Effects of Abomasal Infusions of Glucose and Proprionate on Milk Yield and Composition

Abstract

According to the glucogenic theory increased glucose availability is responsible for the low-milk fat problem that occurs when cows are fed high-grain, low-fiber diets. Abomasal infusions of glucose or propionate were used to test this theory. In the first trial, an average of 2.15kg of glucose (per cow) was infused daily for 5 days. Compared to the control treatment (water infusions), the glucose infusions increased glucose concentrations of plasma (65.93 to 70.27 mg/100ml) but had no significant effects on insulin in plasma. Milk yield increased 1.9kg per day while the percentages of milk fat and protein decreased slightly (.31 and .14) as a result of glucose infusions. However, daily yields of milk fat and protein were not affected significantly by the increased availability of glucose. In a second trial, propionate (15 moles/cow/day) was infused into the abomasum continuously for 5 days. Feed intake was reduced 2.53kg per day during propionate infusions. Milk yield, milk composition, and glucose and insulin concentrations in plasma were not affected by postruminal infusions of propionate.