Health & Environmental Research Online (HERO)


Print Feedback Export to File
5346455 
Journal Article 
Seasonal variation in milk conjugated linoleic acid and Delta(9)-desaturase activity in dairy cows 
Lock, AL; Garnsworthy, PC 
2003 
79 
1 
47-59 
WOS:000180332600005 
The objective of this work was to study changes in the fatty acid profile of cows' milk throughout the year with particular emphasis on cis-9, trans-11 conjugated linoleic acid (CLA), a proven anticarcinogen, found predominantly in milk and meat from ruminants. During the winter months, a total mixed ration of grass and maize silages, brewers grains, cereals, soya and dairy concentrates was fed. Through the summer months, fresh grass was fed, with increasing levels of buffer feeding given as the summer progressed. The CLA content of milk in May, June and July was significantly higher (P < 0.05) than all other months, averaging 1.50 g CLA/100 g FAME compared with a mean of 0.77 g/100 g for the other months. Delta(9)-Desaturase activity was also greater in the summer. Milk fat produced during the summer contained significantly (P < 0.05) greater amounts of short-chain fatty acids at the expense of medium-chain fatty acids indicating that fresh grass may alter the pattern of fatty acids produced de novo in the mammary gland. Results suggest that fresh grass promotes the synthesis of CLA.in the dairy cow through an increase in Delta(9)-desaturase activity in the mammary gland and possibly other unknown, factors. (C) 2002 Elsevier Science B.V. All rights reserved. 
dairy cattle; milk fat; conjugated linoleic acid; Delta(9)-desaturase; fatty acid synthase