This experiment aimed to evaluate the effects of supplying 4 different inclusion levels of Met + Cys to crossbred liquid-fed calves on animal performance and body composition. Thirty-six Holstein-Gyr male calves were separated into 2 age groups: 16 calves, slaughtered at an age of 30 d, representing the physiological phase from 8 to 30 d, and 20 calves, slaughtered at an age of 60 d, representing the physiological phase from 30 to 60 d. At 8 d of age, the animals were randomly distributed among the experimental treatments: 4 Met + Cys inclusion levels (Met + Cys: 8.0, 8.7, 9.4, and 10.2 g/d), provided by an AA supplement added to 1.0 kg (as fed) of commercial milk replacer containing soy protein concentrate and wheat protein isolate reconstituted at 13.8% (dry matter basis). The diet was supplied without allowing leftovers and no starter feed was provided. The experimental diets were supplied without allowing orts, so that the dry matter, crude protein, and ether extract intakes were the same for all animals, independent of Met + Cys level. Total weight gain, average daily gain, gain composition, and body composition were evaluated for both age groups separately. Digestibility of organic matter, crude protein, and ether extract was lower for 8 to 30 d than for 30 to 60 d. The effect of Met + Cys levels on the digestibility of nutrients was not observed; there also was no significant interaction between physiological phase and Met + Cys levels. For the 8 to 30 d group, no responses in performance were observed according to the different Met + Cys levels, which indicates that 8.0 g/d of Met + Cys met the requirements for this physiological phase. The 30 to 60 d group responded positively to higher Met + Cys inclusion in the diet. In conclusion, an optimal Met + Cys dietary level to ensure best performance and protein gain ranges from 8.41 to 9.81 g/d.

该实验旨在评估向杂种液饲犊牛提供4种不同含量的Met + Cys包合水平对动物性能和身体组成的影响。将36只Holstein-Gyr雄性犊牛分为2个年龄组：16头犊牛，在30 d时被宰杀，代表了8到30 d的生理阶段； 20头犊牛，在60 d时被宰杀，代表了生理阶段。生理期为30到60 d。在8天大时，将动物随机分配到以下实验处理中：4 Met + Cys包涵体水平（Met + Cys：8.0、8.7、9.4和10.2 g / d），由添加至1.0 kg的AA补充剂提供（含大豆蛋白浓缩物和小麦蛋白分离物的商业代乳品，以13.8％（以干物质计）重构。提供的饮食不允许剩菜剩饭，也没有提供起步饲料。提供实验饮食时不加糖，因此所有动物的干物质，粗蛋白和乙醚提取物的摄入量均相同，不受Met + Cys水平的影响。分别评估了两个年龄组的总体重增加，平均日增重，增重组成和身体组成。有机物，粗蛋白和乙醚提取物的消化率在8到30 d时比在30到60 d时要低。未观察到Met + Cys水平对养分消化率的影响；生理期和Met + Cys水平之间也没有显着的相互作用。对于8到30天的组，根据Met + Cys水平的不同，没有观察到对运动的反应，表明为8。0 g / d的Met + Cys满足该生理阶段的要求。30到60天的组对饮食中更高的Met + Cys含量有积极的反应。总之，确保最佳性能和蛋白质增高的最佳Met + Cys饮食水平范围为8.41至9.81 g / d。