Nianogo A J, Amos H E, Froetschel M A, Keery C M
Department of Animal and Dairy Science, University of Georgia, Athens 30602.
J Dairy Sci. 1991 Jul;74(7):2243-55. doi: 10.3168/jds.S0022-0302(91)78397-5.
Twelve multiparous Holstein cows calving in fall and 12 calving in summer were blocked into four groups and used in a 2 x 2 x 2 factorial to determine the effects of season of calving, dietary fat, and protein degradability on milk production and efficiency of NEL utilization in a 16-wk study. Blocks were assigned randomly to one of four dietary treatment combinations: 1) control concentrate plus soybean meal (high degradability protein supplement); 2) control concentrate plus a mixture of heated soybean meal and corn gluten meal (low degradability protein supplement); 3) a blend of the control concentrate and a concentrate containing 12.1% fat to provide 1 kg d-1 fat, plus soybean meal; and 4) concentrate as in diet 3 plus heated soybean meal and corn gluten meal. Nutrient intake, milk yield and composition, BW changes, and daily ambient temperature were monitored. Intake of DM appeared to be related to NDF intake but was not affected by fat, protein degradability, or calving season. Intake of NEL was increased by feeding fat. Digestabilities of DM and CP were increased and fiber was decreased by feeding fat. Percentage and yields of milk fat, SNF, and protein and 4% FCM production were higher in cows calving in fall. Milk fat percentage was low in all cows in the study. Efficiency of energy utilization for milk production was decreased in cows fed fat and calving in the summer and by low protein degradability during wk 5 to 8 of lactation. At high concentrate intake, calving season had more effect on milk production than level of fat or protein degradability.
12头秋季产犊的经产荷斯坦奶牛和12头夏季产犊的经产荷斯坦奶牛被分成四组，用于一项2×2×2析因试验，以确定产犊季节、日粮脂肪和蛋白质降解率对16周试验期内牛奶产量和净能利用效率的影响。区组被随机分配到四种日粮处理组合之一：1）对照精料加豆粕（高降解率蛋白质补充料）；2）对照精料加加热豆粕和玉米蛋白粉的混合物（低降解率蛋白质补充料）；3）对照精料与含12.1%脂肪的精料混合以提供1kg/d的脂肪，加豆粕；4）日粮3中的精料加加热豆粕和玉米蛋白粉。监测营养物质摄入量、产奶量和组成、体重变化以及每日环境温度。干物质摄入量似乎与中性洗涤纤维摄入量有关，但不受脂肪、蛋白质降解率或产犊季节的影响。饲喂脂肪可增加净能摄入量。饲喂脂肪可提高干物质和粗蛋白的消化率，降低纤维消化率。秋季产犊的奶牛乳脂、非脂固形物、蛋白质的百分比和产量以及4%标准乳产量更高。本研究中所有奶牛的乳脂率都较低。夏季产犊且饲喂脂肪的奶牛以及泌乳第5至8周蛋白质降解率低的奶牛，用于产奶的能量利用效率降低。在高精料摄入量时，产犊季节对产奶量的影响大于脂肪或蛋白质降解率水平。
