Model to describe and alleviate milk protein depression in early lactation dairy cows fed a high fat diet.
The depression of milk protein percentages for cows fed high fat diets in early lactation is a major problem facing the dairy industry. In order to describe more fully the mechanism involved, data involved 97 cows observations were summarized. Cows were fed diets containing corn-soybean meal or additional fat in the form of whole oilseeds as the main ingredients in the concentrate mix. Blood samples from the tail artery and subcutaneous abdominal vein were taken approximately 6- to 8-wk postpartum for amino acid analyses. Production of milk during the week of blood sampling was increased (36.9 and 39.6 kg/d) approximately 7.3% but milk protein percentages (2.91 and 2.79) were reduced for cows fed added fat. Intake of DM (21.1 and 21.4 kg/d) and BW (605 and 608 kg) were similar. Uptake of amino acids by the mammary gland, as measured by arteriovenous differences, was numerically lower for all essential amino acids and significantly reduced for histidine, isoleucine, leucine, phenylalanine, threonine, valine, and total essential amino acids for cows fed added fat. It is proposed that added fat inhibits somatotropin release from the anterior pituitary, thereby reducing mammary gland uptake of amino acids because of the role of somatotropin in aiding amino acid uptake. Administration of exogenous somatotropin with added fat diets may alleviate milk protein depression associated with such diets.
Casper
D P
DP
Dairy Science Department, South Dakota State University, Brookings 57007-0647.
Schingoethe
D J
DJ
D000596:Amino Acids / Q000378:metabolism; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000502:physiology*; D004041:Dietary Fats / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D013006:Growth Hormone / Q000008:administration & dosage; D007774:Lactation / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000378:metabolism; D008892:Milk / Q000032:analysis; D008894:Milk Proteins / Q000096:biosynthesis*; D008954:Models, Biological; D011247:Pregnancy
D000596:Amino Acids; D004041:Dietary Fats; D005230:Fatty Acids, Nonesterified; D008894:Milk Proteins; D013006:Growth Hormone