Depression in Percentage of Milk Fat by Parenteral Glucose Infusion and Glycerol Feeding

Abstract

Low roughage–high concentrate diets can profoundly depress the fat content of milk1–6. One of us has advanced the hypothesis6 that such depressions are the result of metabolic effects of an increase in the proportion of glycogenic to non-glycogenic products of digestion on such diets. Such an increase could be effected by a proportion of the starch escaping ruminal digestion, high ruminal lactic acid production, and an increased proportion of the glycogenic propionic acid in the products of ruminal digestion. There is evidence that low roughage–high concentrate diets have such effects5,7,8. It is also known that the proportions of fat and carbohydrate in the diet of animals can profoundly affect their carbohydrate and lipid metabolism, and changes, although erratic, in blood lipids have been recorded on low roughage diets5,9, indicating some disturbance of lipid metabolism.