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Influence of pasture and concentrates in the diet of grazing dairy cows on the fatty acid composition of milk

Published online by Cambridge University Press:  21 July 2003

C Richard Stockdale
Affiliation:
Department of Natural Resources and Environment, Agriculture Victoria–Kyabram, Kyabram Dairy Centre, 120 Cooma Road, Kyabram, VIC 3620, Australia
Glen P Walker
Affiliation:
Department of Natural Resources and Environment, Agriculture Victoria–Kyabram, Kyabram Dairy Centre, 120 Cooma Road, Kyabram, VIC 3620, Australia
William J Wales
Affiliation:
Department of Natural Resources and Environment, Agriculture Victoria–Kyabram, Kyabram Dairy Centre, 120 Cooma Road, Kyabram, VIC 3620, Australia
Dawn E Dalley
Affiliation:
Department of Natural Resources and Environment, Agriculture Victoria Ellinbank, RMB 2460, Hazeldean Road, Ellinbank, VIC 3821, Australia
Anne Birkett
Affiliation:
Food Science Australia, Private Bag 16, Sneydes Road, Werribee, VIC 3030, Australia Present address: National Starch and Chemical Company, 10 Finderne Avenue, Bridgewater, NJ 08807, USA.
Zhiping Shen
Affiliation:
Food Science Australia, Private Bag 16, Sneydes Road, Werribee, VIC 3030, Australia
Peter T Doyle
Affiliation:
Department of Natural Resources and Environment, Agriculture Victoria–Kyabram, Kyabram Dairy Centre, 120 Cooma Road, Kyabram, VIC 3620, Australia

Abstract

In five short-term experiments conducted in Victoria in 1997 and 1998, grazing dairy cows were given either pasture alone or pasture supplemented with high-energy concentrates, and the fatty acid profiles of milk fat were measured. We established the effects of these feeds on some aspects of milk fat of importance for human nutrition, but we specifically focused on the hypothesis that conjugated linoleic acid (CLA) concentrations in milk fat increase as pasture intake increases, and decrease as more concentrates are fed. In agreement with previous research, feeding fresh pasture alone resulted in high concentrations (1·0–1·8 g/100 g milk fat) of CLA. When the effect of level of pasture consumption on CLA content was examined, a significant positive relationship (r2=0·35; P<0·05) was obtained. When cereal grain concentrates were used to supplement pasture intake, the CLA content of milk fat generally declined (P<0·05), except where the amount of concentrates given led to a marked reduction in total milk fat concentration. The use of cereal grain concentrates also generally resulted in significant (P<0·05) increases in medium-chain saturated fatty acids, but always reduced the contribution of butyric acid to milk fat, from 4·5 to 3·9 g/100 g milk fat, on average.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 2003

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