Amino Acids) Metabolism in Weanling Piglets

Received: 21 June 2019 | Revised: 3 October 2019 | Accepted: 10 October 2019 DOI: 10.1111/asj.13311

ORIGINAL ARTICLE

Effects of rice feeding on growth performance and protein (amino acids) metabolism in weanling piglets

Yusuke Tasaka | Kanako Tachihara | Ryutaro Kagawa | Ryozo Takada

Graduate School of Science and Technology, Niigata University, Niigata City, Abstract Niigata, Japan We investigated the effects of rice feeding on growth performance and protein

Correspondence (amino acids) metabolism of weanling piglets. In all, 16 weanling piglets with an aver‐ Ryozo Takada, Graduate School of Science age initial weight of 7.5 kg were divided into two groups. One group was fed a corn‐ and Technology, Niigata University, 8050 Igarashi 2 no‐cyo, Nishi‐ku, Niigata City, soybean meal‐based diet, and the other was fed a rice‐soybean meal diet, containing Niigata 950‐2181, Japan. around 46% of corn or rice, respectively. A two‐week growth trial was conducted. Email: [email protected] The average daily gain (p = .025) and feed efficiency (p = .011) in rice‐fed piglets were Present addresses significantly higher than those in corn‐fed piglets. Liver lysine‐ketoglutarate reduc‐ Kanako Tachihara, Nissan Chemical Corporation, Tokyo, Japan tase activity tended to be lower (p = .073) in rice‐fed piglets than in corn‐fed piglets. Plasma urea nitrogen concentration in rice‐fed piglets was significantly lower than Ryutaro Kagawa, Maruha Nichiro Corporation, Tokyo, Japan that in corn‐fed piglets. Plasma glucose and insulin concentrations were significantly higher in rice‐fed piglets than in corn‐fed piglets. Plasma‐free valine, isoleucine, and Funding information Grant‐in‐Aid for Research and Development tryptophan concentrations were significantly higher in rice‐fed piglets than in corn‐ Project from the Ministry of Agriculture, fed piglets. In contrast, plasma histidine concentration was significantly lower in Forestry and Fisheries, Japan; Research Grant Project by Ito Foundation rice‐fed piglets than in corn‐fed piglets. Overall, these results show that rice feeding improves the growth performance and affects the protein (amino acids) metabolism in weanling piglets.

KEYWORDS growth performance, piglets, protein metabolism, rice feeding

1 | INTRODUCTION Serrano, Valencia, & Mateos, 2010; Vicente, Valencia, Serrano, Lazaro, & Mateos, 2008, 2009; Yagami & Takada, 2017) and reduces In general, weanling piglets undergo various stresses, such as the occurrences of diarrhea (Pluske, Black, Pethick, Mullan, & Hampson, sudden change of diet from milk to a cereal‐based diet and sepa‐ 2003; Pluske et al., 1996) in weanling piglets. Similar improvement ration from their mother and removal to a new pen environment, of growth performance has also been reported in chicks (Ebling resulting in a lower feed intake, retardation of growth, and inci‐ et al., 2015; Fujimoto, Fujita, & Takada, 2018; Gonzalez‐Alvarade, dences of diarrhea. Thus, reducing stress is considered to improve Jimenez‐Moreno, Lazaro, & Mateos, 2007; Jimenez‐Moreno, the growth performance in weanling piglets and is valuable in pig Gonzalez‐Alvarado, Lazaro, & Mateos, 2009). In our previous report production. (Yagami & Takada, 2017), plasma urea nitrogen (PUN) in rice‐fed Rice is one of the main cereals in the world, especially in piglets was significantly lower than that in corn‐fed piglets, sug‐ Southeast Asia. In Japan, however, rice is not used for domestic gesting that rice feeding might reduce the protein and amino acids animal feed because of its high cost. Nevertheless, recently, much degradation. Furthermore, higher feed intake in rice‐fed piglets attention has been focused on rice feeding, as it improves growth was observed, suggesting that lysine and some other amino acids performance (Mateos, Lopez, Latorre, Vicent, & Lazaro, 2007; in the diets were slightly deficient. In general, if a diet composes Mateos, Martin, Latorre, Vicente, & Lazaro, 2006; Parera, Lazaro, slightly insufficient amino acids, a feed intake increases (Takada &

Mori, 1988). Therefore, this experiment was conducted to clarify at June and October in 2017. Piglets were weaned at 21–23 days of the mechanism of rice feeding on growth performance and protein age and transferred from a nearby pig farm to Niigata University. (amino acids) metabolism in weanling piglets using a higher amino They were housed individually in cages (1.3 m × 0.6 m) with an elec‐ acids diet compared to our previous report. tric heater and given free access to feed and water. Ambient temper‐ ature in the cages was around 24°C–28°C. After a 5‐day adaptation period, a total of 16 piglets from the four litters were divided into 2 | MATERIALS AND METHODS two dietary groups. One group, containing eight piglets, that is, lit‐ termates from four litters, was used as the control group and fed All animal experiments were conducted in compliance with the pro‐ a corn‐based feed; the other, that is, the experimental group, also tocol reviewed by the Institutional Animal Care and Use Committee containing eight piglets, was fed a rice‐based feed. The rice used was and approved by the President of Niigata University (Permit Number: brown Niigatajiroh rice, and it was ground to pass through a 2‐mm Niigata Univ. Res.28‐76‐2). mesh filter. The composition of the control and experimental diets is shown in Table 1. Amino acids contents in each diet is shown in Table 2. Each diet contained around 47% corn or rice and was for‐ 2.1 | Animals, diets, and experimental design mulated to meet the nutrient requirement of weighing 5–10 kg in A total of 16 crossbred male piglets ((Landrace × Large White) × Duroc) Japanese Feeding Standard for Swine (NARO, 2013). All the piglets littermates from four litters were used. Growth trials were conducted were fed twice a day at 09.00 and 16.00 hr. During the two‐week growth trial, body weight was recorded weekly and feed intake was measured daily. TABLE 1 Composition of experimental diets (g/kg)

Item Corn Rice 2.2 | Sample collection Ingredients During the final 3 days of the experiment, some feces were col‐ Corn 466.9 – lected to determine the dry matter (DM) and crude protein (CP) Brown rice – 460.9 digestibility. Collected feces were frozen (−20°C) immediately and Soybean meal 150 150 stored until further analysis. On the final day of the experiment, Soybean meal (extruded) 80 90 body weight and feed intake were recorded. Three hours after feed Dried skim milk 200 200 removal, 50 g of each diet was re‐fed, and 1 hr after the re‐feed‐ Soybean oil 60 55 ing, blood samples were collected by jugular venipuncture in hep‐ Dicalcium phosphate 15 15 arinized polyethylene tubes and kept on ice until centrifugation Calcium carbonate 6 6 (2000 × g for 10 min) at 4°C to recover the plasma. The plasma Sodium chloride 5 5 obtained was stored at −30°C for the analysis of concentrations L‐lysine HCl 3 3.5 of PUN, glucose, insulin, and free amino acids. The piglets were DL‐methionine 2.5 2.5 electrically stunned and euthanized by exsanguination. Then, the L‐threonine 2 2.5 liver was immediately removed and stored at −80°C until analysis L‐tryptophan 0.1 0.1 of LKR activity. Vitamin mixturea 4.5 4.5 Mineral mixtureb 2 2 TABLE 2 Essential amino acids composition in experimental diet c Antibiotics 2 2 Corn Rice Chromic oxide 1 1 (g/kg) Calculated chemical composition Threonine 10.4 10.9 ME (MJ/kg) 15.1 15.1 Valine 10.5 10.8 CP (g/kg) 211 215 Methionine + Cystine* 9.2 9.7 Calcuium (g/kg) 90 90 Isoleucine 9.0 9.3 Phosphorus (g/kg) 70 73 Leucine 19.1 17.8 a Provided the following (per kg of diet): retinol, 6 mg; cholecalciferol, Phenylalanine + Tyrosine 17.8 18.4 100 μg; αtochopherol acetate, 200 mg; thiamine mononitrate, 2.5 mg; Histidine 5.6 5.6 riboflavin, 17.5 mg; pyridoxine HCl, 1.25 mg; D‐Ca pantothenate, 272.5 mg; nicotinamide, 15 mg; choline chloride, 1,440 mg. Lysine 15.5 16.3 b Provided the following (per kg of diet); Mn, 100 mg; Fe, 100 mg; Cu, Arginine 11.4 12.8 20mg; ZnCO , 120 mg; CaI , 2 mg. 3 2 Tryptophan* 2.7 2.9 cProvided the following (per kg of diet); avilamycin, 20 mg titer; colistin sulfate, 20 mg titer; morantel citrate, 30 mg titer. *Calculated value. TASAKA et al. | 3

were significantly higher in rice‐fed piglets than in corn‐fed piglets after 2.3 | Determination of DM and CP digestibility 0–2 weeks. However, there was no significant difference in ADFI be‐ DM and CP digestibility in each diet were determined using a chromic tween corn‐ and rice‐fed piglets. As a result, FE was significantly higher oxide indicator method, with each diet containing 0.1% of chromic in rice‐fed piglets than in corn‐fed piglets after 0–2 weeks. oxide. Precisely, the methods were followed as described previously (Yagami & Takada, 2017). 3.2 | Digestibility

Dry matter (DM) and crude protein (CP) digestibility are shown in 2.4 | Assay Table 4. Significant differences in digestibility of DM and CP be‐ tween corn‐ and rice‐fed piglets were not observed. 2.4.1 | Plasma urea nitrogen (PUN), glucose, and insulin concentrations 3.3 | Plasma constituents PUN was measured by the diacetyl monoxime method (Matsumoto, 1981). Plasma glucose concentration was measured with a commer‐ Plasma urea nitrogen (PUN), glucose, and insulin concentrations are cial kit (Glucose C‐II‐test Wako). Plasma insulin concentration was also shown in Table 5. PUN was significantly lower in rice‐fed piglets than determined using a commercial kit (Mercodia Porcine Insulin ELISA). TABLE 3 Growth performance of piglets fed a diet with corn or rice 2.4.2 | Liver lysine‐ketoglutarate reductase (LKR) activity Corn Rice p value Initial body 7.4 ± 0.2 7.6 ± 0.2 .498 The LKR activity was determined by the method described by weight (kg) Noda and Ichihara (1978). The liver was thawed and homoge‐ Average daily gain (g/d) nized in 10 mmol/L potassium phosphate buffer (pH 7.6) contain‐ 0–1 week 188 ± 18 236 ± 25 .135 ing 0.1 mmol/L EDTA, 5 mmol/L 2‐mercaptoethanol, and 0.1% 1–2 week 439 ± 21 529 ± 39 .061 TritonX‐100 in a Polytron homogenizer to produce a 10% homogen‐ ate. The homogenate was centrifuged at 23,000 × g for 30 min. The 0–2 week 313 ± 17 382 ± 21 .025 supernatant obtained was used for the assay of LKR activity. Average feed intake (g/d) 0–1 week 257 ± 23 270 ± 24 .703 1–2 week 561 ± 27 600 ± 28 .345 2.4.3 | Amino acids composition in experimental 0–2 week 409 ± 23 435 ± 25 .461 diet and plasma‐free amino acids concentration Feed efficiency (gain/feed) Diet was hydrolyzed in 6 mol/L hydrochloric acid solution at 110°C for 0‐1 week 0.729 ± 0.043 0.870 ± 0.057 .068 24 hr. After neutralization by adding 5 mol/L sodium hydroxide, the 1‐2 week 0.789 ± 0.039 0.879 ± 0.046 .159 suspension was diluted with water, and 1 ml of the supernatant was 0‐2 week 0.770 ± 0.032 0.881 ± 0.020 .011 filtered through a 0.45 μm membrane and used for the determination Note: Values are means ± SE (n = 8). of amino acids using an HPLC system (Shimazu). Plasma was prepared for free amino acid analysis by adding equal volumes of plasma and TABLE 4 Dry matter and crude protein digestibility in the 6% sulfosalicylic acid and centrifuging at 10,000 × g for 20 min. The experimental diets resulting supernatant was used for the determination of amino acids. Corn Rice p value

Dry matter, % 87.5 ± 1.0 88.1 ± 2.1 .451 2.5 | Statistical analysis Crude protein, % 85.5 ± 2.3 84.0 ± 3.9 .377 Statistically significant differences between two treatment groups Note: Values are means ± SE (n = 8). were assessed with a t test, using the Excel Statistic. The results are presented as means and standard errors. A p value of <.05 was con‐ TABLE 5 Plasma urea nitrogen, glucose, and insulin sidered significant. concentrations in piglets fed a diet with corn or rice

Corn Rice p‐value

3 | RESULTS Plasma urea ni‐ 9.57 ± 1.75 5.28 ± 1.40 .033 trogen (mg/dL) 3.1 | Growth performance Glucose (mg/dL) 106 ± 3 119 ± 3 .013

The results of average daily gain (ADG), average daily feed intake (ADFI), Insulin (μg/L) 0.110 ± 0.006 0.148 ± 0.015 .035 and feed efficiency (gain/feed, FE) are shown in Table 3. ADG and FE Note: Values are means ± SE (n = 8). 4 | TASAKA et al.

TABLE 6 Liver lysine‐ketoglutarate reductase (LKR) activity in TABLE 7 Plasma‐free amino acids concentrations in piglets fed a piglets fed a diet with corn or rice diet with corn or rice

Corn Rice p value Corn Rice p value

LKR activity, μmole/ 1.17 ± 0.072 0.95 ± 0.082 .073 Essential amino acids, μmol/L min/g liver Threonine 593 ± 178 691 ± 271 .406 Note: Values are means ± SE (n = 8). Valine 257 ± 45 328 ± 41 .005 in corn‐fed piglets. Plasma glucose and insulin concentrations were Methionine 129 ± 30 132 ± 26 .845 significantly higher in rice‐fed piglets than in corn‐fed piglets. Isoleucine 155 ± 25 270 ± 30 .002 Leucine 220 ± 43 195 ± 39 .236 Phenylalanine 98 ± 12 80 ± 23 .075 3.4 | LKR activity Histidine 80 ± 14 62 ± 11 .011 The results of liver LKR activity are shown in Table 6. LKR activity Lysine 182 ± 71 221 ± 92 .362 in rice‐fed piglets tended to be lower (p = .073) than that in corn‐fed Arginine 172 ± 78 173 ± 91 .983 piglets. Tryptophan 67 ± 14 89 ± 23 .035

Nonessential amino acids, μmol/L 3.5 | Plasma‐free amino acids Aspartic acid 31 ± 5 29 ± 5 .447 Serine 239 ± 82 229 ± 5 .773 Plasma‐free amino acids concentrations are shown in Table 7. Glutamic acid 200 ± 79 206 ± 53 .872 Plasma‐free valine, isoleucine, tryptophan, and glycine concentra‐ tions were significantly higher in rice‐fed piglets than in corn‐fed Glycine 899 ± 205 1,103 ± 160 .043 piglets. In contrast, free histidine concentration was lower in rice‐fed Alanine 570 ± 126 664 ± 115 .143 piglets than in corn‐fed piglets. Tyrosine 161 ± 27 164 ± 47 .861 Note: Values are means ± SE (n = 8).

4 | DISCUSSION day and 12.4 g lysine/kg diet, respectively. The diet in our previous report might be slightly deficient in lysine. The results of this study showed that ADG and FE were significantly PUN in rice‐fed piglets was significantly lower than that in higher in rice‐fed piglets than in corn‐fed piglets. This report is, to corn‐fed piglets (Table 5). This concurs with our previous re‐ our knowledge, for the first to show higher FE in rice‐fed piglets port. PUN is well known as a good indicator of protein retention than in corn‐fed piglets. In our previous report (Yagami & Takada, (Mitchel, Becker, Jensen, Harmon, & Norton, 1968). Thus, the 2017), the FE between corn‐ and rice‐fed piglets was not different, lower PUN in rice‐fed piglets suggests higher protein accumula‐ although ADG and ADFI were significantly higher in rice‐fed pig‐ tion, resulting in higher ADG. Higher plasma concentrations of in‐ lets than in corn‐fed piglets. The clear difference in FE and ADFI sulin were observed in the rice‐fed piglets (Table 5); it is possible between our previous report and this report could partially be ex‐ that the higher level of insulin caused higher protein synthesis or plained by the difference in total lysine content in the diets. Lysine lower protein degradation, or both, compared with corn‐fed pig‐ content in the diets of this experiment was 15.5–16.3 g/kg, which lets, leading to higher protein retention in rice‐fed piglets. Tester, satisfy the NRC feeding standard (NRC, 2012); however, in our Karkaras, and Qi (2004) reported that the size of rice starch gran‐ previous report (Yagami & Takada, 2017), lysine content was 12.9– ules was 3–8 μm, while that of cornstarch granules was 2–30 μm. 13.0 g/kg, which satisfied the Japanese feeding standard. Expected Yin, Zhang, Huang, and Yin (2010) indicated that rice starch was weight gain in Japanese feeding standard is 250 g/day, which is hydrolyzed more quickly than cornstarch using in vitro and in vivo lower than the ADG (468 g/day) observed in our previous report. experiments. Furthermore, the glycemic index of rice was higher The expected ADG of 250 g/day of the Japanese feeding standard is than that of corn (Sora‐Oriol, Roura, & Torrallardona, 2014). These probably too low. Thus, ADFI in rice‐fed piglets might be increased results well support the higher plasma insulin and glucose con‐ to maintain a higher lysine intake, leading to higher weight gain. As centrations observed in this study. However, it is well known that a result, similar FE between rice and corn‐fed piglets was observed. plasma insulin concentration is affected by the sampling condition. In contrast, in this experiment, rice‐fed piglets might not need to Menoyo et al. (2011) reported that the plasma insulin level be‐ increase the ADFI. The diet was sufficient in lysine to maintain ADG tween rice‐ and corn‐fed piglets showed no significant difference. (382 g/day), resulting in a significantly higher FE in rice‐fed piglets They collected plasma under conditions of ad libitum feeding. In than in corn‐fed piglets. Expected weight gain and lysine concentra‐ our experiment, however, plasma was collected 1 hr after re‐feed‐ tion in the NRC‐recommended diet (7–11 kg body weight, 2012) are ing of a 50‐g diet after a previous 3 hr of fasting. In general, pigs 335 g/day and 15.3 g lysine/kg diet, respectively, whereas those of are raised under ad libitum feeding in commercial conditions, thus, the Japanese feeding standard (5–10 kg body weight, 2013) is 250 g/ plasma insulin response under ad libitum feeding will need to be TASAKA et al. | 5 evaluated to understand the relevance between rice feeding and Fujimoto, M., Fujita, N., & Takada, R. (2018). Effects of a rice diet insulin action. and phytase addition on growth performance, tissue weights, phosphorus and nitrogen retention, and on liver threonine de‐ LKR is a rate‐limiting enzyme of lysine degradation, and lysine hydrogenase, malic enzyme and fatty acid synthase activities in is one of important essential amino acids in pig nutrition. Because a broiler chicks. Animal Science Journal, 89, 770–776. https://doi. large amount of lysine is required for maximum growth (NRC, 2012) org/10.1111/asj.12991 compared with the other essential amino acids, lysine is considered Gonzalez‐Alvarade, J. M., Jimenez‐Moreno, E., Lazaro, R., & Mateos, G. G. (2007). Effect of type of cereal, heat processing of the cereal, and the first limiting amino acid in diets based on plant feedstuffs. In inclusion of fiber in the diet on productive performance and digestive this experiment, liver LKR activity tended to be lower (p = .073) in trial of broilers. 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