本试验旨在研究在饲粮中添加过瘤胃蛋氨酸（RPMet）、过瘤胃赖氨酸（RPLys）对荷斯坦奶公牛肉用生产性能和肉品质的影响。采用完全随机试验设计，选择25头12月龄左右、体重相近的健康荷斯坦奶公牛，随机分为5组，每组5个重复，每个重复1头。对照组饲喂基础饲粮（牧场实用饲粮）；其余4个试验组分别在基础饲粮中添加RPMet 15 g/d（RPM组）、RPLys 30 g/d（RPL组）、RPLys 30 g/d+RPMet 15 g/d（RPL+M组）和RPLys 30 g/d+RPMet 15 g/d（同时基础饲粮粗蛋白质水平降低1.71%）[RPL+M（L）组]。预试期10 d，正试期150 d。结果表明：1）RPL+M组和RPL+M（L）组试验牛末重、平均日增重均显著高于对照组（P<0.05），料重比显著低于对照组（P<0.05），但这2组间差异不显著（P>0.05）；RPL+M（L）组养殖效益最高，为7.67元/（d·头），且高出RPL+M组0.32元/（d·头）。2）与对照组相比，饲粮中添加RPMet、RPLys对荷斯坦奶公牛净肉率无显著影响（P>0.05）；RPM组、RPL组、RPL+M组和RPL+M（L）组宰前活重显著增加（P<0.05），且以RPL+M组最高，但RPL+M组与RPL+M（L）组无显著差异（P>0.05）；RPL组屠宰率显著升高（P<0.05）；各试验组胴体产肉率和肉骨比均显著增加（P<0.05），但试验组间差异不显著（P>0.05）。3）饲粮中添加RPMet、RPLys对眼肌面积、剪切力、熟肉率、大理石花纹等级、pH和肉色等级均无显著影响（P>0.05）。4）饲粮中添加RPMet、RPLys对肌肉脂肪酸组成亦无显著影响（P>0.05）。综上所述，在饲粮中添加RPMet、RPLys可保持奶公牛同等的肉品质和肌肉脂肪酸含量，并在一定程度上提高奶公牛肉用生产性能；且添加RPMet和RPLys可替代部分蛋白质饲料，增加养殖效益。

This experiment was conducted to investigate the effects of rumen-protected methionine (RPMet) and rumen-protected lysine (RPLys) supplementations in diet on meat production performance and meat quality of Holstein bulls. Twenty five Holstein bulls aged about 12 months with similar body weight were selected and divided into 5 groups by random experiment design, and each group included 5 replicates with 1 bull per replicate. The control group was fed a basal diet (ranch practical diet), and the other 4 groups were fed the basal diet added with RPMet 15 g/d (RPM group), RPLys 30 g/d (RPL group), RPLys 30 g/d+RPMet 15 g/d (RPL+M group) and RPLys 30g/d+RPMet 15g/d (meanwhile dietary crude protein level was lowered 1.71%) [RPL+M(L) group], respectively. Adaptation and experimental periods lasted for 10 and 150 d, respectively. The results showed as follows: 1) RPL+M and RPL+M(L) groups had significantly higher finial weight, average daily gain than control group (P<0.05), and had significantly lower ratio of feed to gain than control group (P<0.05), but there were no differences between the above two groups (P>0.05); the highest economic benefit of farming was RPL+M (L) group [7.67 RMB/(d·bull)], which was 0.32 RMB/(d·bull) higher than that of RPL+M group. 2) Compared with control group, meat percentage was not affected by RPMet and RPLys supplementations (P>0.05); RPM, RPL, RPL+M and RPL+M(L) groups had significantly higher body weight before slaughter (P<0.05), and the value reached the highest in RPL+M group, but they were not significantly different from those in RPL+M(L) group (P>0.05); RPL group had significantly higher dressing percentage (P<0.05); all experimental groups had significantly higher meat percentage of carcass and ratio of meat to bone (P<0.05), and there were no significant differences among experimental groups (P>0.05). 3) RPMet and RPLys supplementations in diet had no significant effects on eye muscle area, shear force, cooked meat rate, marbling degree, pH and meat color degree (P>0.05). 4) There was no significant difference on muscle fatty acid composition (P>0.05). It is concluded that dietary supplementations of RPMet and RPLys can maintain similar meat quality and muscle fatty acid composition of Holstein bulls, and can improve meat production performance; and the supplementations of RPMet and RPLys can instead part of protein feed, and can increase the economic benefit of farming.