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 quali-ty 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 low-ered 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 a-mong 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.%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。
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