs using immunologically castration does not have negative effects on pork quality is very important for the implementation of this product in the swine industry. Based on the results of several peer reviewed publications, it has been determined that immunological castration has minimal effects on pork quality parameters.
Sensory Characteristics of Immunologically Castrated Barrows
The last step in the pork supply chain is the consumer. Although this is the last step in the supply chain, consumer acceptability and satisfaction with the pork is the most important variable in the supply chain. Consumers drive the market and dictate the success of the pork industry. Therefore, in order for this product to be successful in the
U.S. swine industry, sensory characteristics must be equal to the sensory characteristics of PC barrows and gilts. It can be inferred that sensory characteristics will not be different between IC barrows and PC barrows since it has been determined that immunological castration is an effective tool rather than physical castration to eliminate boar taint by reducing adrostenone and skatole levels (Dunshea et al., 2001; Zamaratskaia
31 et al., 2008; Font i Furnols et al., 2009) and furthermore pork quality parameters are not different between IC and PC barrows (Zamaratskaia et al., 2008; Boler et al., 2011a,
2012, 2013; Font i Furnols et al., 2012; Tavárez et al., 2013). However, it is still necessary to evaluate the efficacy of this product and validate that sensory characteristics will not be different in IC barrows. Several peer reviewed publications have evaluated consumers’ sensory acceptability of pork from IC barrows (Font i Furnols et al., 2008), as well as trained panels sensory evaluation of pork from IC barrows (Font i Furnols et al.,
2009; Pauly et al., 2010).
Font i Furnols et al., (2008) evaluated consumers’ sensory acceptability of pork from IC barrows compared to pork from gilts, PC barrows, and intact males. Twenty animals of each type were evaluated by 201 consumers in 20 sessions. Longissimus thoracis muscle from the different animals was cooked in an oven at 180 degrees Celsius for 10 minutes (Font i Furnols et al., 2008). Consumers then evaluated the odor and flavor of the meat in a 9 point category scale without an intermediate level. The category scale was as follows; (1) – “Dislike extremely”, (2) – “Dislike very much”, (3) – “Dislike moderately”, (4) – “Dislike slightly”, (6) – “Like slightly”, (7) – “Like moderately”, (8) –
“Like very much”, (9) – “Like extremely”. The medium level, (5) - “neither like nor dislike” was not included to stimulate consumers to commit to either liking or disliking the odor or flavor and not to allow a no opinion response. There were no significant differences (P > 0.05) in the frequency of categories of consumer scores for either odor or flavor for the IC barrows compared to either the PC barrows or the female pigs.
However, the frequency of “dislike” and “dislike a lot” scores for the acceptability of the
32 odor of pork from intact males were significantly greater (P < 0.05) than the other treatment groups (Font i Furnols et al., 2008).
Font i Furnols et al., (2009) went on to further evaluate and characterize the sensory attributes of pork from IC barrows compared to other sex classes as assessed by a trained panel. In this experiment, loins from 24 gilts, 24 intact males, 24 IC barrows and
23 PC barrows were evaluated by eight trained panelists in 24 sessions. Loins were cooked in an oven at 180 degrees Celsius for 10 minutes. Panelists evaluated odor, flavor and texture attributes. Furthermore, loins were evaluated chemically for androstenone and skatole contents. Descriptors were evaluated in an unstructured continuous 10 cm- long scale. Intact males had significantly greater (P < 0.05) odor and flavor scores for androstenone and skatole than gilts, IC and PC barrows. All other treatment groups were relatively similar and were acceptable in their sensory characteristics of odor and flavor.
When texture was considered, meat from intact males had higher hardness scores and lower juiciness scores than IC and PC barrows. This study concluded that from a sensory perspective meat from IC barrows is not different from meat from PC barrows and gilts, but meat from intact males has poor sensory perceptions due to androstenone and skatole odor and flavor.
Further Processed Characteristics of Immunologically Castrated Barrows
Bacon Production
In the United States over 75% of pork is used for further processed products and the most economically important of these is manufacturing bellies into bacon. Currently, the belly primal ($130.53/CWT; Nationalcarlotporkreport.usda.gov; 2/11/2013) of the pig is the most valuable in the pork carcass, therefore researching how immunological
33 castration will affect bacon slicing yields is an area of major importance. It is known that immunologically castrated barrows have a greater proportion of the loin, shoulder and ham (Pauly et al., 2009; Boler et al., 2011b, 2012, 2013), but tend to have thinner bellies and narrower flop distances than physically castrated barrows (Boler et al., 2011b, 2012;
Kyle et al., 2013). Furthermore, when distiller’s grains were added to the diet, IC barrows had a greater concentration of PUFA, which resulted in a greater calculated iodine value (Boler et al., 2012) than physically castrated barrows. Thinner bellies
(Person et al., 2005) and greater PUFA concentrations (Shackelford et al., 1990) caused a reduction in bacon slicing yields. Even though bacon processing characteristics were not different among sexes (Boler et al., 2011b, 2012), there are no data currently available for the effect of immunological castration on commercial bacon slicing yields.
Boler et al., (2011b) evaluated the effects of increasing lysine on further processed product characteristics from immunologically castrated male pigs. This study concluded that bellies derived from IC barrows are an acceptable substitute for raw materials from PC barrows to manufacture bacon. In general, fresh bellies from IC barrows were thinner and softer than fresh bellies from PC barrows, but not as thin or as soft as fresh bellies from intact males. There were no differences in Iodine Values between PC or IC barrows regardless of lysine inclusion. Cook loss percentages of cured bellies from IC barrows were greater than PC barrows, but there were no differences in cooked yield between PC and IC barrows. As anticipated, intact males had the greatest cook loss and least desirable cooked yield for cured bellies among all treatment groups.
Bacon from IC barrows in this population of pigs seemed to be similar to bacon from PC barrows when pigs were fed a conventional corn and soy based diet.
34 In the paper titled the effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs by Boler et al., (2012), bacon characteristics were similar to previously published literature. This study concluded that fresh bellies of IC barrows were thinner and had narrower flop distances (P < 0.05) than PC barrows. The IC barrows took up a greater (P < 0.05) percentage of brine than PC barrows, but lost a greater (P < 0.05) percentage of brine during the curing and smoking process. This resulted in overall no differences (P > 0.05) in cooked yields for cured bellies between IC and PC barrows. Initial data would suggest that fresh bellies from IC barrows should serve as an acceptable substitute for bacon production when compared to PC barrows. However, it is important to consider that these studies were conducted in a laboratory setting, certain variables of production will be different in a commercial setting and therefore further research was needed. Due to fresh bellies from IC barrows being thinner and having narrower flop distances than PC barrows, it was anticipated that bacon production may be hindered in a commercial setting.
Ham Production
Immunological castration produces known changes in production parameters and carcass characteristics of pigs (Dunshea et al., 2013; Pauly et al., 2009; Gispert et al.,
2010; Boler et al., 2011, 2012, 2013), however it does not modify pork quality
(Zamaratskaia et al., 2008; Font I Furnols et al., 2012; Boler et al., 2011a, 2012, 2013), therefore it is logical to infer that it will not have any effect on ham production. Even though hams from IC barrows will make up a larger proportion of the carcass than PC
35 barrows, since pork quality is not sacrificed, it is anticipated that there will be no negative effects on ham production.
Gispert et al., (2010) evaluated carcass and meat quality characteristics of IC barrows, PC barrows, intact males and gilts. As anticipated, intact males (73.05 %) had the greatest (P < 0.05) proportion of the ham represented by muscle. Physically castrated barrows (65.55 %) had the lowest (P < 0.05) proportion of the ham represented by muscle. Gilts (70.45 %) and IC barrows (69.29%) were intermediate and not significantly different (P > 0.05) in terms of proportion of the ham represented by muscle.
Intermuscular fat in the ham was higher in PC and IC barrows (P < 0.05) than gilts and intact males. This paper concluded that in the ham IC barrows are more similar to gilt carcasses than PC barrows. Immunologically castration therefore will provide a good alternative to physical castration for high quality ham production (Gispert et al., 2010).
Boler et al. (2011b) evaluated the effect of immunological castration on further processed product characteristics. As anticipated, intact males (5.58 kg) had the heaviest
(P < 0.05) green weight of the ham among all treatment groups. Green weights of PC barrows (4.80 kg) were not different (P > 0.05) than IC barrows fed low lysine (4.79 kg) or IC barrows fed low/med lysine (5.10 kg), but were significantly lighter (P < 0.05) than
IC barrows fed med/high lysine (5.11 kg) and IC barrows fed high lysine (5.17 kg)
(Boler et al., 2011b). This is another example showing that in order for the advantages of this technology to be captured, nutrition needs to be adjusted to maximize yields. There were no differences (P > 0.05) among treatment groups for pump uptake percentage.
There were also no differences (P > 0.05) in cook loss percentage among any treatment groups. There were no differences (P > 0.05) among any treatment groups for cured ham
36 color for objective L* or a*. Differences (P < 0.05) were seen in objective b* values but the magnitude was very small. There were no differences (P > 0.05) among the treatment groups for break strength. This paper concluded that although there were significant differences (P < 0.05) in green weights of hams between treatment groups, there were no differences among any treatments in cooked loss, protein percentage, or protein fat-free values of cured and smoked hams. Therefore, it can be concluded that it is possible to manufacture high-quality cured and smoked hams from IC barrows (Boler et al., 2011b).
Font i Furnols et al., (2012) concluded that the use of immunological castration is a good alternative to surgical castration for the control of boar taint, moreover it produces known changes in production parameters and carcass characteristics of pigs, but it hardly modifies meat quality and fatty acid composition on fresh meat and dry-cured ham.
Consequently, under the conditions of this study, Duroc pigs managed with improvest are suitable for the production of high quality dry-cured ham.
Ractopamine Hydrochloride and Immunological Castration
Ractopamine hydrochloride (RAC) or (Paylean®), a product by Elanco Animal
Health, was approved in the United States for use in finishing swine diets in 1999.
Ractopamine hydrochloride is an orally administered feed additive that delivered to muscle tissues through the blood stream, where it binds to β-receptors in the muscle cell membranes. This results in an increase in protein synthesis, causing an increase in the proportion of white muscle fibers by increasing intermediate (Type IIA) and white (Type
IIB) myofiber diameter (Aalhus et al., 1992). There are three ways muscle hypertrophy can be influenced by a β-agonist: an increase in muscle protein synthesis, a decrease in protein degradation, or a combination of the two (Mersmann, 1998). Research has shown
37 RAC works by influencing protein synthesis and has little to no effect on protein degradation. Current label claims of RAC require supplementation of 5 to 10 mg/kg for the last 20.4 to 40.8 kg of gain prior to slaughter for pigs weighing over 68 kg and being fed a complete ration containing at least 16% crude protein. Ractopamine is most commonly fed at doses of 5, 7.4, or 10 mg/kg for the last 21 to 35 days prior to slaughter in commercial production systems.
Since its approval, several experiments have been conducted to determine how the product will affect growth, tissue deposition, carcass cutting yields, pork quality, and animal behavior. The product has become popular in the swine industry because it increases weight gain (Apple et al., 2007), improves feed efficiency (Apple et al., 2007), increases carcass leanness (Apple et al., 2007), increases hot carcass weight (Rincker et al., 2009), increases loin eye area (Carr et al., 2008), and increases carcass cutting yields
(Bohrer et al., 2013) when compared to pigs not fed RAC.
Current production systems need to adapt to new technologies in the swine industry. Since ractopamine and immunological castration work through different physiological mechanisms within the pig, it is logical to infer that these two technologies will have an additive effect on growth, tissue deposition, carcass cutting yields, and pork quality. These management techniques offer more challenges and opportunities in production systems. Several peer reviewed publications have studied the interactive effects of these two technologies in production systems.
Rikard-Bell et al. (2009) used 286 pigs consisting of IC barrows, intact males
(190 total males), and gilts (n = 96) to test a step-up RAC program. The experiment fed
RAC to pigs for 31 days prior to harvest where RAC was fed at 5 ppm for 14 days and
38 then increased to 10 ppm for the last 17 days of feeding. The initial dose of immunological castration was given to 96 randomly selected intact males at 11 weeks of age. At 17 weeks of age pigs were assigned to pens based on body weight and back fat thickness within a sex and breed, and second injections were given to the IC group. The study concluded the effects of RAC and immunological castration appear to be additive in improving growth performance and carcass composition (Rikard-Bell et al., 2009).
Ractopamine hydrochloride reduced (P < 0.05) feed intake of IC barrows from 3.04 kg/d for controls to 2.82 for the RAC fed group at day 0 to 14 post second injection when
RAC was fed at 5 ppm. When RAC was included in the diets as a step up program from
5 ppm to 10 ppm over a 31 day feeding period, IC barrows grew 15% more than intact males fed RAC. Immunologically castrated barrows + RAC were 1.90 kg heavier (P <
0.05) than IC barrows not fed RAC. Immunologically castrated barrows had more (P <
0.05) lean (26.5 kg) and less (P < 0.05) fat (4.65 kg) than IC barrows not fed RAC (23.3 kg lean and 7.30 kg of fat). This translated to an advantage in percent lean of 5.8% for IC barrows fed RAC verses IC barrows not fed RAC (Rikard-Bell et al., 2009).
A study by Puls et al., (2013) studied the effects of feeding ractopamine to immunologically and physically castrated barrows, and gilts on pig growth performance.
180 pigs total were used in this study. Genders were PC barrows, IC barrows, and Gilts.
Ractopamine inclusion levels were 0, 5, and 7.5 ppm. The results of this study concluded that there were no gender x RAC interactions for any variables measured, this shows that the response to RAC was similar across genders. Through the duration of the 8 week study, IC barrows had the greatest (P < 0.05) ADG. Overall ADFI was less (P < 0.05) for the gilts than the IC and PC barrows. Overall G:F was greatest (P < 0.05) for IC barrows
39 and least for PC barrows, with the gilts being intermediate. In the 4 week period after the second Improvest dose, IC had 25.2% and 27.8% greater (P < 0.05) ADG, 9.3% and
22.1% greater (P < 0.05) ADFI, and 15.0% and 4.3% greater (P < 0.05) G:F than PC and gilts. These effects were mainly due to gender differences between treatment groups.
Pigs fed RAC at 5 and 7.5 ppm had similar (P > 0.05) growth performances, but had greater (P < 0.05) ADG and G:F and similar (P > 0.05) ADFI compared to pigs fed 0 ppm RAC.
Lowe et al., (2013) continued the previous study, observing the interactive effects of ractopamine and immunological castration on carcass characteristics, yields, and meat quality. Carcasses of IC pigs (104 kg) were 7.4 kg heavier (P < 0.05) than gilt carcasses, but were similar (P > 0.05) to PC carcasses. Immunologically castrated barrows had dressing percentages that were 1.8 and 2.3 percentage units less (P < 0.05) than PC barrows and gilts. Gilts were 0.4 cm leaner (P < 0.05) than IC barrows, which were 0.4 cm leaner (P < 0.05) than PC barrows (Lowe et al., 2013). There were no differences (P > 0.05) between treatment groups for LM area, color, firmness, or pH.
Carcasses of IC barrows had greater (P < 0.05) cutting yields than PC barrows, but were similar (P > 0.05) to gilts. Carcasses from pigs fed 5 and 7.5 mg/kg RAC were 3.7 and
3.2 kg heavier (P < 0.05) than carcasses of control pigs. This study demonstrated that immunological castration and feeding RAC are additive in improving carcass weights.
Boler et al., (2013) found differences in boneless carcass and lean cutting yields between IC barrows fed RAC and IC barrows not fed RAC. Immunologically castrated barrows fed RAC had heavier (P < 0.05) bone-in Boston butts, boneless Boston butts, bone-in trimmed loins, Canadian back loins, tenderloins, sirloins, back ribs, bone-in
40 trimmed hams, inside hams, outside hams, and spareribs than IC barrows not fed RAC.
This resulted in a 1.32 percentage unit advantage (P < 0.05) in boneless lean cutting yield and a 1.48 percentage unit advantage (P < 0.05) in boneless carcass cutting yields of IC barrows fed RAC when compared to IC barrows not fed RAC. These advantages demonstrate that RAC can be used in IC barrows to improve cutability with the same effectiveness as historically observed in physical castrates and gilts.
Bacon Production in the United States
History
Bacon production has a long history dating back to the domestication of pigs.
The earliest record of the domestication of pigs for food dates back to about 7000 B.C. in the Middle East (Alcock et al., 2006). Some historians say that bacon made from hogs was a favorite of the early Romans and Greeks. About 500 years ago, bacon referred to all pork. The term derived from bako (French), bakkon (Germanic), and backe (Old
Teutonic) that refer to the back of the hog (Ayto et al., 1993). European peasants in the
1500's couldn't afford to buy pork often. It was a sign of affluence if a man could "bring home the bacon." They would cut off some for guests and sit around "chewing the fat," now a colloquial term for "having a discussion." The term "bringing home the bacon" now means "earning a living" or "being successful." Bacon is made in many countries of the world. In Germany, it is called speck; Netherlands, spek; France, lard or bacon; Italy, pancetta; and Spain, tocino or tocineta (fsis.usda., 2011). It can be made from several different animal species including pork, turkey, and beef. Bacon can also be made from various parts of an animal and thus its appearance can vary.
41 Manufacturing Pork Bellies Into Bacon
Several steps are involved in producing the common sliced or streaky bacon we are used to in the United States. First each pork belly is skinned and trimmed in order to meet a certain specification. For example, for a carcass to be fabricated to comply with
Institutional Meat Purchase Specification (IMPS) # 408 belly as described by the North
American Meat Processors Association (2010) it must have the spare ribs and teat line removed, and flank end squared. Or it is also common in the U.S. industry to have what is called a natural fall belly, this is when the spare ribs and teat line are removed but the flank end is untrimmed. After curing with salt and nitrite as well as other additives, the pork bellies are heat processed. Mass-produced bacon at the industry level is heat processed in large convection ovens. It is much faster to mass produce bacon using a convection oven (as little as 6 hours) than by traditional smoking, which can take many days. Bacon receives its smoke flavor from natural smoke obtained by smoldering wood chips or by spraying the bacon with a liquid smoke extract. After heat processing and smoking, the bacon must be chilled to below 40 °F before it is sliced (fsis.usda., 2011).
The majority of bacon is sliced before packaging. By adding salt and nitrite, bacon becomes far less perishable than other raw meat products. Even so, the chilling is done quickly to prevent bacterial growth and promote shelf-life of the product. According to
FSIS regulations, the weight of cured pork bellies that are ready for slicing and labeling as "bacon" shall not exceed the weight of the fresh, uncured pork bellies.
Methods of Curing
There are two primary methods of curing bacon: pumping and dry curing.
Pumped bacon has curing ingredients that are injected directly into the meat to speed up
42 the curing process and add bulk. This type of mass-produced bacon is held for curing for
6 to 24 hours before being heated. Dry-cured bacon has a premeasured amount of cure mixture applied or rubbed onto the bacon belly surfaces, completely covering them.
Additional cure may be rubbed in over a number of days, but the amount of added sodium nitrite cannot exceed 200 parts per million (ppm) (fsis.usda., 2011). After the curing phase, the bacon may be left to hang for up to 2 weeks in order for the moisture to be drawn out. Less time is needed if it is going to be smoked. Due to the lengthy processing time and labor required, dry-cured bacon is more expensive than the more mass-produced, pumped bacon. Immersion-cured bacon is placed in a brine solution containing salt, nitrite, and flavoring material or in a container with salt, nitrite, and flavoring material for 2 to 3 days. Sugar, honey, or maple syrup may be added to the brine. The belly must then be left to hang until it is cured.
Common Additives
The most common additives in bacon is salt as a curing agent, and sodium nitrite
(NO2) for its preservative effects as well as characteristic color development. Bacon may also contain other additives such as sugars, maple sugar, wood smoke, flavorings, and spices. Pumped bacon must also contain either ascorbate or sodium erythorbate
(isoascorbate), which greatly reduces the formation of nitrosamines by accelerating the reaction of nitrite with the meat. Sodium nitrite produces the pink color
(nitrosohemoglobin) in cured bacon. Nitrite also greatly delays the development of the
Clostridium botulinum toxin (botulism), develops a cured-meat flavor, retards the development of rancidity, off-odors, and off-flavors during storage, and inhibits the development of a warmed-over flavor (fsis.usda., 2011). Sugar is commonly added to
43 reduce the harsh taste that can be caused by salt. Spices and other flavorings are often added to achieve a characteristic flavor. Most, but not all, cured meat products are smoked after the curing process to impart a smoked meat flavor.
Salt (Sodium Chloride : NaCl)
Salt has many important functions as a food additive and is often considered the most indispensable additive in the curing of meat. The most common form used in production is Sodium Chloride or NaCl. One of the most important functions of salt is to retard bacterial growth. This is primarily the result of the muscle tissue having a higher concentration of salt than the bacterial cells. Most bacterial cell walls are semi-permeable in nature and will allow water but not salt to pass through them. Water will then pass from the less dense to the more dense concentration and the bacterial cell will shrivel
(Ockerman et al., 1996). Salt is also very important as a meat additive due to its desirable flavor. Salt is a pleasant tasting compound that is necessary to the diet (1/2 g/person/day) and instinctively craved by most animals. Salt (NaCl) if placed on the surface of meat during cooking, dehydrates the product and causes the tissue to toughen, which can extend the shelf life of the product. Salt is also incorporated in meat products for its ability to increase water binding in the product by changing the ionic strength of proteins to act as a binding agent. Furthermore, salt can increase water binding during cooking so the final product has improved flavor, juiciness, and tenderness (Terrell et al., 1983;
Ockerman et al., 1996; Desmond et al., 2006). This increased water binding can result in increases in yield and reduced thawing and cooking loss. There are many different varieties of salt that are approved for use by the USDA, including Potassium chloride,
Calcium chloride, and Magnesium chloride, all permitted at 3 percent of the solution.
44 Some common problems with salt inclusion are a harsh taste that is undesirable to certain consumers, dark meat color, and nutritional acceptance (Ockerman et al., 1996).
Sweeteners
Sugars and or artificial sweeteners are often added to cured meat products.
Artificial sweeteners (Saccharin, sodium cyclamate, and calcium cyclamate) only contribute to the flavor of the product (Ockerman et al., 1996). Sugars; normally sucrose, glucose, or corn syrup solids (Max. 2%), corn syrup (Max. 2.5%), glucose syrup (Max.
2%), malt syrup (Max. 2.5%), and sometimes dextrose are used in cured meats. Sugar has several important functions in cured meat products such as bacon. Sugar is very important for its flavor and to counter act the harsh flavor caused by the salt inclusion in the brine. Sugar upon heating tends to caramelize and turn brown and on prolonged heating on a grill will often char. This chemical reaction between an amino acid and a reducing sugar is called The Maillard reaction (Maillard et al., 1912). This gives meat cured with sugar a characteristic color. Also, sugar can retard bacterial growth, but it has to be present at very high levels, usually 20-80 percent concentration.
Nitrate/Nitrite
The USDA is responsible for monitoring the proper use of nitrite by meat processors. While sodium nitrite cannot exceed 200 ppm going into dry-cured bacon, sodium nitrite cannot exceed 120 ppm for both pumped and immersion-cured bacon
(fsis.usda., 2011). A source of nitrite is an essential ingredient in cured meat products. It can be derived from nitrite (NaNO2), potassium nitrite (KNO2) or may be derived from a nitrate compound. Both nitrite and nitrate compounds must be kept in a secure location, as they are both toxic. They are also both sensitive to decomposition and can lose their
45 curing strength and therefore should not be over-stocked. Brines should be made with cold water since warm water can cause nitrite depletion (Ockerman et al., 1996). Nitrite is also important to create the characteristic cured pink meat color. Also, nitrites are highly bacteriostatic and are very important in preserving cured meat products. It has been reported that nitrite may also contribute to the typical cured meat flavor and prevent warmed over flavor. Nitrite can also retard the rate of oxidation of meat fats and this plays a critical role in prolonging shelf life.
Phosphates
Phosphates are used in most cured products to reduce rancidity and increase the water holding capacity. They can be used to increase the brine retention in the belly, which will lead to an increased yield. Also, they are very important as an antioxidant source (Ockerman et al., 1996). Phosphates are limited by the USDA to 0.5% in finished products (Pearson and Tauber 1984). They can be present in several forms such as sodium tripolyphosphate and sodium polyphosphates. They work as water binding ingredients by raising the pH of the meat products, increasing the water binding and increasing yields. Sodium phosphates often have low solubility in water and if used in excess in brines can cause a metallic/soapy flavor in the finished product. Phosphates work as antioxidants by chelating metal ions preventing the initiation of oxidation
(Cassens et al., 1994).
Cure Accelerators
Compounds that lower the pH (acidulants) in cured meat products alter the flavor, reduce bacterial growth, retards the action of many natural enzymes, produce a product with a better sliced shelf life and also accelerate the cured meat color development are
46 known as cure accelerators. Some examples of cure accelerators are ascorbic acid, sodium erythorbate and citric acid. Ascorbic acid and sodium erythorbate are very common and have several functions in a cured product including preventing rancidity, faster color development, resistance to color fading during storage, and reducing residual nitrite levels. They can accelerate the nitrite to nitric oxide reaction accelerating the cured color development and reducing residual nitrite levels (Ockerman et al., 1996).
Also, color development may be reduced from 1-1/2 hours to 15-30 minutes with the addition of cure accelerators. The compounds most widely used to speed up color development are citric acid, gluconodelta lactone (GDL), and fumaric acid in cured meat.
The current FSIS and USDA regulations state that any cure accelerator (usually sodium ascorbate and sodium erythorbate) can only be included at a level of 550 ppm into bacon products (fsis.usda., 2011).
Water
Water is added to most curing formulas and is one of the most important additives. Water serves several functions in a cure solution. Distributing curing ingredients properly will accelerate curing tremendously when compared to dry curing where water is not added. It can also increase the juciness of a product, addition of water counteracts losing water during cooking. Also, since water is inexpensive and the final meat product is priced on a per weight basis the quantity of water added is controlled by regulations (Ockerman et al., 1996).
Cured Meat Color/Reaction
Cured meat color depends on the reaction of nitric oxide (NO) with myoglobin to produce nitrosomyoglobin which is a pinkish red pigment. To obtain nitric oxide,
47 sodium or potassium nitrate and/or sodium or potassium nitrite are added to the curing mixture. To become effective the nitrate must first be reduced to nitrite and this can be accomplished by bacterial reactions (Ockerman et al., 1996). As curing schedules becomes faster the direct addition of nitrite without nitrate is becoming more popular.
The nitrite (NaNO2) is converted to nitrous acid (HNO2) and finally to nitric oxide (NO) which is a gas. Low pH (particularly below 4.6 if no added reducing agents are present), and other reducing conditions in tissue [protein sulfhydryl groups (-SH),reducing coenzymes and other reducing substances] accelerate these reactions which promotes the development of cured meat color and aids in protecting it from fading by light. A reduction in pH by 0.2 to 0.3 will double the reaction rate. All light sources; incandescent (tungsten filament), fluorescent and ultraviolet light have equal effect, provided intensity and exposure are equal, on fading of cured meat color.
Bacon Quality
Although there is not a specific grading system used for bacon, several commercial producers and researchers have cited Person et al., (2005) as a way to classify differences in quality of bacon slices. The bacon ranking system described by
Person et al. (2005) divides bacon classification into three different types: type #1, #2, and #3 slices. Type #1 bacon slices have the cutaneous trunci extending greater than
50% the length of bacon slice and its profile cannot be less than 1.9 cm in thickness.
Type #2 bacon slices have a profile thickness no less than 1.9 cm or have the cutaneous trunci not extending greater than 50% of the length of the bacon slice. Type #3 bacon slices are slices that do not meet any of the previously mentioned characteristics. Pieces falling into the type #3 category generally come from each end of the belly primal, the
48 shoulder or flank ends and are generally classified as “ends and pieces” (Person et al.,
2005). Outside of this grading system, there has been an increasing amount of research on belly length, width, thickness, firmness, flop distance, fatty acid profile analysis, moisture and fat content as a means to evaluate bacon quality.
Due to a large proportion of pork bellies being composed of adipose tissue, the quality of the fat within the belly is extremely important to bacon quality. Fat composition and quality have been studied extensively in the pork industry. Emphasis has been placed on evaluating the degree of saturation and fatty acid content within the belly. Poor lipid composition or a large amount of unsaturated fatty acids has been correlated to softer bellies, leading to poor sliceability, decreased processing yields, and decreased shelf life of bacon (Larsen et al., 2009). Fat that is good in quality has been described as firm and white, while fat that is lower quality is described as soft, oily, wet, grey, and floppy (Hugo and Roodt 2007). Futhermore, when processing bacon, thinner bellies (Person et al., 2005) and greater PUFA concentrations (Shackelford et al., 1990) have been shown to cause a reduction in bacon quality by reducing bacon slicing yields and also hurt consumer perception of the product from a visual standpoint.
Fatty acid composition is very important in characterizing degree of saturation within the belly and determining fat quality. In pork fat there are different classifications of fatty acids, saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) (Hugo and Roodt 2007). The organic structure of these fatty acids dictates the melting and boiling points of the fat, and therefore will determine how the belly will react during processing. Unsaturated fatty acids are characterized by a double bond in their organic structure. In general, fats that are more
49 saturated will have a greater melting point than fats that are highly unsaturated. Several fatty acids are commonly present in pork bellies; (Ockerman et al., 1996) approximate percentage in order from most concentrated to least; Oleic acid
(C18:1)(Monounsaturated)(35-45%), Palmitic acid (C16:0)(Saturated)(20-30%), Linoleic acid (C18:2)(Polyunsaturated) (8-25%), Stearic acid (C18:0)(Saturated)(5-12%),
Palmitoleic acid (C16:1)(Monounsaturated)(2-6%), Myristic (C14:0)(Saturated)(1-4%),
Linolenic (C18:3)(Polyunsaturated)(0.20-1.5%).
In the swine industry today, fatty acids are combined by an equation in an effort to get a value that producers and packers can understand. This value is a calculated iodine value or (IV). Iodine values often are associated with the level of unsaturated fat within the pork carcass. Saturated fat will have a lower IV, while unsaturated fat will have a higher IV. Furthermore, a lower IV is associated with firmer fat and a higher IV is associated with softer fat. Iodine values in pork fat will typically be between 60 and 100
(Hansen 2001). Iodine values are commonly derived by analyzing fatty acids through gas chromatography and then IV is calculated with an equation established by the AOAC in 1984. There are several equations that are used to obtain a calculated IV, however the following equation is used in the majority of published literature. Iodine Value (IV) =
16:1 (0.95) + 18:1 (0.86) + 18:2 (1.732) + 18:3 (2.616) + 20:1 (0.785) + 22:1 (0.723)
(AOAC, 1984). Iodine values can be highly variable because they can be affected by numerous factors including genetics, age, gender, breed, diet, fat thickness, body weight, and variations in fat locations.
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57 Chapter 2: Effects of immunological castration (Improvest®) on further processed belly characteristics and commercial bacon slicing yields of heavy weight finishing pigs
ABSTRACT: The objectives of the experiment were to compare fresh belly characteristics, further processed belly characteristics, and commercial bacon slicing yields of immunologically castrated (IC) barrows, IC barrows fed ractopamine hydrochloride (IC + RAC), physically castrated barrows (PC), intact males, and gilts.
One hundred eighty-eight bellies from pigs slaughtered at 130 kg ending live weight were used in the experiment. Fresh bellies were evaluated for flop distance, length, width, and thickness using a ruler. Fatty acid profiles of belly fat were determined on a piece of fat tissue collected along the dorsal edge from anterior end of the belly. Bellies were frozen and transported to the Ohio State University Meat Science Laboratory after fresh belly characteristic data were collected. Frozen bellies were allowed to thaw, skinned, sorted into treatment groups, and transported to a U.S.D.A federally inspected bacon processing facility for further processing. Bellies were injected with a proprietary brine solution commonly used in bacon production to a target of 113% of green belly weight.
Thermally processed bellies were chilled, weighed, pressed, and sliced according to standard plant protocol. Bellies were sliced for a targeted thickness of 24 slices per kg.
Complete slices were sorted by trained plant personnel and sliced bellies were transported back to Ohio State. The number of slices and a total sliced belly weight was recorded for each belly. Total PUFA percentage of IC barrows (14.71%) was not different (P = 0.20)
58 from PC barrows (14.17%) or gilts (15.46%), but gilts had a greater (P < 0.05) percentage of total PUFA than PC barrows. Differences in total PUFA proportions were reflected in calculated iodine values. There were no differences (P > 0.05) in calculated iodine value among IC barrows (68.26), PC barrows (67.55) and gilts (69.45). Commercial slicing yields calculated by green weight of IC barrows (93.61%) were 4.81 percentage units lower (P < 0.01) than PC barrows (98.42%) and 4.58 percentage units lower (P = 0.01) than gilts (98.19%). Commercial slicing yields (green weight) of IC barrows and intact males (93.31%) were not different (P > 0.05). Ractopamine improved commercial slicing yields (green weight) of IC barrows + RAC by 2.96 percentage units when compared with IC barrows not fed RAC. Commercial slicing yields calculated by cooked weight of IC barrows (90.23%) were 2.66 percentage units lower (P < 0.05) than PC barrows (92.89%) and 2.33 percentage units lower (P < 0.05) than gilts (92.56%).
Commercial slicing yields (cooked weight) of IC barrows and intact males (89.09%) were not different (P < 0.05). Ractopamine improved commercial slicing yields (cooked weight) of IC barrows + RAC by 1.12 percentage units when compared with IC barrows not fed RAC. Overall, fresh belly characteristics of IC barrows appear to be more similar to fresh belly characteristics of gilts than to PC barrows, but commercial slicing yields
(green and cooked) of bacon manufactured from IC barrows are less than both PC barrows and gilts.
59 INTRODUCTION
Immunological castration is a relatively new alternative to physical castration in
U.S. swine production systems. Immunologically castrated (IC) barrows grow faster
(Dunshea et al., 2001; Fàbrega et al., 2010) have leaner carcasses (Jaros et al., 2005;
Schmoll et al, 2009; Fuchs et al., 2009) and greater carcass cutability (Gispert et al.,
2010; Morales et al., 2010; Boler et al., 2011a, 2012) than physically castrated (PC) barrows. Additionally, fresh meat quality characteristics such as drip loss (Pauly et al.,
2009; Boler et al., 2012), cook loss (Pauly et al., 2009; Boler et al, 2011a), ultimate pH
(D’Souza and Mullan, 2003; Pauly et al., 2009; Gispert et al., 2010), and lean color
(Pauly et al., 2009; Boler et al., 2011a, 2012) are not different (P > 0.05) between IC and
PC barrows. Immunologically castrated barrows have a greater proportion of the loin, shoulder and ham, but tend to have thinner bellies and narrower flop distances than physically castrated barrows (Boler et al., 2011b, 2012). Furthermore, when distiller’s grains were added to the diet, IC barrows had a greater concentration of PUFA, which resulted in a higher calculated iodine value (Boler et al., 2012) than physically castrated barrows. Thinner bellies (Person et al., 2005) and greater PUFA concentrations
(Shackelford et al., 1990) caused a reduction in bacon slicing yields. Even though bacon processing characteristics were not different among sexes (Boler et al., 2011b, 2012), there are no data currently available for the effect of immunological castration on commercial bacon slicing yields. Therefore, the objectives of this experiment were to compare fresh belly characteristics, further processed belly characteristics, and commercial bacon slicing yields among IC barrows, IC barrows fed ractopamine hydrochloride (IC + RAC), PC barrows, intact males, and gilts. 60 MATERIALS AND METHODS
No approval was obtained from The Ohio State University Institutional Animal
Care and Use Committee for this experiment because only fresh bellies were used in the experiment. Experimental procedures for the live phase portion of the experiment were reviewed and approved by the University of Illinois Institutional Animal Care and Use
Committee.
Experimental Design
One hundred eighty-eight bellies (n = 188) were obtained from the University of Illinois
Meat Science Laboratory sourced from a previous experiment (Boler et al., 2013). In short, pigs were harvested over a 5 week period. This experiment included PC barrows, intact males, IC barrows; IC barrows + RAC (Paylean, Elanco Animal Health, a division of Eli Lilly) and gilts (Génétiporc G-Performer boars crossed with Fertilis 25 sows;
Génétiporc, Alexandria, MN). Pigs were raised in two blocks consisting of 96 pigs in each block (pigs were housed in pens consisting of 4 pigs per pen; 24 experimental units per block). Four pigs did not complete the live phase portion of the study thus only 188 bellies were available for evaluation. Immunologically castrated barrows received a series of two 2 mL subcutaneous injections of an anti-gonadotropin releasing factor (anti-
GnRF) immunological product (Improvest®; Zoetis, Kalamazoo, MI). The first injection was administered when the pigs were approximately 16 weeks old and the second injection followed 4 weeks later when the pigs were approximately 20 weeks old. Pigs were individually weighed every two weeks prior to the second injection and then each week after receiving the second injection. Any pen of pigs with an average BW of 130
61 kg at 33 d post second injection was humanly slaughtered. The selection process was repeated and pigs were harvested on 33 d, 40 d or 47 d post second injection as they reached an average BW of 130 kg (Boler et al., 2013). Thus, all pigs on the study were harvested over 3 weeks within their respective block.
Fresh Belly Characteristics
Fresh skin-on bellies were sourced from pigs harvested in the summer of 2011
(Boler et al., 2013). Pigs were slaughtered at the University of Illinois Meat Science
Laboratory under the inspection of the USDA FSIS in two blocks over a five week period. Right sides of each carcass were fabricated to comply with Institutional Meat
Purchase Specification (IMPS) as described by the North American Meat Processors
Association (2010). Whole bellies had the spare ribs and teat line removed, and flank end squared to the meet the specifications of an IMPS #408 belly. Bellies were laid flat on a table and covered for 48 hours to allow for temperature equilibration. After equilibration, fresh bellies were evaluated for flop distance, length, and width using a ruler at the midpoint of the longitudinal and cross sectional axis. Thickness was evaluated at eight individual locations across the belly. Measurements one through four were collected along the dorsal edge of belly starting at the anterior end by pushing a sharpened ruler through the skin-side-down belly. Measurements five through eight were collected in the same manner on the ventral side of the belly starting at the anterior end.
Average belly thickness was calculated from the mean of the eight individual measurements. Belly flop distance was determined by measuring the distance between the skin of a belly draped skin-side-down over a stationary bar. A wider flop distance is
62 an indication of a more firm belly and a narrower flop distance is an indication of a less firm belly. A fat tissue sample was collected for fatty acid profile analysis on each belly from the dorsal edge of the anterior end of each belly. Each belly was individually vacuum packaged, frozen, and stored at the University of Illinois meat lab until all pigs were harvested.
Fatty Acid Profiles
Samples were prepared using the Folch method (AOAC, 1984). Fatty acid profiles were determined using a gas chromatograph equipped with a flame-ionization detector assay. Iodine values (IV) were calculated using fatty acid profile data with the following equation: IV = C16:1 (0.95) + C18:1 (0.86) + C18:2 (1.732) + C18:3 (2.616) +
C20:1 (0.785) + C22:1 (0.723) (AOCS, 1998). Total saturated fatty acids (SFA) were calculated using fatty acid profile data with the following equation: SFA = (C12:0) +
(C14:0) + (C16:0) + (C17:0) + (C18:0) + (C20:0) + (C22:0). Total mono-unsaturated fatty acids (MUFA) were calculated using fatty acid profile data with the following equation: MUFA = (C14:1) + (C16:1) + (C17:1) + (C18:1t) + (C18:1c) + (C20:1) +
(C22:1). Total poly-unsaturated fatty acids (PUFA) were calculated using fatty acid profile data with the following equation: PUFA = (C18:2) + (C18:3) + (C20:2) + (C20:3 n3) + (C20:3 n6) + (C20:4). The ratio of unsaturated fatty acids to saturated fatty acids
(UFA:SFA) were calculated using fatty acid profile data with the following equation:
UFA:SFA = (total MUFA + total PUFA) / total SFA. Belly fat samples for IV, SFA,
MUFA, PUFA and UFA:SFA ratio calculations used all 3 fat layers and were collected from a single location on the dorsal edge of the anterior end of the belly.
63 Cured Belly Manufacturing
Frozen vacuum packaged bellies were transported from the University of Illinois to The Ohio State University Meat Science Laboratory after all pigs were slaughtered and fresh belly data were collected. Once at the meat lab at The Ohio State University, bellies were sorted by treatment, skinned, weighed individually to get an initial green weight, repackaged with an identification card attached, and transported to a U.S.D.A federally inspected bacon processing facility for further processing. Bellies were cured with a standard commercial cure solution to target of 113% of initial green weight. Due to commercial confidentiality needs, specific cure ingredients cannot be detailed. Bellies were weighed just after injection to get an individual pump weight and percentage uptake. Trees of bellies were sorted by treatment and weighed by tree after a standardized equilibration period to provide a drain weight and drain percentage loss per treatment. Bellies were then smoked and thermally processed to a target cooked yield of
100% of green weight. Thermally processed bellies were chilled for approximately 48 h prior to slicing to an internal temperature between -5.6 °C and -4.4 °C. Cured and smoked bellies were individually weighed to obtain a cooked weight. Cooked yield was calculated with the equation: (cooked weight / green weight) x 100. Bellies were pressed and sliced according to the U.S.D.A bacon processing plant’s standard protocol. Bellies were sliced starting at the anterior end and working toward to the posterior end for a desired thickness to achieve 24 slices per kg (10 to 12 slices per lb). Complete slices were sorted by plant employees and boxed to maintain anatomical orientation. Ends and incomplete pieces were sorted and placed in a treatment bin. Sliced and boxed bellies were transported back to The Ohio State University meat lab for further analysis. 64 Cured Belly Characteristics
The individual sliced weight of each belly was determined and recorded. Ends and pieces were calculated by subtracting sliced weight from cooked weight. The number of complete slices were counted for each belly and recorded. Commercial slicing yield by green weight was calculated with the equation (sliced weight / green weight) x
100. Commercial slicing yield by cooked weight was calculated with the equation (sliced weight / cooked weight) x 100. Sliced bellies were oriented based on anatomical order from left to right, starting with the blade end and ending with the flank end. Bellies were then divided into five equal zones, with the appropriate number of slices in each zone based on the total number of slices in each particular belly. Zones were designated as A
(blade end), B, C, D, and E (flank end; Robles, 2004). The first two slices in a given zone were used for visual appraisal of shattering and proximate analysis composition.
Shatters were defined as breaks in the fat that occur perpendicular to the length of the slice and not separation of the lean and fat (Salas-Perez, 2002). Slices were packaged and stored for determination of fat and moisture after counting and recording the number of shatters in each given zone. Next, one complete slice was collected from the middle of zones A, C, and E for a total of 3 slices per belly. Slices were identified based on anatomical location as blade end (25% of the length of the belly from the anterior end), middle (50%), and flank end (75%). Slices were laid flat on a white sheet of cardboard with appropriate pig identification and anatomical location of each slice (blade, middle, or flank). The three slices were vacuum packaged as a set, frozen, and stored for image analysis.
65 Proximate Composition
Proximate composition was determined by taking the first two slices in each of the zones A, B, C, D, and E described above and homogenizing in a Cuisinart food processor. A 7 gram sample of the homogenate was oven-dried in duplicate at 100 °C for at least 24 hours to determine percentage moisture. The dried sample was then washed multiple times in warm petroleum ether to determine percentage fat.
Bacon Slice Lean:Fat Image Analysis
Slices were identified based on anatomical location as blade end (25% of the length of the belly from the anterior end), middle (50%), and flank end (75%). Slices were photographed as a set using a Nikon D60 camera (Nikon Instruments Inc., Melville,
NY) at a standardized distance from the samples. Images were converted to a black and white TIFF file in Adobe Photoshop Elements 3.0 (Adobe Systems Inc., San Jose, CA) where the individual slice outlines were selected using the magic wand tool. Image analysis was conducted using National Institutes of Health image processing and analysis in Java software Image-J (Abramoff et al., 2004). A ruler was included in each image to allow for the establishment of known distance. Threshold values were adjusted as needed within each image to account for variations in lean and fat color. Total slice length, width, and area were calculated using Adobe Photoshop Elements 3.0. Secondary lean area [cutaneous trunci (Person et al., 2005)] was calculated by pixel density in Image-J.
66 Statistical Analyses
Data were analyzed with the Mixed procedure of SAS (SAS Institute, 2004) as a general linear mixed model. The fixed effect in the model was treatment (IC barrow, IC barrow + RAC, physical castrate, intact male, gilt). Replication by block interaction was considered a random variable. Homogeneity of variance was tested with the Levene’s test or Brown and Forsythe in the case of non-normal data using the GLM procedure of
SAS. Normality of the residuals was tested in the Univariate procedure of SAS with normal probability plots. Least square means were separated with the PDIFF option.
Statistical differences were accepted as significant at P < 0.05 using a two-tailed test.
Multilinear regression analyses were conducted using the Reg procedure of SAS
(SAS Institute, 2004) to determine a predictive equation for commercial slicing yield.
The initial regression model included candidate independent variables of length, width, flop distance, belly thickness, belly green weight, iodine value, total SFA concentration, total MUFA concentration, total PUFA concentration, ratio of UFA to SFA, belly moisture, and belly fat. Multicollinearity among independent variables was determined using a variance inflation factor (VIF) statistic. It was determined that total SFA concentration, total MUFA concentration, total PUFA concentration, UFA to SFA ratio, and iodine value all had a VIF statistic > 10 (highly collinear). Thus all except iodine value were removed from the model. The final regression model included the following candidate independent variables: length, width, flop distance, belly thickness, belly green weight, iodine value, belly moisture, and belly fat. Influence of individual observations on the estimated value was determined using the Difference of Fit (DFITTS) statistic.
67 Observations were determined to have excessive influence on the estimation of the regression parameters when DFITTS ≥ 2 (√p / n). Five observations met this criterion and were removed from the data set. Independent variables were removed from the final model using a stepwise selection method. Independent variables were required to have a significant F statistic at the SLENTRY and SLSTAY level = 0.15 to be included and remain in the final model. Pearson correlation coefficients were determined using the
Corr procedure of SAS (SAS Institute, 2004).
RESULTS AND DISCUSSION
Fresh Belly Characteristics
Fresh belly characteristics of IC barrows appeared to be similar to fresh belly characteristics of gilts (Table 1). There were no differences (P > 0.05) among any treatments for belly length and no differences in belly width among IC barrows, PC barrows, intact males, and gilts. Immunologically castrated barrows + RAC had the widest (25.46 cm) bellies among all treatment groups. As anticipated, PC barrows (3.94 cm) had the thickest bellies (P < 0.05) and intact males (3.32 cm) had the thinnest bellies
(P < 0.05) among all treatment groups (Table 1). Interestingly, there were no differences
(P > 0.05) in belly thickness among IC barrows (3.74 cm), IC + RAC (3.60 cm), and gilts
(3.64 cm), further implying fresh belly characteristics of IC barrows were more similar to gilts than PC barrows. Physically castrated barrows had wider (P < 0.05) flop distances
(32.23 cm) than all other treatment groups. Immunologically castrated barrows (25.27 cm) had flop distances that were 6.96 cm narrower (P < 0.05) than PC barrows. There were no differences (P > 0.05) in flop distances between IC + RAC (19.43 cm) and gilts
68 (20.78 cm). Intact males had the narrowest (least desirable) belly flop distance (13.17 cm) and were 12.10 cm narrower (P < 0.05) than IC barrows (Table 1). No previous literature has compared IC barrows with gilts. However, Boler et al. (2011) reported that bellies from IC barrows were generally thinner than PC barrows, but thicker than intact males. Based on no differences in belly thickness (P = 0.38) and relatively similar, though statistically different (P = 0.04), flop distances (bellies from IC barrows were actually more firm than gilts) fresh belly characteristics are likely more similar to gilts than to PC barrows.
Fatty Acid Profile
There were no differences (P < 0.05) among any treatment groups for C12:0,
C18:1t, C20:0, C20:1, C22:0, C20:3 n3, C20:3 n6, C20:4, C20:5, C22:1 (Table 2). Gilts
(1.42%) had a lower (P < 0.05) percentage of C14:0 than all other treatment groups, but this only represents a small percentage of the fatty acid profile. Palmitic acid (C16:0) makes up the largest proportion (over 20%) of pork fat’s total saturated fatty acid profile in PC barrows, intact males, and gilts (Barton-Gade, 1987). Wood et al. (1985) reported fatter carcasses tended to have a greater percentage of total SFA, particularly of C16:0 fatty acid. The increase of C16:0 fatty acid percentage of fatter pigs is due in large part to de nova fat synthesis of SFA (Kloareg et al., 2007). Boler et al. (2013) reported that
PC barrows had the greatest amount of 10th rib back fat thickness, intact males had the least amount of 10th rib back fat thickness, and IC barrows, IC + RAC, and gilts were all intermediate. Belly thickness data in the current study parallel those of Boler et al.
(2013) in that PC barrows had the thickest bellies, intact males had the thinnest bellies, and IC barrows, IC + RAC, and gilts were intermediate. This provides sufficient
69 evidence to conclude physically castrated barrows were the fattest pigs and intact males were the leanest pigs in the experiment. Even so, C16:0 percentages were not different
(P > 0.05) among IC barrows, PC barrows, and intact males (Table 2). Similarly, Boler et al., (2011b, 2012) reported no differences in C16:0 fatty acid percentage among physically castrated barrows and IC barrows regardless of lysine level or time of slaughter post-second injection. Immunologically castrated barrows (20.54%) had a greater (P < 0.05) percentage of C16:0 than gilts (19.55%; Table 2). However, C16:0 percentage of IC barrows + RAC (19.87%) were not different (P < 0.05) than intact males
(20.08%) or IC barrows (20.54%). Intact males numerically had the lowest percentage of
C18:0 (10.64%), but was not significantly different (P > 0.05) from IC + RAC (11.14%) and IC barrows (11.26%). There were no differences (P > 0.05) among IC barrows; IC +
RAC, PC barrows, and gilts for C18:0. A mono-unsaturated fatty acid, C18:1c, represents the largest proportion (over 40%) of pork fat’s total fatty acid profile (Barton-
Gade, 1987). The lowest percentage (P < 0.05) of C18:1c was the intact males (42.51%).
Immunologically castrated barrows + RAC (43.79%) had a lower (P < 0.05) percentage of C18:1c than PC barrows (44.89%) or gilts (44.77%; Table 2). There were no differences in the percentage of C18:1c among IC barrows, PC barrows, and gilts (Table
2). Intact males (16.06%) had the greatest percentage of C18:2 among all other treatment groups. Immunologically castrated barrows + RAC (15.02%) had a greater percentage (P
< 0.05) of C18:2 than all remaining treatment groups. Gilts (14.56%) had a 1.15 percentage unit greater (P < 0.05) proportion of C18:2 than PC barrows (13.41%).
Immunologically castrated barrows (13.90%) were intermediate to PC barrows and gilts and were not statistically (P > 0.05) different from either (Table 2).
70 As expected, PC barrows (34.03%) had a greater (P < 0.05) percentage of total SFA than
IC barrows + RAC, intact males, and gilts (Table 2). However, there were no differences
(P > 0.05) in the total SFA concentration of IC (33.62%) and PC barrows. This was not surprising and mostly expected as total SFA concentrations between IC and PC barrows were similar even when pigs were harvested at different intervals post-second injection
(Boler et al., 2012) or when total dietary lysine was manipulated (Boler et al., 2011b).
On the other hand, differences in total PUFA percentages were somewhat unexpected in some cases. Physically castrated barrows (14.17%) had numerically the lowest percentage of total PUFA and intact males (17.08%) had the greatest (P < 0.05) percentage of total PUFA among all treatment groups (Table 2). Interestingly, the PUFA percentage of PC barrows was 1.29 percentage units less (P < 0.05) than the PUFA percentages of gilts (15.46%), but IC barrows (14.71%) were intermediate to PC barrows and gilts and not statistically different (P > 0.05) from either treatment (Table 2).
The high PUFA percentage in intact males belly fat directly contributed to a greater (P <
0.05) calculated iodine value (70.58) than IC barrows, PC barrows, and gilts. There were no differences (P > 0.05) in calculated iodine value among IC barrows (68.26), PC barrows (67.55), and gilts (69.45). Ractopamine hydrochloride increases calculated iodine value of barrows (physical castrates) and gilts (gilts) by 1.94 iodine value units
(Bohrer et al., 2013). Therefore, the 1.52 iodine value unit differences between IC barrows and IC + RAC (69.78) were mostly expected.
Cured Belly Characteristics
There were no differences (P > 0.05) among any treatment groups for pump uptake percentage or cooked yield (Table 3). Differences among treatments groups for
71 green weight, pumped weight, and cooked weight were reflective of primal yield differences reported by Boler et al. (2013). Neither previous study reported differences in processing characteristics of IC barrows when compared with physically castrated barrows (Boler et al., 2011b, 2012).
Number of Slices and Slicing Yields
This was the first experiment to evaluate the slicing yields of bellies from IC barrows when compared with both physically castrated barrows and gilts during commercial processing. Teat lines were removed and flank ends were trimmed prior to processing. Therefore, lean content was greater in these bellies than many used in commercial bacon processing and brine uptake was greater than expected. So, cooked yields of all treatment groups were greater than 100% of green weight (Table 3); therefore, overall slicing yields (regardless of treatment) were greater than anticipated.
None the less, relative differences should still be apparent. There were no differences (P
> 0.05) among treatment groups for the weight of the ends and pieces or the number of slices from each belly. Commercial slicing yields calculated by green weight, however, were greatest among PC barrows (98.42%) and gilts (98.19%). Slicing yields (green weight) of IC barrows (93.61%) were 4.81 percentage units less (P < 0.05) than PC barrows and 4.58 percentage units less (P < 0.05) than gilts. Adding RAC to diets of IC barrows ameliorated some of the negative effects of immunological castration on commercial slicing yields (green weight) and improved commercial slicing yields (green weight) of IC barrows + RAC (96.37%) by 2.76 percentage units. Additionally, commercial slicing yields calculated by cooked weight were greatest (P < 0.05) among
PC barrows (92.89%) and gilts (92.56%). Slicing yields (cooked weight) of IC barrows
72 (90.23%) were 2.66 percentage units less (P < 0.05) than PC barrows and 2.33 percentage units less (P < 0.05) than gilts. Including RAC in the diets of IC barrows ameliorated some of the negative effects of immunological castration once again on commercial slicing yields (cooked weight) and improved commercial slicing yields (cooked weight) of IC barrows + RAC (91.35%) by 1.12 percentage units. As reported previously, thinner bellies (Person et al., 2005), and greater PUFA concentrations (Shackelford et al., 1990) will potentially reduce bacon slicing yields. Differences in belly thickness, and PUFA percentages were not statistically different between IC barrows and physically castrated barrows but, the additive effects of the two parameters appeared to negatively influence commercial slicing yields of bacon from IC barrows when compared with PC barrows.
Additionally, intact males, which had the thinnest bellies and greatest PUFA percentage also had lower (P < 0.05) sliced yields (green weight) (93.31%) when compared to PC barrows and gilts, but were not significantly different (P > 0.05) than IC barrows
(93.61%) or IC barrows + RAC (96.37%).
Variability of bacon slicing yields
Statistical mean differences among treatment groups are very important for defining an experimental population, but the variation associated with those means are equally important. Variation in commercial slicing yields of IC barrows, PC barrows, intact males, and gilts are presented over green weight (Figure 1) and cooked weight
(Figure 2). Slicing yields from IC barrows + RAC were omitted from both figures because there was 1 less replicate per block for that treatment group relative to the other 4 treatment groups. Standard deviations (σ) were calculated by taking the square root of
73 ∑( ̅) the variance using the following equation: √ . The Y-axis shows the
number of bellies that fall within a 5 percentage range of commercial slicing yields shown on the X-axis. There appeared to be variation in commercial slicing yields among the 4 represented treatment groups. Physically castrated barrows (σ = 4.01) had the least variation in commercial slicing yields when expressed as a percentage of green weight.
Gilts (σ = 5.21) were next followed by IC barrows (σ = 8.02) and the intact males (σ =
12.00) had the greatest variation in commercial slicing yields (Figure 1). These results were not entirely unexpected. Physically castrated barrows also had thicker bellies (P <
0.05) than intact males and gilts and were numerically (P > 0.05) than IC barrows.
Additionally, PC barrows had a lower (P < 0.05) concentration of PUFA than intact males and gilts. As stated earlier, thinner bellies (Person et al., 2005) and greater PUFA concentrations (Shackelford et al., 1990) reduce slicing yields, but it also appears these two parameters also increase variability in commercial bacon slicing yields.
It is important for bacon processors to understand variability due to differences in raw materials, but variation in slicing yield can also be added due to inherent variation in the production process itself. Therefore, variability in commercial slicing yields as a proportion of cooked weight is also reported (Figure 2). It becomes apparent that when the variation in processing is removed, the variation in slicing yields is reduced.
Physically castrated barrows (σ = 2.84) and the gilts (σ = 4.84) still had less variation than IC barrows (σ = 5.52), but when variation due to processing was removed intact males had the greatest reduction in slicing yield variation (σ = 3.46). Some of the variation of the gilt and IC barrow treatment group may be due a single belly in each
74 respective treatment group having a very low slicing yield (≤ 65%). In this experiment where a relatively low number of samples (n ~ 40); a single observation can have significant influence on variation.
Pearson correlation coefficients for commercial bacon slicing yields (green weight)
Pearson correlation coefficients were used for commercial bacon slicing yields
(green weight) with fresh belly characteristics (Table 4). Bacon moisture percentage had the largest correlation (r = -0.30; P ≤ 0.001) among all belly characteristics. Bacon fat percentage (r = 0.25) and belly flop distance (r = 0.18) each had a strong relationship (P ≤
0.001) with commercial slicing yield (green weight). Total PUFA percentage (r = -0.19) and average belly thickness (r = 0.27) were also related to commercial slicing yield
(green weight) (Table 4). When a stepwise regression equation was developed to predict commercial slicing yields (green weight) of trimmed, squared, and pressed bellies, only
36% of the variation in commercial slicing yield (green weight) could be accounted for with the equation: 77.7998 + 0.1273(flop distance) + 2.4433(average belly thickness) +
1.4374(green weight). This further confirmed that several factors were potentially contributing to differences in slicing yields of commercially produced bacon.
Pearson correlation coefficients for commercial bacon slicing yields (cooked weight)
Pearson correlation coefficients were used for commercial bacon slicing yields
(cooked weight) with fresh belly characteristics (Table 5). Bacon moisture percentage had the largest correlation (r = -0.30; P ≤ 0.001) among all belly characteristics. Bacon fat percentage (r = 0.20) and belly flop distance (r = 0.19) each had a strong relationship
(P ≤ 0.001) with commercial slicing yield (cooked weight). Total PUFA percentage (r =
75 -0.21) and MUFA percentage (r = 0.22) were also strongly related (P ≤ 0.001) to commercial slicing yields (cooked weight) (Table 5).
Bacon Composition
Physically castrated barrows had the lowest (P < 0.05) percentage of moisture
(47.64%), and the greatest (P < 0.05) percentage of fat (36.97%) among all treatment groups (Table 3). Intact males had the greatest (P < 0.05) percentage of moisture
(56.84%) and the least amount of fat (23.95%) among all treatment groups.
Immunologically castrated barrows (50.45%) had less (P < 0.05) moisture than IC + RAC
(52.56%) and gilts (52.29%). There were no differences (P > 0.05) in fat content among
IC barrows (32.16%), IC + RAC (30.82%), and gilts (30.01%; Table 3).
Bacon Slice Lean:Fat Image Analysis
Blade Section Total slice length was analyzed through the middle of the slice from tip to tip. Physically castrated barrows (23.12 cm) had the smallest total slice length in the blade section, but they were followed closely (P > 0.05) by the intact males (23.20 cm) and the IC barrows (23.50 cm). The IC + RAC (24.19cm) group had the longest (P <
0.05) total slice length. In the blade section, the intact males (3.36 cm) had the least width, but they were not different (P > 0.05) from the IC barrows (3.55cm). Gilts (3.90 cm) had the greatest total slice width, but were not different (P > 0.05) from PC barrows
(3.82 cm) or IC + RAC (3.83 cm). Intact males (82.36 cm2) had the least (P < 0.05) total slice area in the blade section. Immunologically castrated barrows + RAC (98.97cm2) had the greatest total slice area in the blade section, but were not different (P > 0.05) from gilts (97.65cm2), or PC barrows (93.5cm2). The PC barrows (52.81) had the least lean:fat ratio in the blade section. Intact males (62.07) had the greatest lean:fat ratio in the blade
76 section, however were not different (P > 0.05) from IC + RAC (59.21%), or IC barrows
(59.19%). (Table 6)
Middle Section Intact males (22.32cm) had the least total slice length (P < 0.05).
Next were the PC barrows (22.98cm), but were not significantly different (P > 0.05) from
IC barrows (23.18cm) or gilts (23.26cm). Immunologically castrated barrows + RAC
(23.7cm) had the longest total slice length, but were not different (P > 0.05) from gilts
(23.26 cm). Intact males (3.31cm) had the least amount of width, but were not different
(P > 0.05) from the gilts (3.46 cm). The gilts (3.46cm) were not different (P > 0.05) from the IC barrows (3.52 cm), or the IC barrows + RAC (3.60 cm). Physically castrated barrows (3.80 cm) had the widest slice width (P < 0.05). Intact males (82.1cm2) had the least (P < 0.05) total slice area. The IC + RAC (95.68 cm2) group had the greatest total slice area, but were not different (P > 0.05) from the PC barrows (94.60 cm2). Physically castrated barrows (40.73) had the least lean:fat ratio in the middle section, but were not different (P > 0.05) from the IC + RAC (44.12) or IC barrows (45.20). Furthermore, no significant differences (P > 0.05) were found among the other treatments.
Flank Section No significant differences (P > 0.05) were found between the gilts
(22.78cm), PC barrows (23cm), intact males (23.46cm), IC barrows (23.52cm).
However, IC + RAC (23.9cm) had the longest (P < 0.05) total slice length. In the flank section, total slice width values were greater than in the blade or middle section. The intact males (4.06cm) had the narrowest slice width (P < 0.05). Numerically, IC + RAC
(4.88cm) had the greatest slice width, but were not significantly different (P > 0.05) from the PC barrows (4.81cm). The intact males (95.75cm2) had the least total slice area in the flank section, but were not significantly different (P > 0.05) from the gilts (99.39cm2).
77 Greater belly thickness in the flank section (Table 1), translates to a wider slice width, leading to an increase in total slice area in the flank section of the belly. The IC + RAC
(112.3cm2) group had the largest total slice area (P < 0.05) in the flank section. The PC barrows (51.57) had the least lean:fat ratio in the flank section, but they were not significantly different (P > 0.05) from the IC barrows (54.1). The intact males (59.88%) had the greatest lean:fat ratio in the flank section, but were not different (P > 0.05) from the IC + RAC (57.18; Table 6).
Average Immunologically castrated barrows + RAC (23.93 cm) had the longest total slice length (P < 0.05) among all treatment groups. These results were anticipated since fresh belly widths of IC + RAC were wider (P < 0.05) than all other treatment groups (Table 1). The added width of the IC + RAC belly translates to a longer total slice length (23.93 cm) and a larger total slice area (102.4 cm). No differences (P > 0.05) in total slice length were noted among the remaining treatment groups. As anticipated, intact males (3.58 cm) had the least total slice width (P < 0.05). Immunologically castrated barrows (3.89 cm) and gilts (3.95 cm) were not different (P > 0.05) and were intermediate in terms of total slice width. Finally, PC barrows (4.14 cm) had the greatest total slice width, but were not different (P > 0.05) from the IC + RAC (4.11 cm). These results were also anticipated, as the PC barrows and IC + RAC had thicker bellies (Table
1), which ultimately translated to greater total slice width. Differences in length and width reported above, directly related to the differences in total slice area. Intact males
(86.65 cm2) had the least (P < 0.05) total slice area compared to all other treatments.
Immunologically castrated barrows (94.2 cm2) total slice area was not different (P > 0.05) from gilts (94.87 cm2). Physically castrated barrows (98.23 cm2) had intermediate total
78 slice area, but were not different (P > 0.05) from the IC barrows (94.2 cm2), gilts (94.87 cm2), or IC + RAC (102.4 cm2). Immunologically castrated barrows + RAC (102.4 cm2) had the greatest total slice area, but were not different (P > 0.05) than PC barrows (98.23 cm2). As anticipated, PC barrows (48.37) had the least (P < 0.05) lean:fat ratio when compared to all other treatment groups. Intact males (57.24) had the greatest (P < 0.05) lean:fat ratio when compared to all other treatment groups. Immunologically castrated barrows (52.83), IC + RAC (53.47), and gilts (53.61) were not different (P > 0.05) and were intermediate in their lean:fat ratios.
Conclusions
Fresh belly characteristics from IC barrows appear to be more similar to fresh belly characteristics of gilts than to PC barrows in some categories. Physically castrated barrows had thicker bellies than all treatment groups except IC barrows. Average belly thickness of bellies from IC barrows and gilts were not different. Total PUFA percentages were not different between IC and PC barrows. Total PUFA percentages were also not different between IC barrows and gilts, but gilts had a greater percentage of
PUFA in belly fat compared to PC barrows. Calculated iodine values were not different and would likely be considered acceptable (< 73) for all treatment groups. Ractopamine increased calculated iodine value of IC barrows by 1.52 iodine value units when compared with IC barrows not fed RAC. Processing characteristics among IC barrows,
PC barrows, and gilts were similar to those reported in previous experiments and did not differ among those three treatment groups. Even so, commercial slicing yields calculated by green weight of IC barrows were approximately 4.5 percentage units less than commercial slicing yields (green weight) of PC barrows and gilts. Ractopamine
79 ameliorated some of the negative effects of immunological castration and improved commercial slicing yields (green weight) by 2.76 percentage units when compared with
IC barrows. Furthermore, commercial slicing yields calculated by cooked weight of IC barrows were approximately 2.5 percentage units less than commercial slicing yields
(cooked weight) of PC barrows and gilts. Ractopamine improved commercial slicing yields by cooked weight of IC barrows + RAC by 1.12 percentage units when compared with IC barrows not fed RAC. Overall, there was less variation in commercial bacon slicing yields among PC barrows and gilts than IC barrows. There were no differences in commercial slicing yields (cooked weight) of IC barrows + RAC, physically castrated barrows, or gilts. Overall, immunological castration does not appear to affect processing characteristics, but may reduce commercial bacon slicing yields of whole bellies with the spare ribs and teat line removed, and the flank end squared.
80 LITERATURE CITED
Abramoff, M. D., P. J. Magelhaes, and S. J. Ram. 2004. Image processing with ImageJ. Biophotonics Intl. 11: 36-42.
AOCS. 1998. Official methods and recommended practices of the AOCS (5th ed.). Champaign, Illinois: American Oil Chemist Society.
Apple, J.K., J.T. Sawyer, C.V. Maxwell, J.W.S. Yancey, J.W. Frank, J.C. Woodworth, and R.E. Musser. 2011. Effects of L-carnitine supplementation on quality characteristics of fresh pork bellies from pigs fed 3 levels of corn oil. J. Anim. Sci. 89: 2878-2891.
Barton-Gade, P.A.,1987. Meat and fat quality in boars, castrates, and gilts. Livest. Prod. Sci. 16: 187-196
Bohrer, B.M., J.M. Kyle, D.D. Boler, P.J. Rincker, M.J. Ritter, and S.N. Carr. 2012. Review: Meta-analysis of the effects of ractopamine hydrochloride on carcass cutability and primal yields of finishing pigs. J. Anim. Sci. submitted.
Boler, D.D., L. W. Kutzler, D. M. Meeuwse, V. L. King, D. R. Campion, F. K. McKeith, and J. Killefer. 2011a. Effects of increasing lysine on carcass composition and cutting yields of immunologically castrated male pigs. J. Anim. Sci. 89: 2189- 2199.
Boler, D.D., D.L. Clark, A.A. Baer, D.M. Meeuwse, V.L. King, F.K. McKeith, and J. Killefer. 2011b. Effects of increasing lysine on further processed product characteristics of immunologically castrated male pigs. J. Anim Sci. 89: 2200- 2209.
Boler, D D., J. Killefer, D.M. Meeuwse, V.L. King, F.K. McKeith, and A.C. Dilger. 2012. Effects of slaughter time post-second injection on carcass cutting yields and bacon characteristics of immunologically castrated male pigs. J. Anim. Sci. 90: 334-344.
Boler, D.D., C.L. Puls, D.L. Clark, M. Ellis, A.L. Schroeder, P.D. Matzat, J. Killefer, F.K. McKeith, and A.C. Dilger. 2013. Effects of immunological castration on
81 changes in dressing percentage and carcass characteristics of heavy weight finishing pigs. J. Anim Sci. submitted.
D'Souza, D. N. and B. P. Mullan. 2003. The effect of genotype and castration method on the eating quality characteristics of pork from male pigs. Anim. Sci. 77:67-72.
Dunshea, F. R., C. Colantoni, K. Howard, I. McCauley, P. Jackson, K. A. Long, S. Lopaticki, E. A. Nugent, J. A. Simons, J. Walker, and D. P. Hennessy. 2001. Vaccination of boars with a GnRH vaccine (Improvac) eliminates boar taint and increases growth performance. J. Anim Sci. 79: 2524-2535.
Fàbrega, E., A. Velarde, J. Cros, M. Gispert, P. Suárez, J. Tibau, and J. Soler. 2010. Effect of vaccination against gonadotropin-releasing hormone, using Improvac®, on growth performance, body composition, behavior and acute phase proteins. Livest. Sci. 132: 53-59.
Fuchs, T., H. Nathues, A. Koehrmann, S. Andrews, F. Brock, N. Sudhaus, G. Klein, and E. grosse Beilage. 2009. A comparison of the carcase characteristics of pigs immunized with a 'gonadotropin releasing-factor (GnRF)' vaccine against boar taint with physically castrated pigs. Meat Sci. 83: 702-705.
Gispert, M., M. Àngels Oliver, A. Velarde, P. Suarez, J. Pérez, M. Font i Furnols. 2010. Carcass and meat quality characterisitcs of immunocastrated male, physically castrated male, entire male, and female pigs. Meat Sci. 85: 664-670.
Jaros, P., E. Bürgi, K. D. C. Stärk, R. Claus, D. Hennessy, and R. Thun. 2005. Effect of active immunization against GnRH on androstenone concentration, growth performance and carcass quality in intact male pigs. Livest. Prod. Sci. 92: 31-38.
Kloareg, M., J. Noblet, and J. van Milgen. 2007. Deposition of dietary fatty acids, de novo synthesis and anatomical partitioning of fatty acids in finishing pigs. Br. J. Nutr. 97:35–44.
Morales, J., M. Gispert, M. Hortos, J. Pérez, P. Suárez, and C. Piñeiro. 2010. Evaluation of production performance and carcass quality characteristics of boars immunized against gonadotropin-releasing hormone (GnRH) compared with physically castrated male, entire male, and female pigs. Spanish J. Agric Research. 8: 599- 606.
North American Meat Processors Association. (2010). The Meat Buyer’s Guide. 6th ed. North American Meat Processors Assocition, Reston, VA.
82 Pauly, C., P. Spring, J. V. O'Doherty, S. Ampuero Kragten, and G. Bee. 2009. Growth performance, carcass characteristics and meat quality of group-penned physically castrated, immunocastrated (improvac) and entire male pigs and individually penned entire male pigs. Animal. 3: 1057-1066.
Person, R.C., D.R. McKenna, D.B. Griffin, F.K. McKeith, J.A. Scanga, K.E. Belk, G.C. Smith, and J.W. Savell. 2005. Benchmarking value in the pork supply chain: Processing characteristics and consumer evaluations of pork bellies of thickness when manufactured into bacon. Meat Sci. 70: 121-131.
Robles, CC. 2004. The effect of fresh and frozen bellies on bacon processing characteristics and bacon quality. M.S. Thesis. University of Nebraska-Lincoln, Lincoln, NE.
Salas-Perez, PJ. 2002. Differences among breeds, diets, slaughter weights and sex type in the shattering of bacon slices. M.S. Thesis. University of Nebraska-Lincoln, Lincoln, NE.
SAS Institute. (2004). SAS System for Windows Release V9.3.
Schmoll, F., J. Kauffold, A. Pfützner, J. Baumgartner, F. Brock, M. Grodzycki, S. Anderews. 2009. Growth performance and carcass traits of boars raised in Germany and either physically castrated or vaccinated against gonadotropin- releasing hormone. J. Swine Health Prod. 17: 250-25.
Shackelford, S.D., M.F. Miller, K.D. Haydon, N.V. Lovegren, C.E. Lyon, and J.O. Reagan. 1990. Acceptability of bacon as influenced by the feeding of elevated levels of monounsaturated fats to growing-finishing swine. J. Food Sci. 55: 621- 624
Wood, J. D., R. C. D. Jones, J. A. Bayntun, and E. Dransfield. 1985. Backfat quality in boars and barrows at 90 kg live weight. Anim. Prod. 40:481–487.
83
0.11
0.03
0.01
0.01
0.09
< 0.01
< 0.01
< 0.01
< 0.001
< 0.001
< 0.001
P P - value
< 0.0001
1.76
0.11
0.14
0.16
0.11
0.11
0.16
0.10
0.14
0.16
0.42
0.48
SEM
b
a
b
c
b
ab
bc
ab
ab
ab
ab
Gilt
3.64
4.24
3.44
61.59
3.39
3.16
3.08
3.07
3.97
4.76
20.78
23.44
a
a
a
a
a
a
a
a
a
a
a
3.32
3.61
3.09
3.07
2.69
2.86
2.93
3.79
4.50
Male
60.41
Intact Intact
13.17
23.53
d
a
c
c
c
c
c
c
c
c
b
3.94
4.28
3.82
3.80
3.34
3.35
4.31
5.37
3.22
61.39
32.23
23.61
Barrows
Castrated
Physically
Sex
b
b
b
b
b
ab
ab
ab
bc
abc
abc
3.60
3.36
2.98
62.18
3.83
3.38
2.97
5.03
19.43
25.46
3.11
4.09
IC Barrows IC+ Barrows
Ractopamine
c
a
c
b
b
b
bc
bc
bc
bc
bc
5.15
3.47
3.35
3.31
61.67
3.74
4.03
3.12
3.21
4.26
25.27
24.32
Barrows
Castrated (IC)
Immunologically Immunologically
The effect of immunological castration on fresh belly characteristicson castration The effect finishing of immunological weight of heavy pigs
is from the anterior to posterior position of the ventral edge of the bellyedge of the ventral of the position posterior to anterior the is from
Location 8 Location
Location 7 Location
Location 6 Location
Location 5 Location
Location 4 Location
Location 3 Location
Location 2 Location
Location 1 Location
Location 1 to 4 is from anterior to posterior position of dorsal edge of the belly; Location 5 to 8 5 of dorsal to Location belly; edge position of the posterior to 4 anterior is1 to Location from
Thickness, cm
1
Means within a row for experimental treatments without a common superscript differ (P differ < 0.05) superscript a common without treatments experimental for a Means row within
Flop distance, Flop cm
Average Average thickness
1
Width, cm Width,
Length, cmLength,
Item Table 1.
84
Table 2. The effect of immunological castration on fatty acid profiles of heavy weight finishing pigs Sex Immunologically Physically Castrated (IC) IC Barrow + Castrated Item Barrow Ractopamine Barrow Intact Male Gilt SEM P - value Lauric (12:0), % 0.03 0.01 0.03 0.02 0.01 0.01 0.16 Myristic (14:0), % 1.58b 1.51b 1.58b 1.52b 1.42a 0.03 < 0.01 Palmitic (16:0), % 20.54bc 19.87ab 20.60c 20.08abc 19.55a 0.27 0.01 C16:1, % 2.84c 2.65bc 2.54ab 2.68bc 2.38a 0.10 < 0.01 Stearic (18:0), % 11.26ab 11.14ab 11.66b 10.64a 11.86b 0.28 0.02 C18:1t 0.94 0.96 1.01 0.96 1.03 0.09 0.88 C18:1c 44.48bc 43.79b 44.89c 42.51a 44.77c 0.54 < 0.0001 Linoleic (18:2), % 13.90ab 15.02c 13.41a 16.06d 14.56b 0.50 < 0.0001 Linolenic (18:3), % 0.71a 0.81bc 0.69a 0.85c 0.74ab 0.07 < 0.01 Arachidic (20:0), % 0.04 0.03 0.01 0.01 0.00 0.01 0.09 C20:1, % 0.64 0.67 0.72 0.61 0.68 0.04 0.27 Behenic (22:0), % 0.17 0.19 0.14 0.17 0.11 0.03 0.10 C20:3 n3, % 0.33 0.36 0.29 0.33 0.21 0.04 0.14 C20:3 n6, % 0.08 0.07 0.04 0.06 0.10 0.03 0.44 C20:4, % 0.02 0.00 0.02 0.09 0.05 0.03 0.14 C20:5, % 0.00 0.02 0.01 0.01 0.01 0.01 0.46 C22:1, % 0.07 0.13 0.09 0.15 0.17 0.05 0.28 1Total SFA, % 33.62bc 32.76ab 34.03c 32.46a 32.94ab 0.42 0.03 2Total MUFA, % 48.99bc 48.23b 49.25c 46.95a 49.04bc 0.63 < 0.0001 3Total PUFA, % 14.71ab 15.92c 14.17a 17.08d 15.46bc 0.56 < 0.0001 4UFA:SFA ratio 1.91 1.97 2.03 1.99 1.97 0.08 0.78 5Iodine value 68.26ab 69.78bc 67.55a 70.58c 69.45ab 0.71 < 0.01 Means within a row for experimental treatments without a common superscript differ (P < 0.05) 1Total SFA = (C12:0) + (C14:0) + (C16:0) + (C17:0) + (C18:0) +(C20:0) + (C22:0) 2Total MUFA = (C14:1) + (C16:1) + (C17:1) + (C18:1t) + (C18:1c) + (C20:1) + (C22:1) 3Total PUFA = (C18:2) + (C18:3) + (C20:2) + (C20:3 n3) + (C20:3 n6) + (C20:4) 4UFA: SFA ratio = (total MUFA + total PUFA) / total SFA 5 Iodine value = 16:1 (0.95) + 18:1 (0.86) + 18:2 (1.732) + 18:3 (2.616) + 20:1 (0.785) + 22:1 (0.723)
85
0.09
0.01
0.17
0.76
0.52
0.64
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
<.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
< 0.0001
P P - value
0.95
0.61
2.72
0.73
0.69
1.04
0.74
0.39
0.80
1.41
0.48
1.43
0.13
1.19
0.13
1.27
0.17
0.11
SEM
c
c
b
b
ab
a
b
b
b
b
ab
ab
ab
ab
Gilt
0.38
3.90
4.72
5.11
5.54
4.79
15.67
52.29
4.10
6.30
4.50
1.30
92.56
30.01
98.19
117.30
106.10
20.10
a
d
a
a
a
a
a
a
a
a
a
a
a
a
0.48
2.25
3.28
5.50
3.29
0.88
4.04
4.51
Male
15.22
4.98
4.32
Intact Intact
23.95
56.84
15.21
89.09
93.31
118.40
104.69
c
a
b
c
b
a
c
c
c
b
ab
bc
bc
ab
0.39
4.80
5.03
5.41
5.10
14.90
5.87
4.00
8.40
6.00
1.80
36.97
47.64
25.00
92.89
98.42
117.90
105.97
Barrow
Castrated
Physically
Sex
b
c
a
bc
ab
a
a
a
c
c
b
ab
ab
bc
0.47
2.45
3.42
4.87
5.44
5.11
15.47
5.92
4.29
1.62
4.97
30.82
52.56
16.73
116.14
105.49
91.35
96.37
IC Barrows IC+ Barrows
Ractopamine
c
c
b
b
a
c
ab
b
b
b
b
b
b
bc
0.50
7.51
5.59
6.89
2.21
4.55
5.06
5.74
17.19
32.42
10.20
4.88
32.16
50.45
93.61
116.68
103.79
Barrow
90.23
Castrated (IC)
Immunologically Immunologically
The effect of immunological castration on bacon processing bacon characteristicson castration The effect finishing of immunological weight of heavy pigs
Fat, % Fat,
Moisture % Moisture
Zone E Zone
Zone D Zone
Zone C Zone
Zone B Zone
Zone A Zone
Total number of shatters were counted between 2 slices between counted in eachof shatters were zone Total number
Sliced yield [Cooked wt] = (slicedwt] Sliced yield xweight) [Cooked 100 / weight cooked
Sliced yield [Green wt] = (slicedwt] Sliced yield [Green xweight) / weight green 100
Shatters
Sliced yield (Cooked wt), % wt), Sliced yield (Cooked
Sliced yield (Green wt), % Sliced wt), yield (Green
3
2
1
Means within a row for experimental treatments without a common superscript differ (P differ < 0.05) superscript a common without treatments experimental for a Means row within
Bacon Bacon composition
Total Total Shatters
3
2
1
Ends and Ends Piecesand kg wt,
Number of Slices Number
Sliced wt, kg Sliced wt,
Cooked yield, % Cooked
Cooked wt, kg wt, Cooked
Pump uptake, % uptake, Pump
Pump wt, kg wt, Pump
Green wt, kg wt, Green
Item Table 3.
86
-0.84***
Moisture
0.30***
-0.27***
UFA:SFA
SFA
0.28***
-0.98***
-0.32***
0.17*
MUFA
-0.24**
0.32***
-0.29***
PUFA
0.45***
0.49***
-0.66***
-0.45***
-0.37***
1
IV
-0.22**
0.87***
0.76***
0.43***
-0.73***
-0.36***
0.12
-0.12
0.43***
0.36***
-0.39***
-0.52***
-0.45***
Green Wt Green
Flop
0.54***
0.37***
0.44***
0.60***
-0.58***
-0.64***
-0.41***
-0.71***
0.40
0.15
-0.14
0.59***
0.55***
0.36***
-0.35***
-0.47***
-0.45***
Thickness
0.01
0.04
0.02
0.06
0.07
-0.01
-0.07
0.15*
-0.15*
Width
0.42***
0.13
0.14
0.02
0.10
-0.03
-0.11
0.14*
-0.15*
0.21**
Length
-0.21**
0.60***
0.14
0.12
-0.01
-0.10
0.17*
< 0.01 <
-0.15*
0.27**
-0.19**
0.18***
0.25***
-0.30***
Sliceyield
Pearsoncorrelation coefficients )ofcommercialslicing (r yields (green weight) processing characteristics bacon and
0.001
≤
0.01
0.05
≤
≤
IV = Iodine IV= value
1
*** P ***
** P **
* P P *
Length
Width
Thickness
Flop
Green Wt Green
IV
PUFA
MUFA
SFA
UFA:SFA
Moisture
Fat Table 4. Table
87
-0.84***
Moisture
0.30***
UFA:SFA
-0.27***
SFA
0.28***
-0.98***
-0.32***
0.17*
MUFA
-0.24**
0.32***
-0.29***
PUFA
0.45***
0.49***
-0.66***
-0.45***
-0.37***
1
IV
-0.22**
0.87***
0.76***
0.43***
-0.73***
-0.36***
0.12
-0.12
0.43***
0.36***
-0.39***
-0.52***
-0.45***
Green Wt Green
Flop
0.54***
0.37***
0.44***
0.60***
-0.58***
-0.64***
-0.41***
-0.71***
0.40
0.15
-0.14
0.59***
0.55***
0.36***
-0.35***
-0.47***
-0.45***
Thickness
0.01
0.04
0.02
0.06
0.07
-0.01
-0.07
0.15*
-0.15*
Width
0.42***
0.13
0.14
0.02
0.10
-0.03
-0.11
0.14*
.21**
-0.15*
Length
-0.21**
0.60***
0.10
0.02
0.05
0.14
0.06
-0.13
-0.04
0.19**
0.22**
0.20**
-0.21**
-0.30***
Slice yield
Pearson correlation coefficients ( r ) of commercial slicing yields (cooked and weight) bacon processing characteristics
0.001
≤
0.01
0.05
≤
≤
IV = IodineIV = value
1
*** P ***
** P **
* P *
Length
Width
Thickness
Flop
Green Wt Green
IV
PUFA
MUFA
SFA
UFA:SFA
Moisture
Fat Table 5. Table
88
Table 6. The effects of immunological castration on bacon slice lean to fat ratios of heavy weight finishing pigs Sex Immunologically Physically Castrated (IC) IC Barrows + Castrated Intact Item Barrows Ractopamine Barrows Male Gilt SEM P - value Blade End Total Slice Length cm 23.50ab 24.19c 23.12a 23.20a 23.79b 0.20 < 0.001 Total Slice Width cm 3.55ab 3.83bc 3.82bc 3.36a 3.90c 0.11 < 0.01 Total Slice Area cm2 90.23b 98.97c 93.50bc 82.36a 97.65c 2.15 < 0.0001 Total Lean Area cm2 53.33ab 58.46c 49.36a 51.06a 55.84bc 1.64 < 0.01 Secondary Lean Area cm2 16.51ab 19.26d 14.79a 17.07bc 18.41cd 0.77 < 0.001 Lean:Fat Ratio 59.19bc 59.21bc 52.81a 62.07c 57.19b 1.55 < 0.01 Middle Total Slice Length cm 23.18b 23.70c 22.98b 22.32a 23.26bc 0.18 < 0.0001 Total Slice Width cm 3.52b 3.60b 3.80c 3.31a 3.46ab 0.07 < 0.0001 Total Slice Area cm2 89.84bc 95.68d 94.60cd 82.10a 87.57b 2.12 < 0.0001 Total Lean Area cm2 40.56 42.04 38.47 40.74 41.83 0.63 0.63 Secondary Lean Area cm2 11.63a 13.99c 11.36a 12.58ab 13.21bc 0.53 < 0.01 Lean:Fat Ratio 45.20ab 44.12ab 40.73a 49.67b 47.83b 2.07 0.02 Flank End Total Slice Length cm 23.52a 23.90b 23.00a 23.46a 22.78a 0.33 0.10 Total Slice Width cm 4.59bc 4.88d 4.81cd 4.06a 4.49b 0.09 < 0.0001 Total Slice Area cm2 102.45bc 112.30d 106.61c 95.75a 99.39ab 2.16 < 0.0001 Total Lean Area cm2 55.39a 64.00b 54.89a 57.24a 55.49a 1.25 < 0.0001 Secondary Lean Area cm2 4.04 4.27 3.21 4.60 4.19 0.56 0.40 Lean:Fat Ratio 54.10ab 57.18cd 51.57a 59.88d 55.83bc 1.14 < 0.0001 Average Total Slice Length cm 23.40a 23.93b 23.04a 22.99a 23.28a 0.18 < 0.01 Total Slice Width cm 3.89b 4.11c 4.14c 3.58a 3.95b 0.07 < 0.0001 Total Slice Area cm2 94.20b 102.40c 98.23bc 86.65a 94.87b 1.86 < 0.0001 Total Lean Area cm2 49.76ab 54.85c 47.57a 49.66ab 51.06b 1.31 < 0.01 Secondary Lean Area cm2 10.73ab 12.53c 9.79a 11.39bc 11.94c 0.48 < 0.001 Lean:Fat Ratio 52.83b 53.47b 48.37a 57.24c 53.61b 1.29 < 0.0001 Means within a row for experimental treatments without a common superscript differ (P < 0.05)
89
IC Barrow = 8.02 PC Barrow = 4.01 Intact Male = 12.00 Gilt = 5.21
Figure 1: Variation of commercial bacon slicing yields of immunologically castrated (IC) barrows, physically castrated (PC) barrows, intact males, and gilts when expressed as a proportion of green weight using the mathematical equation: slicing yield (green weight) = (sliced weight / green weight) * 100
90
Figure 2: Variation of commercial bacon slicing yields of immunologically castrated (IC) barrows, physically castrated (PC) barrows, intact males, and gilts when expressed as a proportion of cooked weight using the mathematical equation: slicing yield (green weight) = (sliced weight / green weight) * 100
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