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Journal of Dairy Science Vol. 69 No. 9 2358-2369
© 1986 by American Dairy Science Association ®
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Effects of Age, Milk Replacer Composition, and Rumen Function on Lipogenesis in Adipose Tissue of Young Calves

M. S. Wijayasinghe1, N. E. Smith2 and R. L. Baldwin

Department of Animal Science, University of California, Davis 95616

ABSTRACT

Rates of utilization of glucose, acetate, and lactate and activities of selected enzymes were determined in vitro to evaluate the effects of age and diet on lipogenesis in perirenal adipose tissue of calves. Three-day-old Holstein bull calves were fed up to 12 wk of age on one of three dietary treatments: 1) a high carbohydrate milk replacer; 2) a high fat milk replacer; and 3) weaning at 6 wk of age from high fat replacer to calf starter. Adipose tissue biopsies were obtained from calves at 2, 5, 8, and 12 wk of age. Rates of fatty acid synthesis and activities of enzymes of the pentose phosphate and citrate cleavage pathways were increased in calves fed high carbohydrate milk replacer. These parameters were decreased in calves fed high fat replacer and were further depressed after weaning. Substrate preference for fatty acid synthesis in all calves was acetate, then lactate, then glucose. With increase in age from 2 to 12 wk, adipose tissue of calves fed milk replacer partitioned more acetate and lactate toward fatty acid synthesis and less toward oxidation. The pentose phosphate cycle was characterized by high rate of recycling and contributed at least 50% of reducing equivalents required for fatty acid synthesis. It appeared that several features of lipogenesis characteristic of functional ruminants are also shared by preruminant calves.

FOOTNOTES

1 Department of Animal Science, University of Alberta, Edmonton, Alberta T6G 2P5, Canada.

2 Ruminant Research Department, Ralston Purina Company, Route 2, Box 423, Gray Summit, MO 63139.






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Copyright © 1986 by the American Dairy Science Association ®.