RELATIONSHIP BETWEEN DIETARY-FAT SUPPLEMENTATION AND MILK PROTEIN-CONCENTRATION IN LACTATING COWS - A REVIEW

Changes in protein concentration in milk of dairy cows resulting from supplementation of diets with fat reported during the last two decades have been compiled, and the existing literature concerning dietary fat and milk protein reviewed. Data show that increasing fat content of diets has generally increased milk yields but decreased milk protein concentrations. The decrease in protein concentration has been hypothesized to be due to decreased glucose availability, development of insulin resistance, increased efficiency of milk production, or reduced plasma somatotropin. In this review, data are presented which attribute the decrease to a lack of increase in amino acids available to the mammary gland for protein synthesis as milk yield increases during fat supplementation.