Effects of supplementation of saturated fatty acid on milk production and milk fatty acid profile of mid-lactating cows during hot weather.

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 (TH1) 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 (P0. 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 (P0. 05), and there were no differences among treatments in milk protein, lactose, milk urea nitrogen and somatic cell score (P0. 05). The contents of milk fat and total solid were increased linearly (P0. 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 (P0. 05). The contents of short-chain fatty acid in SFA 3.0 were lower than those in SFA 0 (P0.01) and SFA 1.5 (P0.05), 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 (P0.01). The contents of c9r11CLA 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.