Effects of Feeding a Zero- or High-Roughage Diet to Cattle upon Adipose Tissue Lipogenesis

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Abstract
Hereford steer calves were fed whole shelled corn or corn silage diets to determine the effect of dietary roughage level on lipogenic enzymes of adipose tissue. In Trial 1, perirenal and subcutaneous adipose tissue were taken post-mortem from 32 steers who had been fed either diet ad libitum for at least 175 days and weighed 450 kg live. In Trial 2, for which a changeover design was used, six cattle were fed both diets so that energy intake was calculated to be equal for each. Perirenal adipose tissue was taken in the second trial by biopsy when the steers weighed 200 kg live. In Trial 1, compared to high-roughage, the zero-roughage diet elicited from a two- to fourfold increase (P < 0.05) in activity of pentose phosphate pathway dehydrogenases of adipose tissue. This dietary effect was not observed in Trial 2. In both trials, acetyl-CoA synthetase activity and fatty acid synthesizing capacity from acetate of adipose tissue were unaffected by diet. Carcasses from animals fed the zero-roughage diet in Trial 1 contained 6% more separable fat (P < 0.05) than carcasses from animals fed the high-roughage diet. The mean of both trials for plasma acetate from animals fed the zero-roughage diet was 0.61 μmol/ml, which was less (P < 0.05) than 0.95 μmol/ml, which was the comparable value determined from animals fed the high-roughage diet. Plasma propionate was increased (P < 0.05) by feeding the zero-roughage diet in both trials but accounted for less than 20% of volatile fatty acids in all samples examined.

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