RESEARCH IN PIG BREEDING, 14, 2020 (2)

WHICH HORMONES HELP TO OPTIMIZE PIGLET PRODUCTION?

Wähner, M.

Anhalt University of Applied sciences, Bernburg, Germany

Abstract

Sows are kept and piglet production nowadays generally according to the periodic group farrowing system with the use of artificial insemination. To this end, it is necessary to control the reproductive events in the sows. Their aim is to bring the sows in a group into heat almost at the same time so that they can be inseminated at the same time. This guarantees almost the same farrowing dates for the sows in a group. The most important measure in the sow group is at the end of the suckling period the date for the simultaneous weaning of the piglets from the sows. In order to support the synchronization of the reproductive processes in the sows in a group, the use of exogenous hormones in the respective cycle phases of the animals is recommended. In the article the hormones available for this (biotechnics) are presented with their effects. Reproductive hormones are differentiated according to their place of synthesis and their target organ. This includes the hypothalamus with the target organ pituitary gland (releasing hormone, GnRH), the anterior pituitary lobe with the gonads (, FSH, LH), the posterior pituitary lobe with the smooth muscles (oxytocin) and the sex steroids (prostaglandin) formed on the ovary (corpus luteum) call. As a tissue hormone, prostaglandin F2α is important with regard to its luteolytic effect. Finally, the environmentally relevant importance of hormone treatment in sows is discussed. Currently 10 to 15 percent of sows are treated with hormones. The scope of use of hormonal reproductive control in sows is decreasing.

Key Words: Sows, piglet production, hormones, biotechnology, environmental relevance

In the agricultural sow production for the stages (KÖNIG, 1982). At that time, these production of piglets is working on the principle activities had a relationship to the large, sow - of group farrowing system already since 1935. In holding farms that were being created. this year Fritz HOFMANN had proposed using a In parallel with this development, the timed cover and farrowing system to control the beginning and the comprehensive introduction of breeding dates of a herd of sows in such a way artificial insemination of sows was used in that winter -related seasonal effects on the state of practicals farms more and more (KÖNIG and health of Pomeranian and East Prussian sow TSCHINKEL, 1966; SCHLEGEL, 1969). herds are avoided with the help of the production Activities were necessary now in the larger farms, process. This system was perfected in the late which made group -farrowing more accurate in 1950s after HOFMANN was appointed Professor time and more accurate in time. In this time these and Director of the Animal Breeding Institute at developments were significantly facilitated by the the University Jena. Under his leadership, a very availability of first control substances for the creative working group at this institute undertook stimulation or blocking of endocrine activities in the preparatory phase for the application of the ovary cycle of the female animal. Numerous sophisticated, periodic farrowing systems and the results from the basics and applied research in " German and international literature had been

13 RESEARCH IN PIG BREEDING, 14, 2020 (2) published (for example Mc CANN et al., 1960; • The separation of all sows in a stock in DZIUK and GEHLBACH, 1966; KARG, 1968; different groups with the same age and SMIDT, 1969; NISWENDER et al., 1970; production stages interrupts chains of MATSUO et al., 1971; CERNE and infection. It reduces or delays the course of SCHILLING, 1972). At that time, the essential infection. scientific foundations for biotechnologically • All production gets a long -term visibility assisted reproductive control processes in sows, with high transparency, ensuring good, safe especially cycle synchronization, were laid. The planning and health control in the animal idea of HOFMANN from the year 1935 for the groups. periodic farrowing system according to the "all -in • The group farrowing system allows a well - -everything -out principle" with permanently organized birth control by humans. It allows integrated service periods for the stable a litter compensation (cross forstering) in compartments was perfected and refined in this the relevant sow group, which is geared to way. Today, the periodic farrowing system is the animal health and zootechnical aspects, so most important part of responsible, health and that suckling piglet losses are minimized. performance -based sow husbandry and piglet • Biotechnical partus induction in the sows, production. Far -reaching advantages, which are which should be partially carried out in the aimed primarily at the health of the stock, are context of group farrowing, helps to reduce combined with it and make this form of very long gestation times, reduce the production organization for sow stocks essential: proportion of dead or weakly born piglets Organization of All in – all out system for the and reduces the occurrence of puerperal management of the barn units, in particular the diseases (MMA) in the sows. farrowing pen. This includes regular service For the organization and securing of group periods with firmly integrated cleaning and farrowing systems a control of reproduction in the disinfection after each production period in the sows is necessary. Their goal is to make the sows barn, when the animals occupate the barn. In the of a group nearly simultaneous with one another, pig with its short production periods, disruption so that all the sows in one of these groups can be of pathogen chains is of paramount importance in inseminated within a narrow time window. order to effectively counteract pathogen Simultaneous dates for insemination cause limited hospitalization. farrowing dates in all these animals to an average • The work in the respective stable of 115 gestation days. This is wanted and useful compartments takes place with uniform compared with the first mentioned advantages of groups of animals. It means the animal a group farrowing system. groups are balanced by age, developmental Reproduction control in sows is relatively and reproductive status. In the care of such easy to handle. The decisive advantage of this groups, there are demonstrably positive species is that sows in the puerperium and in the specialization effects among the colleagues lactation phase usually do not develop any heat active here. symptoms, they are in a lactation anestrus. The • In the pig with its short production periods, endogenous release of GnRH in the hypothalamus disruption of pathogen chains is important is blocked by the high, endogenous prolactin level in order to effectively counteract pathogen during this time and, as a result, follicle hospitalism. maturation is suppressed. The level is at • The subdivision of the total sow population the base level. Only with the weaning of the of the farm into smaller groups of sows suckling pig, it means with the removal of the provides the conditions for a homogeneous suckling stimulus the sow comes in heat again. immunity in the groups. This in turn allows There is a resumption of the ovarian cycle a high maternal immunity and low activity. The prolactin level drops rapidly, which excitation density. stops the blockade. The now 14 RESEARCH IN PIG BREEDING, 14, 2020 (2) increasing level of FSH and later of LH stimulates endocrinologically for the respective events such follicular growth and the concomitant estrogen as follicle growth and maturation, ovulations, synthesis. The ovarian cycle begins again, the sow gestation period, relatively concentrated and thus gets the oestrus 4 to 8 days after weaning from its to run according to the biology temporally piglets. limited, the use of hormones offers in the respective cycle phases. This happens as part of Control of Reproduction with time for weaning biotechnical measures for reproductive control of The main instrument for reproductive gilts and sows. The goal is generally solely the control in a stock of sows farmed on the group support of the already running endocrine farrowing system is the date of simultaneous processes in animals for the purpose of a safe and weaning of sows from their piglets at the end of timely occurrence of reproductive events. Such lactation. This moment is the decisive prelude to reproductive control is principally based on the the re -entry of estrus in all sows in this group. The interaction of stimulation and blockade of date for weaning creates the crucial prerequisite endocrine events. The principle of any hormone for a temporary insemination of all remote sows treatments is: "as much as necessary, as little as and thus for the group farrowing system. possible". This makes it clear that it is not the aim This group farrowing system has been used of biotechnical treatments to increase the number in larger stocks of sows for about 50 years, it of piglets per litter by higher ovulation rates and means it is applied for nearly 18 sow generations. to squeeze biological -physiological processes in During this very long time, sows whose the animal in a pattern that alone the work individual processes in the endogenous organization, the labor savings or relief and thus reproduction processes deviated greatly from the only economic aspects serves. The currently sow physiological average fell or fell out of the lines with very high reproduction potential reproductive process, it means out of the herd. It require no further performance increase. thus always had a very massive selection Obligatory conditions for the application of pressure, so that in comparison to previous any biotechnical measures are the optimal generations today sow groups thereby gradually environmental conditions (management), the with conditionally, temporally much more health of the sows, the normal, physiological uniform shape their reproductive processes and development of the animals with puberty and behavioral patterns. Undoubtedly, this contributed cycle activity with appropriate breeding to the ease of reproductive control in the sows of condition. There are no hormones or drugs to a group. cover management problems. This may not be the Additional zootechnical measures, which goal of reproductive control measures in sows. specifically include factors of posture, feeding, When hormones are used, active ingredients hygiene and management, have a supporting are used which correspond to the body's own effect on this effect. This zootechnical effect is hormones and thus have the same effect as these. based on the stimulating effect of the different Depending on the amount present, the hormones dosage or intensity of the successive stimulus promote or inhibit each other. This change factors, but also on the sequence of different key mechanism represents already principle of the stimuli, such as tactile (body contact), acoustic regulation of the sex hormones. Sex hormones act (lute), visual (eye contact) and olfactory (odor) regulate, but can never initiate a process stimuli. regardless of the reaction situation of the Biotechnical treatments for control of organism. This principle is subject to any reproduction biotechnical treatment of sows for reproductive In order to allow the reproduction processes control. Stimulatory effects are always directed to in all sows of a group in the respective the subordinate levels of the hypothalamic - pituitary -gonadal system. Blockades, on the other

15 RESEARCH IN PIG BREEDING, 14, 2020 (2) hand, aim at the upstream, higher levels in the Synthesis site hypothalamus - target organ system. pituitary Exogenous agents with stimulating effect The gonadotropin -releasing hormone stimulate the secretion of the body's own (GnRH) formed in the hypothalamus acts as a hormones in the target organ or in the release hormone in the pituitary (pituitary downstream organs according to the hormonal anterior lobes - HVL), the secretion of the action cascade (hypothalamic → pituitary hormones, which act on the target organ, the → gonads) or support them. The naturally gonad (ovary). The GnRH is pulsatile delivered occurring reproductive processes are promoted in in a frequency of about 20 to 30 minutes. It this way. On the other hand, blocking substances triggers in the downstream organ, the pituitary cause a secretion stop in the respective higher gland, the secretion of LH and, to a lesser levels in the hypothalamic -pituitary -gonadal extent, FSH. GnRH is synthetically produced system. and used for ovulation stimulation in sows with Hormonal agents are used in piglet synchronization of etrus (synchronization of production to synchronize sexual cycles in gilts, ovulation with timed insemination). to support ovarian function in sows after weaning Since longer timer, a separate FSH releasing piglets, to stimulate ovulation in gilts and sows, factor has been suggested (Mc CANN et al., and to induce parturition. This is based on 1998). This factor corresponds to the lamprey scientifically based studies with an extremely GnRH -III (lGnRH -III) found in the lamprey high number of animals. (SOWER et al., 1993). Since autumn 2008, a For reproductive control in sows, natural synthetic GnRH preparation containing this and synthetically produced hormones are used. active substance has been available (ENGL, Natural hormone preparations are gonadotropins 2010). After luteal phase it leads to the growth obtained from serum -bearing mares (Equine of the follicles in sows and thus to stimulates chorionic gonadotrophin - eCG, also known as estrus (ENGL, 2010). PMSG - Pregnant serum genonadotrophin) and In general, the half -life of GnRH is from the urine of pregnant women (Human functionally very short. It is only 5 to 10 chorionic gonadotropin - hCG). minutes. This applies to all synthetically The synthetically produced hormones produced gonadotropin -releasing hormones. resemble or correspond in their structure to the There are no waiting period for edible tissue natural hormones. Often, natural hormones are after administration of GnRH preparations. very difficult to obtain. In addition, the use of Synthesis site pituitary anterior lobes - natural substances is not always risk -free. target organ gonads (ovary) Synthetic hormones with a clear biochemical The gonadotropic hormones FSH (follicle structure can be safely produced and usually have stimulating hormone) and LH (luteinizing a better effect, so much lower amounts must be hormone), which are produced by GnRH in the applied to achieve the same effect as natural pituitary anterior lobe (HVL), induce follicular hormones. In sows, synthetic hormones are used growth (FSH) and ovulation (LH) on the to stimulate follicular growth and ovulation ovaries. Both hormones are always related. (GnRH), to induce labor and to support For these hormones, natural extra -pituitary contractions (prostaglandins, oxytocins) and gonadotropins (eCG, hCG) are used for cycle synchronization in gilts (Altrenogest). reproductive control in sows. Natural and synthetically produced hormones, The eCG (synonym PMSG) is used in gilts after which are used for reproductive control in sows, drug cycle block and in remote sows for cycle are assigned to five categories or classes stimulation (cycle start), it means it will be used according to their secretion sites and directions of to stimulate follicular growth. It should be effects:

16 RESEARCH IN PIG BREEDING, 14, 2020 (2) noted that the eCG molecule combines two Synthetic oxytocin analogues with a endocrine modes, FSH and LH. prolonging effect (active substance carbetocin)

The natural hCG corresponds in its effect to show a change in the oxytocin molecule. The the endogenous LH. Both hormone preparations result is, there is an extension of the chemical - eCG and hCG have a very short half life of only a and metabolic stability. In the case of an equally few minutes due to their function. A waiting rapid onset of action, in comparison to the period for edible tissue is not specified. original oxytocin, a greatly prolonged duration Both eCG and hCG induce in the sows analogous of action on the rhythmic myometrial to their endogenous gonadotropins FSH and LH contractions of the uterus is achieved without - on the ovary in addition to morphological unphysiological reactions occurring. Depot - functional changes, the formation of so called oxytocin preparations, for example Depotocin® subordinate sex hormones (sex steroids) such as (VEYX Pharma GmbH) is used in the partial - estrogens (17 βÖstradiol) in the growing follicle partus induction after previous birth induction and progesterone in the corpus luteum. with a prostaglandin F2α dose for the purpose of - In addition to the natural exogeneous stimulating the birth processes. hypophysial gonadotropins, the synthetically In the case of pregnant sows, they also produced GnRH is increasingly being used. This stimulate labor, independently of the induction is the derivative of the natural gonadotropin of the partus. The half -life of such synthetic releasing hormone. It contains the active oxytocin analogs is 2 to 4 hours. There is no - - ingredient D Phe 6 LHRH. Thanks to its high waiting time for edible tissue and milk. efficacy, it is particularly suitable for ovulation In artificial insemination of the sows, initiation after previous cycle stimulation in a adding natural oxytocin to the inseminate may very low dosage. stimulate the myometrial contractions in the - Synthesis site pituitary backbone target uterus during insemination, which has a organ smooth muscle beneficial effect on the transport of sperm into

The release of the hormone formed and the ampoule to the place of fertilization. This stored in the posterior pituitary (HVL), oxytocin, promotes the absence of instrumental seed is usually initiated by mechanical stimuli (nipple transfer stimuli to the uterine epithelium and stimulation, piglet pressure during expulsion from myometrium, which become active during the birth path, penile pressure in the vagina natural mating by penis and ejaculate. during mating). It triggers contractions of smooth Sexual steroids (place of formation: ovary) muscle (myometrium) of the uterus and In Germany, only one steroidal active myoepithelia in the wall of the alveoli of the substance is approved for use in sow mammary gland (milk injection). Due to its short production, the "Altrenogest" (Allyl - half life of only 1 to 9 minutes, no waiting period Trenbolone), which contains the active is specified. substance in oily solution,. The producer of the Natural and synthetically produced oxytocin active ingredient is the company Roussel Uclaf preparations are used in the following indications (F). Other types of steroid such as estrogen, in sows: which are widely used in human medicine, are • - - Labor stimulation in case of labor not used in sows for piglet production.

weakness Sexual steroids with this drug are • Stimulation of milk injection, predominantly administered orally only to gilts • Stimulation of the birth processes after as a cycle blocker for oestrus synchronization. previous birth induction with a This synthetically produced progestagens

prostaglandin F2α dose, corresponds in its effect to endogenous • Promotion of postpartum uterine involution.

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mechanism (bloodstream), Altrenogest blocks duration of pregnancy has been reached. This the further secretion of gonadotropins (FSH, affects only about 50% of the sows. LH) in the pituitary gland. The growth of The waiting time for edible tissue after ovarian follicles is thus inhibited. It can only be PGF2α treatment is 2 days. In Germany, about up to the size reached in the diestrus. The ovary 50% of the sow herds of any herd size are cycle is blocked with it. During the 18 -day subjected to birth synchronization with partial medication with a daily dose of 20 mg per partus synchronization. animal of the active ingredient altrenogest takes place in the animals, the luteal body regression. Hormone use in sows and possible At the end of the maximally 18 -day environmental pollution administration of the , the corpora In sows, no estrogens are used in high long - lutea have regressed in all gilts so treated. The term doses. Only low -dose glycoproteins, new cycle starts uniformly in all sows. gonadotropins and biological or synthetic release As a steroidal substance, Altrenogest has a factors from the interbrain are used. longer half -life than the hormones produced in In general, in animals, the metabolites of the the hypothalamus and pituitary (GnRH, FSH, body's own and exogenous hormones on LH). The waiting time for edible tissue is set at excretions in the environment. 9 days. Most substance classes used in sows have a Tissue hormon prostaglandin (PGF2α) very short duration of effect and therefore also As further endogenous hormones in piglet very short half -lives, which does not result in production the prostaglandins are important, waiting times for edible tissue. Therefore, no especially those of the type PGF2α. These are significant environmental impact is expected from derivatives of fatty acids with multiple these substances. In addition, the absolute functions in the field of reproduction. The amounts and concentrations of the hormonal natural prostaglandin F2α is synthesized in the degradation products are extremely low. This uterine mucosa and in the placenta. In cyclical deviates only with the steriodal Progestagen sows, it triggers luteolysis during the ovary "Altrenogest". Progestagen "Altrenogest" has cycle after the 12th day of the cycle. At the end been in use since the beginning of the 90s. During of gestation, PGF2α is increasingly produced in the 18 -day medication, the gilts excrete the the placenta, causing luteolysis and thus resulting degradation products with the urine. It initiating the end of the progesterone phase. should be noted, however, that this is a progestin The birth begins after that. and not estrogen -like substances. Like the In addition, the PGF2α, with the participation estrogens, progestagens do not belong to the of oxytocin, stimulates the recurrent, rhythmic group of "endocrine disruptors" that are known to uterine contractions and thus supports the have carcinogenic and mutagenic effects. contractions and expulsion of the fruits. The synthetically produced PGF2α fulfills Scope of application of hormonal treatments of these same functions. In the sow husbandry it is sows used in the context of the synchronization of According to estimates of the Federal parturition in sows of a group which are Chamber of Veterinarians today 10 to 15% of inseminated in the same time. sows are treated hormonally. That's between Birth synchronization in a group of sows 205,000 and 307,000 animals a year in Germany. is characterized by partial birth induction. This Of all the gilts only about 30% get a biotechnical means that only those sows receive a birth treatment for cycle synchronization. induction with Cloprostenol (PGF2α), which Large farms that manage their sowing stock have not yet terminated when the average

18 RESEARCH IN PIG BREEDING, 14, 2020 (2) necessary to perform an additional heat ENGL, S. (2010): Neue Ergebnisse nach einer synchronization of the gilts, if in general every Zyklusstimulation mit Peforelin bei Sauen. week an insemination period with the deposed Proc. 16. Mitteldeutscher Schweine - old sows is due. The brittle gilts can easily be Workshop in Bernburg, Tag. -band 95 -106 assigned to the respective old sow group and thus KARG, H. (1968): Endokrine Regelkreise der incorporated into the company group farrowing Fortpflanzung und deren willkürliche system. In addition, the use of biotechnics in Steuerung. – Tierzucht, Züchtungsbiologie, Germany has declined in recent years because 84, 262 predominantly the large farms, which are mostly KÖNIG, I. (HRSG., 1982): Fortpflanzung bei located in East Germany and often work with Schweinen. VEB Deutscher foreign sow genetics, do not use biotechnical Landwirtschaftsverlag, Berlin, 126 -129 treatments and consequently no hormones. These KÖNIG, I., TSCHINKEL, INGEBORG (1966): include very fertile sows of various breeding Untersuchungen zur Organisationsform der companies, which are used as sows for mother Schweinebesamung . – Sonderband d. wiss. lines. Zeitschr. der Friedrich -Schiller -Universität Sow stocks that are managed in a two -week Jena, 137 - 148 or three -week rhythme and that supplement their MATSUO, H., BABA, Y., NAIR, R. M. G., stock with the purchase of a few, but larger ARIMURA, A., SCHALLY, A. V. (1971): groups of gilts from the higher breeding level - Structure of the porcine LH - and FSH - stage, often rely heavily on the application of releasing hormone. 1. The proposed amino biotechnical gynecological synchronization aids acid sequence. – Biochem. Biophys. RS to the needed gilts for remontation in the Commun. 43, 1334 respective insemination group of the weaned Mc CANN, S. M., YALEISNIK, S., sows in smaller numbers easily integrate. FRIEDMANN, H. M. (1960): LH -releasing In general, it should be noted that the use of activity in hypothalamic extracts. – Proc. biotechnical drugs in sow husbandry optimizes Soc. Exp. Biol. Med. 104, 432 work processes and makes animal movements Mc CANN, S.M., KIMURA, M., more controllable. For animal health, for example WALCZEWSKA, A., KARANTH, S., through controlled animal contact and better RETTORI, V., YU, W.H. (1998): cleaning and disinfection, and for well -being Hypothalamic control of FSH and LH by through optimized animal observation in groups, FSH -RF, LHRH, cytokines, leptin and nitric each with the same reproduction phase, this oxide. - Neuroimmunomodulation 5, 193 - undoubtedly has a positive effect. As a result, 202 above all antibiotics should be saved, whose NISWENDER, G. D., REICHERT, J. L. E.; application and documentation have been newly ZIMMERMANN, O. R. (1970): regulated by the legislator in the sense of a lower Radioimmunoassay of serum levels of burden on animals and humans. throughout the estrous cycle in pigs. – Endocrinology 87, 576 References SCHLEGEL, W. (1969): Untersuchungen zur CERNE F., SCHILLING, E. (1972): Induktion Fortpflanzungsleistung weiblicher Schweine synchroner Rauschen und Ovulationen beim unter besonderer Berücksichtigung Schwein. – VII Intern. Congr. On Animal zootechnischer und physiologischer Reprod. and Artificial Insemination, Einflussfaktoren – ein Beitrag zur effektiven München, 1039 Nutzung der künstlichen Besamung beim DZIUK, P. J.; GEHLBACH, G., D. (1966): Schwein. – Habil. - Schr. Univ. Jena Induction of ovulation and fertilization in the immature gilt. – J. Anim. Sci., 25, 410

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SMIDT, D. (1969): Endogene und exogene Einflüsse auf Ovarialfunktionen und embryonale Entwicklung. Arch. Gyn. 207 , 155. SOWER, S.A., CHIANG, Y., LOVAS, S., CONLON, J.M. (1993): Primary structure and biological activity of a third gonadotrophin - releasing hormone from lamprey brain. – Endocrinology 60, 1125 -1131

Corresponding Address: Prof. Dr. Martin Wähner Anhalt University of Applied Sciences Dep. Agriculture and Land Management Strenzfelder Allee 28 06406 Bernburg, Germany E-mail: Martin.Waehner@hs -anhalt.de

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