Journal of Dairy Research

Table of Contents - 2003 - Volume 70, Issue 03  


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

C Richard Stockdale a1c1, Glen P Walker a1, William J Wales a1, Dawn E Dalley a2, Anne Birkett a3p1, Zhiping Shen a3 and Peter T Doyle a1
a1 Department of Natural Resources and Environment, Agriculture Victoria–Kyabram, Kyabram Dairy Centre, 120 Cooma Road, Kyabram, VIC 3620, Australia
a2 Department of Natural Resources and Environment, Agriculture Victoria Ellinbank, RMB 2460, Hazeldean Road, Ellinbank, VIC 3821, Australia
a3 Food Science Australia, Private Bag 16, Sneydes Road, Werribee, VIC 3030, Australia

Article author query
stockdale c   [PubMed][Google Scholar] 
walker g   [PubMed][Google Scholar] 
wales w   [PubMed][Google Scholar] 
dalley d   [PubMed][Google Scholar] 
birkett a   [PubMed][Google Scholar] 
shen z   [PubMed][Google Scholar] 
doyle p   [PubMed][Google Scholar] 

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.

(Received November 19 2001)
(Accepted April 22 2002)


Key Words: Conjugated linoleic acid; cereal concentrates; milk fat.

Correspondence:
c1 e-mail: Richard.Stockdale@nre.vic.gov.au
p1 Present address: National Starch and Chemical Company, 10 Finderne Avenue, Bridgewater, NJ 08807, USA.