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Addition of protected and unprotected fish oil to diets for dairy cows. I. Effects on the yield, composition and taste of milk

Published online by Cambridge University Press:  22 November 2002

PIERRE LACASSE
Affiliation:
Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, P.O. Box 90, Lennoxville, QC, Canada J1M 1Z3
JOHN J. KENNELLY
Affiliation:
University of Alberta, Department of Agricultural, Food and Nutritional Science, Edmonton, AB, Canada T6G 2P5
LOUIS DELBECCHI
Affiliation:
Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, P.O. Box 90, Lennoxville, QC, Canada J1M 1Z3
CHARAF E. AHNADI
Affiliation:
Agriculture and Agri-Food Canada, Dairy and Swine Research and Development Centre, P.O. Box 90, Lennoxville, QC, Canada J1M 1Z3 Present address: Département de biochimie clinique, Centre universitaire de santé de l'Estrie, 3001, 12ème Avenue nord, Sherbrooke (Québec), Canada J1H 5N4.

Abstract

Thirty Holstein cows in mid-lactation (158±20 DIM) were given a total mixed ration based on grass silage, maize silage and rolled barley. After a preliminary period of 1 week, this diet was supplemented with nothing (control), unprotected fish oil (3.7% of dry matter, DM), or two levels of glutaraldehyde-protected microcapsules of fish oil (1.5% and 3.0% of DM, respectively). Unprotected and protected supplements contained, respectively, 74% and 58% of DM as lipids. Cows given the unprotected supplement reduced their feed intake by >25%. Consequently, these cows lost body weight and produced less milk. DM intake, body weight, and milk yield were unaffected by protected fish oil. Fish oil reduced both milk fat and protein percentages, and decreased the proportion of short-chain fatty acids, stearic, and oleic acids in milk fat. Milk trans C18[ratio ]1 fatty acids increased in cows given both unprotected and protected fish oil. Milk fat content of very-long-chain n3 polyunsaturated fatty acids, including C20[ratio ]5 and C22[ratio ]6, increased with fish oil in the diet. Accordingly, the peroxide index increased and a taste panel was able to detect unusual taste in milk from cows consuming the higher level of protected fish oil and disliked the milk from cows given unprotected fish oil. In conclusion, when lactating cows consumed fish oil, milk concentration of long-chain n3 fatty acids increased and mammary de novo synthesis of fatty acids decreased, but milk yield and milk protein content were reduced, and the milk was more susceptible to oxidation and its taste was adversely affected.

Type
Research Article
Copyright
Proprietors of Journal of Dairy Research 2002

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