科研之友
微信
新浪微博
Facebook
分享链接
摘要
The objective of this study was to investigate the effect of 2 breeds, Holstein and Jersey, and their F(1) hybrid (Jersey x Holstein) on milk fatty acid (FA) concentrations under grazing conditions, especially conjugated linoleic acid (CLA) and n-3 polyunsaturated fatty acids because of their importance to human health. Eighty-one cows (27 per breed grouping) were allocated a predominantly perennial ryegrass pasture. Samples were collected over 2 periods (June and July). Breed affected dry matter intake and milk production and composition. Holstein cows had the highest dry matter intake (18.4 +/- 0.40 kg of DM/d) and milk production (21.1 +/- 0.53 kg of DM/d). Holstein and Jersey x Holstein cows had similar 4% fat corrected milk, fat yield, and protein yield; with the exception of fat yield, these were all higher than for Jersey cows. Milk fat concentration was highest for Jersey cows and lowest for Holstein cows, with the hybrid cows intermediate. Total FA and linolenic acid intake (1.09 +/- 0.023 and 0.58 +/- 0.012 kg/d, respectively) were highest for Holstein cows. In terms of milk FA, Holstein cows had higher contents of C14:1, cis-9 C18:1 and linoleic acid. In turn, Jersey and Jersey x Holstein cows had higher content of C16:0. Milk concentrations of neither the cis-9, trans-11 isomer of CLA nor its precursor, vaccenic acid, were affected by breed. Nevertheless, large variation between individual animals within breed grouping was observed for CLA and estimated Delta(9)-desaturase activity. There was some evidence for a negative heterotic effect on milk concentration of CLA, with the F(1) hybrid cows having lower concentrations compared with the mid parent average. Plasma FA profile did not accurately reflect differences in milk FA composition. In conclusion, there was little evidence for either breed or beneficial heterotic effects on milk FA content with human health-promoting potential, though significant within-breed, interanimal variation was observed.
- 出版日期2010-5
