Effects of the Addition of Bentonite to High-Grain Dairy Rations which Depress Milk Fat Percentage

Abstract

Twelve lactating tIolstein cows were placed on an experiment consisting of three periods: four-week normal control, six-week fat depression, and six-week treat- ment. In the last period the cows were divided into three groups and allotted to three treatments: I. Fat-depressing ration, IL Fat-depressing ration + 5% bentonite, and III. Fat-depressing ration + 10% bentonite. A highly significant increase in milk fat per cent was noted in both bentonite treat- ments versus the fat-depressing ration, but there was no significant difference between the two levels of bentonite. The cows in Treatments I, II, and III maintained per cent milk fat at 86, 144, and 144% of the fat-depressing period, and 60, 87, and 87% of the normal control period, respectively. )~ilk production was significantly higher for Treatment II. A significant increase in the proportion of rumen acetate, along with a decrease in propionate and valerate~ was noted in the two bentonite treatments com- pared to the fat-depressing ration. There was a significant increase in the arterio- venous difference of blood acetate in the two bentonite treatments compared to the fat-depressing ration. Arteriovenous differ- ences for blood glucose and ketones and plasma free fatty acids and triglycerides were not altered significantly.