Supplementation of dairy cows with a fish oil containing supplement and sunflower oil to increase the CLA content of milk produced at pasture.

摘要

Although supplementation of dairy cattle feeds with fish oil and vegetable oils increases levels of cis9, trans11 CLA in milk, high levels of oil can lead to detrimental effects on overall milk composition. Therefore, this study sought to determine whether feeding of relatively low levels of fish oil or sunflower oil could still lead to increases in milk contents of CLA. 40 cows on a diet of grazed grass were given supplements as follows: no supplement (P); 255 g/day sunflower oil (SO); 255 g/day SO + 52.5 g/day fish oil (FO); or 105 g/day FO. Supplementation increased milk yields (P < 0.01), protein yield (P < 0.05), lactose yield (P < 0.001) and lactose concn. (P < 0.01), but decreased concn. of milk fat (P < 0.05) and protein (P < 0.01). Both oils had similar effects on production variables. All supplementation treatments increased concn. of C18:1 trans9 + C18:1 trans11 (mainly C18:1 trans11; P < 0.01) and C18:2 cis9,trans11 CLA (P < 0.01). FO led to greater increases than SO. Overall, results suggest that supplements containing low levels of FO, either alone or in combination with SO could be used to increase the concn. of C18:2 cis9,trans11 CLA from the already high levels found in milk from pasture-fed cattle.