Bertrand J A, Pardue F E, Jenkins T C
Animal, Dairy, and Veterinary Sciences Department, Clemson University, SC 29634-0361, USA.
J Dairy Sci. 1998 Aug;81(8):2215-20. doi: 10.3168/jds.S0022-0302(98)75800-X.
The objectives of this experiment were to determine whether ruminally protected amino acids (AA) increased milk protein when this content was depressed by the addition of whole cottonseeds in the diets of early lactation Jersey cows. Treatments were 1) a control diet, 2) a diet containing whole cottonseed, and 3) a diet containing whole cottonseed and ruminally protected lysine and methionine. Cows were assigned to treatments at a mean of 7 d postpartum and remained on the experiment for 18 wk. Dry matter intake and yields of milk, milk fat, fat-corrected milk, and energy-corrected milk were not affected by treatment. Milk fat content tended to decrease for cows fed diets containing whole cottonseed. However, the percentages of milk protein, total N, and casein N were depressed by the addition of whole cottonseed and were increased by the addition of ruminally protected AA. Plasma concentrations of methionine, but not lysine, were increased when ruminally protected AA were fed, suggesting that lysine was the most limiting.
本试验的目的是确定在初产泽西奶牛日粮中添加全棉籽使乳蛋白含量降低时，瘤胃保护性氨基酸（AA）是否能提高乳蛋白含量。处理方式有：1）对照日粮；2）含全棉籽的日粮；3）含全棉籽以及瘤胃保护性赖氨酸和蛋氨酸的日粮。奶牛在产后平均7天被分配到各处理组，并持续试验18周。干物质采食量以及牛奶、乳脂、乳脂校正乳和能量校正乳的产量不受处理方式影响。饲喂含全棉籽日粮的奶牛，乳脂含量有降低趋势。然而，添加全棉籽会使乳蛋白、总氮和酪蛋白氮的百分比降低，而添加瘤胃保护性氨基酸则会使其增加。饲喂瘤胃保护性氨基酸时，血浆蛋氨酸浓度升高，但赖氨酸浓度未升高，这表明赖氨酸是最具限制性的。
