Relationship of Certain Milk Fat Depressing Diets to Changes in the Proportions of the Volatile Fatty Acids Produced in the Rumen

Abstract

Twelve high-producing Holstein cows were used to study the effect of feeding cod-liver oil and a high grain-restricted roughage ration on milk and fat production, fatty acid composition of the milk fat, and the proportions of volatile fatty acids in the rumen. The cod-liver oil and high-grain rations did not significantly alter milk production when compared to a control ration; however, these rations did significantly lower the fat content of the milk produced. When cod-liver oil was added to a normal ration of hay and grain, the proportions of the volatile fatty acids in the rumen were unaltered whereas the high grain ration caused a significant decrease in the proportion of acetate and a significant increase in propionate. It was concluded that cod-liver oil exerts its effect on milk-fat production somewhere beyond the rumen.