本文旨在研究饱和脂肪酸对高温环境条件下泌乳中期奶牛产奶性能和牛奶中脂肪酸组成的影响。选择产后150～210d的中国荷斯坦奶牛48头，根据产奶量、分娩时间和胎次分为对照组（SFA 0）、1.5%(SFA 1.5)和3.0%(SFA 3.0)饱和脂肪酸试验组。试验期间牛舍最小湿热指数（THI）在72以上。试验结果，日粮添加饱和脂肪酸提高4％乳脂校正产奶量（P<0.05），SFA 1.5与SFA 3.0脂肪组之间差异不显著（P>0.05）。乳脂和总固形物含量，SFA 3.0组高于对照组（P<0.05），SFA 1.5组与对照组和SFA 3.0组间差异均不显著（P>0.05）。乳蛋白、乳糖、乳尿素氮和乳中体细胞评分各组间差异均不显著（P>0.05）。日粮添加饱和脂肪酸的量对乳脂和乳总固形物呈线性增加（P<0.05），对乳蛋白的含量呈二次曲线增加（P<0.05）。中链、长链、长链不饱和、总不饱和、t10c12CLA、总饱和脂肪酸、长链不饱和与总不饱和脂肪酸的比例各组间差异均不显著（P>0.05）。SFA 3.0组短链脂肪酸低于对照组(P<0.01)和SFA1.5组(P<0.05)，SFA 1.5组与对照组差异不显著（P>0.05）。日粮添加饱和脂肪酸呈线性降低乳中短链脂肪酸含量（P=0.03）和c9t11CLA含量（P<0.01），SFA 0、SFA 1.5和SFA 3.0组乳中c9t11CLA含量分别为0.72、0.64和0.55 g/100 g脂肪。结果表明，泌乳中期热应激奶牛日粮添加饱和脂肪酸可显著提高产奶量、乳脂率和乳中总固形物含量；对乳中脂肪酸组成无明显影响；c9t11CLA含量显著降低，但仍在正常范围之内。

The objective of this study was to investigate the effects of supplemental saturated fatty acid on milk yield, components and fatty acid profile of midlactating cows during hot weather. A total of 48 Chinese Holstein cows were divided into three groups according to randomly block design by milk yield, days in milk (DIM, 150～210 d) and parity, and were fed isonitroenous diets containing 0 (SFA 0), 1.5% (SFA 1.5) and 3.0% (SFA 3.0) saturated fatty acid, respectively. The minimum temperature humidity index (THI) was normally more than 72 during experimental period. Results showed that the milk yields were higher in SFA 1.5 and SFA 3.0 than those in SFA 0 (P<0.05), and there was no difference between SFA 1.5 and SFA 3.0. The contents of milk fat and total solid in SFA 3.0 were higher than those in SFA 0 (P<0.05), and there were no differences among treatments in milk protein, lactose, milk urea nitrogen and somatic cell score (P>0.05). The contents of milk fat and total solid were increased linearly (P<0.05) and milk protein was increased quadratically (P<0.05) by supplemental fatty acids. There were no differences among treatments in mediumchain, longchain, longchain unsaturated (LUFA), total unsaturated (TUFA), t10c12 conjugated linoleic acid (CLA), total saturated fatty acid and the ratio of LUFA to TUFA (P>0.05). The contents of short-chain fatty acid in SFA 3.0 were lower than those in SFA 0 (P<0.01) and SFA 1.5 (P<0.05), but there was no difference between SFA 0 and SFA 1.5. Supplemental saturated fatty acid decreased linearly the contents of mediumchain fatty acid （P=0.03） and c9t11CLA (P<0.01). The contents of c9t11CLA in SFA 0, SFA 1.5 and SFA 3.0 were 0.72, 0.64 and 0.55 g/100 g fat acid methyl esters, respectively. It was concluded that milk yield, milk fat content and total solid were improved by supplemental saturated fatty acid. There was no effect of supplemental saturated fatty acid on milk fatty acid profile except that c9t11CLA was decreased within a normal level.