Drackley J K, LaCount D W, Elliott J P, Klusmeyer T H, Overton T R, Clark J H, Blum S A
Department of Animal Sciences, University of Illinois, Urbana 61801, USA.
J Dairy Sci. 1998 Jan;81(1):201-14. doi: 10.3168/jds.S0022-0302(98)75567-5.
The objectives of this experiment were to determine long-term responses to supplemental fat (from whole soybeans and liquid animal fat) and to determine whether the supplementation of nicotinic acid would enhance milk protein content or yield. From wk 4 through 43 postpartum, 44 multiparous Holstein cows (10 to 12 per treatment) were assigned to one of four dietary treatments: 1) control, 2) control plus 12 g/d of nicotinic acid, 3) supplemental fat, and 4) supplemental fat plus 12 g/d of nicotinic acid. The dry matter intake of cows did not differ among dietary treatments. Yields of milk, solids-corrected milk, and 3.5% fat-corrected milk were increased by nicotinic acid; the yield of fat-corrected milk during wk 4 to 25 was increased by supplemental fat. Contents of crude protein (CP) and true protein in milk were less for cows fed diets supplemented with fat or nicotinic acid; casein content was decreased by nicotinic acid. Intake of net energy for lactation was greater for cows fed supplemental fat; energy balance was greater during wk 4 to 25 for cows fed diets supplemented with fat. Body condition score and body weight were less when nicotinic acid was added to the control diet than when it was added to the diet supplemented with fat. Supplemental fat increased the concentration of nonesterified fatty acids (NEFA) in plasma; nicotinic acid increased NEFA when it was added to the control diet but decreased NEFA when it was added to the diet supplemented with fat. Nicotinic acid did not prevent the decrease in milk CP content that was induced by dietary fat, but it did increase milk yield and tended to increase the yield of milk CP.
本实验的目的是确定对补充脂肪（来自全脂大豆和液态动物脂肪）的长期反应，并确定补充烟酸是否会提高乳蛋白含量或产量。从产后第4周到第43周，44头经产荷斯坦奶牛（每组10至12头）被分配到四种日粮处理之一：1）对照组，2）对照组加12克/天的烟酸，3）补充脂肪组，4）补充脂肪加12克/天的烟酸组。不同日粮处理间奶牛的干物质采食量没有差异。烟酸提高了牛奶、标准乳和3.5%乳脂校正乳的产量；补充脂肪提高了第4至25周期间乳脂校正乳的产量。饲喂添加脂肪或烟酸日粮的奶牛所产牛奶中的粗蛋白（CP）和真蛋白含量较低；烟酸降低了酪蛋白含量。饲喂补充脂肪日粮的奶牛泌乳净能摄入量更高；饲喂补充脂肪日粮的奶牛在第4至25周期间能量平衡更好。在对照日粮中添加烟酸时，奶牛的体况评分和体重低于在补充脂肪日粮中添加烟酸时的情况。补充脂肪提高了血浆中非酯化脂肪酸（NEFA）的浓度；在对照日粮中添加烟酸时会提高NEFA浓度，但在补充脂肪日粮中添加烟酸时会降低NEFA浓度。烟酸不能防止日粮脂肪引起的牛奶CP含量下降，但它确实提高了牛奶产量，并倾向于提高牛奶CP产量。
