Regulation of taste-active components of meat by dietary leucine

1. Regulation of meat taste is one effective method for improvement of meat quality. In this study, effects of dietary leucine (Leu) content on taste-active components, especially free glutamate (Glu), in meat were investigated. 2. Broiler chickens (28 d old) were fed on diets with graded dietary Leu content (100, 130 or 150% of Leu requirement in NRC, 1994) for 10 d before marketing. Taste-active components of meat (free amino acids and ATP metabolites) and sensory score of meat soup were estimated. 3. Free Glu content, the main taste-active component of meat, was significantly increased by dietary Leu. Compared with the Leu 130% group, free Glu was increased by 17% in the Leu 100% group. Free Glu of meat tended to decrease in the Leu 150% group. In contrast, inosine monophosphate content in meat did not change among all groups. 4. Sensory evaluation of meat soup from the Leu 100 and 150% groups showed that they had different meat tastes. Sensory scores of overall preference, umami taste and chicken-like taste were significantly higher in the Leu 100% group. 5. These results suggest that dietary Leu content is a regulating factor of free Glu in meat. Decreasing dietary Leu induces an increase in the free Glu content of meat and improves meat taste.     

The effects of branched-chain amino acids on sow and litter performance

Sows (n = 306; PIC, Line C-19; average parity 2.1) were used to evaluate the interrelationship between valine, isoleucine, and leucine on sow and litter performance. Our objective was to determine whether the increase in litter weaning weight associated with added dietary valine is specific for valine or a result of the total branched-chain amino acid (i.e., isoleucine and[or] leucine) concentration of the diet. Eight dietary treatments (36 to 41 sows/treatment) were arranged as a 2 x 2 x 2 factorial with two levels of valine (.80 and 1.20%), isoleucine (.68 and 1.08%), and leucine (1.57 and 1.97%). This provided total branched-chain amino acid levels of 3.05, 3.45, 3.85, and 4.25%. The lowest level of each branched-chain amino acid was similar to that in a .90% lysine corn-soybean meal diet containing .15% L-lysine HCl. Amino acids other than valine, isoleucine, and leucine met or exceeded their suggested estimates relative to lysine using ratios derived from the National and Agricultural Research Councils. Average number of pigs on d 2 of lactation was 11.2, and average lactation length was 20.9 d. Number of pigs weaned (x = 10.6), sow ADFI (x = 5.85 kg), and sow weight loss (x = 4.25 kg) were not affected by dietary treatment (P > .10). Sow backfat loss (P < .02), litter weaning weight (P < .04), and litter weight gain from d 2 to weaning (P > .05) increased as dietary valine increased. Litter weight at weaning and litter weight gain were not affected by dietary isoleucine (P > .80) or leucine (P > .60). Sixteen or 17 sows per treatment (129 total) were milked manually on d 14 to 16 of lactation. Increasing dietary valine tended to increase milk urea N (P < .07) but did not affect milk DM, CP, fat, lactose, or ash. Increasing dietary isoleucine or leucine had no effects on milk composition. These results confirm the importance of dietary valine for increased litter weaning weight, independent of either additional dietary leucine or isoleucine.     

Regulation of intestinal health by branched‐chain amino acids

Besides its primary role in the digestion and absorption of nutrients, the intestine also interacts with a complex external milieu, and is the first defense line against noxious pathogens and antigens. Dysfunction of the intestinal barrier is associated with enhanced intestinal permeability and development of various gastrointestinal diseases. The branched‐chain amino acids (BCAAs) are important nutrients, which are the essential substrates for protein biosynthesis. Recently, emerging evidence showed that BCAAs are involved in maintaining intestinal barrier function. It has been reported that dietary supplementation with BCAAs promotes intestinal development, enhances enterocyte proliferation, increases intestinal absorption of amino acids (AA) and glucose, and improves the immune defenses of piglets. The underlying mechanism of these effects is mediated by regulating expression of genes and proteins associate with various signaling pathways. In addition, BCAAs promote the production of beneficial bacteria in the intestine of mice. Compelling evidence supports the notion that BCAAs play important roles in both nutrition and intestinal health. Therefore, as functional amino acids with various physiological effects, BCAAs hold key roles in promoting intestinal development and health in animals and humans.     

母猪日粮中支链氨基酸水平对仔猪血液生化指标和部分免疫指标的影响

试验探讨了母猪日粮中添加支链氨基酸对哺乳仔猪血清生化指标和部分免疫指标的影响。选取胎次、体况、分娩期相近的法系(JALAX)母猪144头,随机均分成3个处理(对照组、处理A和处理B),每个处理6个重复,每个重复8头母猪。对照组饲喂基础日粮(总支链氨基酸为3.24%,缬氨酸:赖氨酸=0.86:1),处理A日粮添加低水平支链氨基酸(总支链氨基酸为3.56%,缬氨酸:赖氨酸=1.10:1),处理B日粮添加高水平支链氨基酸(总支链氨基酸为3.74%,缬氨酸:赖氨酸=1.20:1)。试验结果表明:①支链氨基酸添加组仔猪10、21日龄血清尿素氮水平有所降低,但10日龄血糖的浓度显著提高(P<0.05);②低水平支链氨基酸显著提高了10日龄仔猪血清白蛋白浓度(P<0.05)以及10、21日龄血清中乳酸脱氢酶活性(P<0.01);③与对照组相比,支链氨基酸的添加极显著提高了10、21日龄仔猪血清中IgG的浓度(P<0.01)。这说明母猪日粮中添加支链氨基酸能通过母体效应进而影响仔猪生长发育与免疫功能,但作用效果与添加水平有关。     

Inhibitory effects of isoleucine and antagonism of the other branched-chain amino acids on fermentation parameters by mixed ruminal microbes in batch cultures and rumen simulating fermenters (Rusitec)

The inhibitory effect of isoleucine (Ile) and antagonistic effect of leucine (Leu) and valine (Val) against the inhibition by Ile were investigated using simple batch and semicontinuous cultures of mixed ruminal microbes under feeding conditions using ordinary feed (timothy hay and corn grain). In the batch culture experiment, supplementation with Ile inhibited digestion and fermentation at 8–24 h of incubation as the concentration of Ile increased up to 5 mmol/L, but these inhibitions diminished at 48 h. The inhibition caused by Ile was mitigated by the addition of Leu and Val. In a semi‐continuous culture experiment using Rusitec, digestion and fermentation of the diet was suppressed by the administration of 1 and 5 mmol/L of Ile. The daily yield of microbial‐N was also reduced by Ile, but the density of the protozoa was not. The presence of Leu and Val alleviated the inhibition by Ile. These results suggest that the dietary inclusion of Ile possibly represses the bacterial growth, feed digestion and fermentation in the rumen in ordinary feeding situations by feedback inhibition, which could be diminished in the presence of other branched‐chain amino acids. The influences of the passage and level of supplementation on inhibition by amino acids are discussed.     

美仁牦牛肉不同部位常规营养成分及氨基酸和脂肪酸测定分析

摘 要：选取放牧条件下体况良好、体重相近的甘南成年美仁公牦牛 6 头、母牦牛 4头进行屠宰,采取美仁牦牛肉的肩甲、背最长肌、股二头肌三个部位的分割肉。测定不同部位营养成分、氨基酸和脂肪酸。 结果显示：不同部位美仁牦牛肉的蛋白质含量为22.97%～23.07%,其中股二头肌蛋白质含量最低,背最长肌最高;脂肪含量为1.27%～2.49%,股二头肌脂肪脂肪含量较低,不足1.27%。氨基酸含量丰富,脂肪酸总量依次为肩甲、背最长肌、股二头肌上脑肉。通过对比分析不同部位美仁牦牛肉中营养成分、氨基酸和脂肪酸等含量存在差异。     

辽育白牛两部位牛肉营养成分和氨基酸组成的分析

对6头22～24月龄辽育白牛育肥牛的眼肉和腹肉的常规营养成分、氨基酸组成测定分析,结果表明:辽育白牛眼肉和腹肉的水分、蛋白质、脂肪、灰分含量分别为59.5%±3.02%、18.17%±1.22%、24.03%±4.48%、0.84%±0.09%和58.69%±1.21%、15.84%±1.22%、34.18%±7.01%、0.74%±0.04%;必需氨基酸、总氨基酸、必需/总氨基酸、必需/非必需氨基酸含量分别为6.04 g/100 g±0.15 g/100 g、16.4 g/100 g±0.19 g/100 g、36.83%±0.17%、58.3%±0.26%和6.59 g/100 g±0.18 g/100 g、17.72 g/100 g±0.18 g/100 g、37.19%±0.19%、59.21%±0.31%,蛋白质中必需氨基酸组成比例基本符合FAO/WHO的标准。因此,辽育白牛眼肉和腹肉主要营养成分和氨基酸含量构成较为理想,适合生产高档牛肉。     

Effects of branched-chain amino acids on immune status of young racing horses

High-intensity exercise and competition are associated with depressed immune function. Young horses, which participate in high-intensity exercise and competitions, are at increased risk for the development of infectious disease due to depression of immune function. The effects of branched-chain amino acid (BCAA) supplementation on the immune status of young racing horses were evaluated, determining whether BCAA might help to avoid or reduce immune suppression during exercise and competitions. Twenty horses (10 male and 10 female) were treated with BCAA supplementation; another twenty untreated horses (10 male and 10 female) constituted control group. Peripheral blood was collected from each animal and evaluated for lymphocyte subsets, phagocytosis analysis of monocytes and granulocytes, lymphocyte proliferative response, and expression of cytokine-encoding messenger ribonucleic acids (mRNAs). The numbers of CD4⁺, CD8⁺, and major histocompatibility complex (MHC) class II⁺ cells in females of the treated group were significantly higher than those in females of the control group. The lymphocyte proliferative response in female of the treated group also was significantly higher than that in females of the control group. In addition, expression of mRNAs encoding interleukin-1β (IL-1β) and interferon-γ (IFN-γ) in females of the treated group was significantly higher than that in females of the control group. There were no significant differences between males of the treated and control groups. The results of this study indicated the positive effects of BCAA supplementation in counteracting immunosuppression in young female racing horses during and following high-intensity exercise.     

Regulation of free glutamate content in meat by dietary lysine in broilers

Regulation of taste is important for improving meat quality and glutamate (Glu) is one of the important taste‐active components in meat. Here, the effects of dietary lysine (Lys) content on taste‐active components in meat, especially free Glu, were investigated. Fourteen‐day‐old broiler chicks (Gallus gallus) were fed on diets containing 100% or 150% of the recommended Lys content for 10 days. Concentrations of free amino acids in plasma, muscle and liver were measured. The levels of messenger RNAs (mRNAs) for enzymes related to Glu metabolism were determined in muscle and liver. The concentration of muscle metabolites was also determined. The free Glu content in muscle of chicks fed the Lys150% diet was increased by 44.0% compared with that in chicks fed the Lys100% diet (P < 0.01). The mRNA level of lysine α‐ketoglutarate reductase, which is involved in Lys degradation and Glu production, was significantly increased (P < 0.05) in the Lys150% group. Metabolome analysis showed that the Lys degradation products, muscular saccharopine, pipecolic acid and α‐aminoadipic acid, were increased in the Lys150% group. Our results suggest that free Glu content in muscle is regulated by Lys degradation. These results suggest that a short‐term feeding of high‐Lys diet could improve the taste of meat.     

支链氨基酸在哺乳母猪营养中的研究进展

支链氨基酸作为猪的必需氨基酸,具有重要的生物学功能,特别是对泌乳母猪生产性能影响的研究,近年来受到高度重视。日粮中添加适当比例支链氨基酸,对进一步提高母猪泌乳力、繁殖性能、仔猪生产性能等都有重要意义。     

Efficiency of amino acid utilization in the growing pig at suboptimal levels of intake: branched-chain amino acids, histidine and phenylalanine + tyrosine

Five balance experiments on growing pigs were carried out to study the marginal efficiency of utilization of isoleucine, leucine, valine, histidine and phenylalanine + tyrosine and to estimate their requirements for maintenance. Purified diets based on casein and crystalline amino acids as the sole source of N contained graded levels of each amino acid, corresponding to protein accretion rates of 0, 33, 66, 99 and 132 g/day, respectively. All other essential amino acids were given in a 30% excess. N retention increased linearly (p < 0.01) as the dietary concentration of the limiting amino acid increased. Based on linear regression equations relating amino acid deposition in body protein to amino acid intake, marginal efficiencies of ileal digestible amino acid utilization were calculated to be isoleucine - 0.81, leucine - 0.81, valine - 0.82, histidine - 1.17 and phenylalanine + tyrosine - 0.67. Extrapolating the regression equations to zero N retention, the daily requirements of amino acids for N equilibrium were estimated to be (mg/kg0.75) isoleucine - 18, leucine - 33, valine - 23, histidine - 14 and phenylalanine + tyrosine - 43.     

日粮多不饱和脂肪酸对畜禽肉品质的影响

近年来,因为多不饱和脂肪酸(Polyunsaturated fatty acids,PUFA)独特的生物学功能,富含PUFA的畜禽产品的开发与利用成为热点,同时PUFA对畜禽肉品质的影响也备受关注。日粮中添加PUFA能够增加肉品中PUFA的含量,提高营养价值,但PUFA的强氧化性对其他肉品指标会产生影响。本文叙述PUFA对畜禽肉产品脂肪沉积、嫩度、系水力、风味和贮存性状等方面的影响,旨在为畜禽日粮的配制和人类膳食提供指导。     

肉鸭氨基酸营养需要量的研究进展

文章综述了氨基酸需要量评定方法,肉鸭几种主要必需氨基酸需要量,肉鸭氨基酸需要量推荐标准以及氨基酸理想模式,并展望了肉鸭氨基酸营养今后的研究方向。     

The effects of dietary concentrations of minerals, source of protein, amino acids and antibiotics on the growth of and digestibility of amino acids by broiler chickens

1. The effects of dietary calcium, available phosphorus, amino acid and antibiotic supplements on the digestibilities of amino acids and growth of broiler chickens were investigated in two experiments. 2. The performance of chickens fed on diets containing high concentrations of calcium and available phosphorus was poorer with meat meal-based diets than with soyabean-based diets. Methionine supplementation improved the performance of chickens fed meat meal-based diets. 3. A high dietary content of calcium (25.9 vs 11.8 g/kg) reduced chick performance and the digestibility of glutamic acid, leucine and phenylalanine but increased the digestibility of lysine and histidine. 4. High dietary contents of calcium and available phosphorus (24.3 and 13.0 vs 11.8 and 4.0 g/kg) reduced chick performance and the digestibilities of most amino acids. 5. Antibiotic supplementation did not improve the performance of chickens, but increased the digestibilities of most amino acids in chickens fed on diets with a high calcium or high calcium and available phosphorus contents. 6. It was concluded that excess dietary calcium alone, or calcium and phosphorus together, reduced chick performance and the digestibilities of most amino acids. Growing chickens tolerated excess dietary calcium and available phosphorus better in well-balanced amino acid diets, such as soyabean meal or methionine-supplemented meat meal diets, than in poorly balanced amino acid diets, such as unsupplemented meat meal diets.     

Effect of dietary excess of branched‐chain amino acids on performance and serum concentrations of amino acids in growing pigs

Depressed performance and availability of some amino acids (AA) in pigs fed excess Leu diets appear to be related to lower feed intake. Surplus Ile and Val may help to overcome this effect. An experiment was conducted with 24 pigs (31.8 ± 1.2 kg initial BW) to evaluate the effect of dietary excess of either Leu alone or with surplus Ile and Val on performance and serum concentration (SC) of essential AA. Treatments were as follows: T1, basal diet; T2, basal plus 0.43% L‐Leu (excess Leu); T3, basal added with 0.43% L‐Leu, plus 0.20% L‐Ile and 0.25% L‐Val (excess LIV). The basal diet was formulated to contain 0.90% standardized ileal digestible Lys and added with crystalline L‐Lys, L‐Thr, DL‐Met, L‐Trp, L‐Leu, L‐Ile, L‐His and L‐Val to create essential AA:Lys ratios close to an ideal protein for growing pigs. All pigs were fed the same amount of feed twice a day (average, 3.42× the requirement of NEm). Blood samples were collected at 2.5 (absorptive) and 11.0 h (post‐absorptive) post‐prandial to analyse SC of AA. Excess of either Leu or LIV did not affect growth rate nor feed conversion. Excess Leu increased Leu SC and decreased Ile and Val SC (p < 0.05) at both absorptive and post‐absorptive phases, but excess LIV restored the SC of Ile and Val. The SC of other essential AA was not affected by excess of either Leu or LIV. The SC of all AA during absorptive, on average, was about two times higher than that of post‐absorptive phase. These results suggest that the reduced availability (SC) of Ile and Val in pigs consuming excess Leu diets is attributed to a reduced absorption and increased cellular degradation rates of them.     

Biochemical and physiological bases for utilization of dietary amino acids by young Pigs

Protein is quantitatively the most expensive nutrient in swine diets. Hence it is imperative to understand the physiological roles played by amino acids in growth, development, lactation, reproduction, and health of pigs to improve their protein nutrition and reduce the costs of pork production. Due to incomplete knowledge of amino acid biochemistry and nutrition, it was traditionally assumed that neonatal, post-weaning, growing-finishing, and gestating pigs could synthesize sufficient amounts of all "nutritionally nonessential amino acids" (NEAA) to support maximum production performance. Therefore, over the past 50 years, much emphasis has been placed on dietary requirements of nutritionally essential amino acids as building blocks for tissue proteins. However, a large body of literature shows that NEAA, particularly glutamine, glutamate, arginine and proline regulate physiological functions via cell signaling pathways, such as mammalian target of rapamycin, AMP-activated protein kinase, extracellular signal-related kinase, Jun kinase, mitogen-activated protein kinase, and NEAA-derived gaseous molecules (e.g., nitric oxide, carbon monoxide, and hydrogen sulfide). Available evidence shows that under current feeding programs, only 70% and 55% of dietary amino acids are deposited as tissue proteins in 14-day-old sow-reared piglets and in 30-day-old pigs weaned at 21 days of age, respectively. Therefore, there is an urgent need to understand the roles and dietary requirements of NEAA in swine nutrition. This review highlights the basic biochemistry and physiology of absorption and utilization of amino acids in young pigs to enhance the efficacy of utilization of dietary protein and to minimize excretion of nitrogenous wastes from the body.     

肉粉类产品氨基酸特征及其品质鉴别

肉骨粉、肉粉、肉松粉等肉粉类产品是肉类加工业的副产品 ,具有蛋白质含量丰富、价格相对便宜的特点 ,在饲料行业中被广泛用作蛋白原料。肉粉类产品来源于畜禽副产品、下脚料 ,由于来源的差异 ,制成的产品质量参差不齐 ,变异性大。还有一些厂家为了谋求不当利益 ,在肉粉类产品中掺杂使假 ,以次充好。我们通过对检测的近千份肉粉类产品的氨基酸含量的分析 ,总结了肉粉类产品氨基酸的特征 ,并结合显微镜镜检结果 ,用以鉴别肉粉类产品掺假情况。1　肉骨粉、肉粉、肉松粉氨基酸特征肉骨粉等是由不宜食用的畜禽躯体骨骼、胚胎、内脏及其他下脚料…