Weisbjerg Martin Riis, Wiking Lars, Kristensen Niels Bastian, Lund Peter
Faculty of Agricultural Sciences, University of Aarhus, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark.
J Dairy Res. 2008 May;75(2):142-52. doi: 10.1017/S002202990800318X.
The present study tested the hypothesis that supplemental dietary fatty acids (FA) affect the energy corrected milk yield in proportion to the milk production level of dairy cows, and increase both long chain FA proportion of milk FA and milk fat globule diameter. Sixteen Danish Holstein cows were divided into four 4x4 Latin squares with two squares of medium yielding cows (32.2 kg energy corrected milk (ECM)/d; 158 days in milk (DIM)) and two squares of high yielding cows (40.0 kg ECM/d; 74 DIM). Experimental length was 12 weeks, with three weeks for each of the four periods. The four treatments were no supplementation (17 g FA/kg dry matter (DM)) and three diets with supplemented FA (29, 40, and 52 g total FA/kg DM, respectively) obtained by substituting barley with Palm Fatty Acid Distillate (PFAD) fat. Diets were offered as total mixed rations with 63% grass/clover silage (DM basis). Dry matter intake decreased with increasing FA supplementation, but net energy intake was not affected. The general linear responses to 10 g/kg DM increase in FA level were 1.1 kg ECM (P<0.0001), 0.061 kg milk fat (P<0.0001), 0.012 kg milk protein (P=0.09) and 0.052 kg lactose (P=0.0002) per day, and linear responses in milk composition were 0.39 g fat (P=0.07), -0.71 g protein (P<0.0001) and 0.05 g lactose (P=0.3) per kg milk, and 0.092 microm (P<0.0001) in milk fat average globule diameter. Fatty acid supplementation decreased short- and medium-chain FA and C16:0 and increased C18:1 proportions of total FA in milk. Supplemental dietary FA increased ECM yield but not in proportion to production level as anticipated, and increased average FA chain length and milk fat globule diameter.
补充膳食脂肪酸（FA）对能量校正奶产量的影响与奶牛的产奶水平成正比，并会增加牛奶脂肪酸中长链脂肪酸的比例以及乳脂肪球直径。16头丹麦荷斯坦奶牛被分为四个4×4拉丁方设计，其中两个方为中产奶牛（32.2千克能量校正奶（ECM）/天；泌乳天数（DIM）为158天），另外两个方为高产奶牛（40.0千克ECM/天；DIM为74天）。实验时长为12周，四个阶段各为期三周。四种处理方式分别为不补充（17克FA/千克干物质（DM））以及三种补充了FA的日粮（分别为29、40和52克总FA/千克DM），通过用棕榈脂肪酸蒸馏物（PFAD）脂肪替代大麦来获得。日粮以全混合日粮形式提供，其中青贮草/三叶草占63%（以DM计）。随着FA补充量的增加，干物质摄入量减少，但净能量摄入量未受影响。FA水平每增加10克/千克DM时，每天的一般线性反应为1.1千克ECM（P<0.0001）、0.061千克乳脂肪（P<0.0001）、0.012千克乳蛋白（P=0.09）和0.052千克乳糖（P=0.0002），牛奶成分的线性反应为每千克牛奶0.39克脂肪（P=0.07）、-0.71克蛋白质（P<0.0001）和0.05克乳糖（P=0.3），乳脂肪平均球直径增加0.092微米（P<0.0001）。补充脂肪酸降低了短链和中链脂肪酸以及C16:0的含量，并增加了牛奶中总脂肪酸中C18:1的比例。补充膳食脂肪酸增加了ECM产量，但并非如预期那样与生产水平成比例增加，同时增加了平均脂肪酸链长度和乳脂肪球直径。
