本试验旨在研究饲粮添加不同碳链长度脂肪酸对泌乳奶牛生产性能及乳脂肪酸组成的影响。以36头胎次、泌乳阶段和生产性能等接近的荷斯坦奶牛为试验动物，采用完全随机区组试验设计分为3个组，每组12个重复，每个重复1头奶牛。Ⅰ组为对照组，饲喂基础饲粮；Ⅱ组为短链和中链脂肪酸（short- and medium-chain fatty acids，SMCFA）组，饲喂基础饲粮+400 g/d SMCFA；Ⅲ组为长链脂肪酸（long chain fatty acids，LCFA）组，饲喂基础饲粮+400 g/d LCFA。饲养试验持续63 d，其中预试期7 d，正试期为56 d。结果表明：1）SMCFA组乳脂率显著高于LCFA组（P<0.05），各组间产乳量和乳中其他常规成分差异不显著（P>0.05）；2）饲粮中添加LCFA显著降低乳脂中C12∶0和C14∶0含量（P<0.05）；3）饲粮添加SMCFA显著提高乳脂中C12∶0和C14∶0含量，但显著降低C18∶0、c-9-C18∶1含量（P<0.05）；4）饲粮添加不同碳链长度脂肪酸对乳腺中硬脂酰辅酶A去饱和酶（Δ-9去饱和酶）活性没有显著影响（P>0.05）。结果提示，泌乳奶牛饲粮添加SMCFA对奶牛乳脂合成贡献大于LCFA，其中乳脂中C12∶0和C14∶0含量的提高对乳脂率的上升有重要影响。
This experiment was conducted to study the effects of supplemental fatty acids with different carbon chain lengths on yield and fatty acid composition of milk in lactating dairy cows. Thirty-six Holstein dairy cows, which had the adjacent birth order, lactation stage and milk yield, were selected in a completely randomized design and divided into 3 groups with 12 replicates per group and 1 dairy cow per replicate. Group Ⅰ was the control group, and the cows in this group were fed the basal diet; group Ⅱ was the short- and medium-chain fatty acids (SMCFA) group, and the cows in this group were fed the basal diet supplemented with 400 g/d SMCFA; group Ⅲ was the long chain fatty acids (LCFA) group, and the cows in this group were fed the basal diet supplemented with 400 g/d LCFA. Total duration of the experiment was 63 days (7 days for adaptation and 56 days for trial period). The results showed as follows: 1) the milk fat percentage in SMCFA group was significantly higher than that in LCFA group (P>0.05), while no differences in milk production and other milk components were observed for all groups (P>0.05); 2) LCFA supplementation decreased the contents of C12∶0 and C14∶0 in milk fat (P<0.05); 3) the contents of C12∶0 and C14∶0 in milk fat were significantly increased, whereas the contents of C18∶0 and c-9-C18∶1 in milk fat were significantly decreased by adding SMCFA (P<0.05); 4) the stearoyl-Co A desaturase (Δ-9 desaturase) activity in mammary gland was not significantly different among the 3 groups (P>0.05). These results indicate that supplementation of SMCFA has more contribution to the milk fat percentage compared with LCFA, which has something to do with the increasing contents of C12∶0 and C14∶0 in milk fat.［Chinese Journal of Animal Nutrition, 2011, 23（7）：1116 -1122］
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