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Effect of trenbolone acetate on urea metabolism in cattle fed low-protein roughage diets

Published online by Cambridge University Press:  27 March 2009

R. A. Hunter  and
T. Magner
R. A. Hunter
Affiliation:
CSIRO, Division of Tropical Animal Production, Tropical Cattle Research Centre, Box 5545, Rockhampton Mail Centre, Queensland, 4702, Australia
T. Magner
Affiliation:
CSIRO, Division of Tropical Animal Production, Tropical Cattle Research Centre, Box 5545, Rockhampton Mail Centre, Queensland, 4702, Australia
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Summary

In two experiments using cattle implanted with 0 or 300 mg trenbolone acetate and fed restricted diets of low-protein roughage, urea synthesis was measured by plasma dilution of a single intravenous injection of [14C]urea. Urea flow to the gut was calculated as the difference between synthesis and urinary urea output. Because rumen ammonia concentrations were only c. 1 mg/1, it was assumed that urea transfer from the gut to blood was negligible.

In the first experiment, fistulated heifers treated with trenbolone acetate synthesized significantly (P < 0·05) less urea (0·8 v. 1·2 g/h) and had a tendency to excrete less (P = 0·08) urea in urine (0·04 v. 0·14 g/h) and to have a lower (P = 0·07) flow of urea into the gut (0·8 v. 1·1 g/h) than untreated animals. They also had significantly (P < 0·01) lower rumen digestion rates, determined from disappearance of feed dry matter from nylon bags suspended in the rumen for 48 h.

In the second experiment, steers treated with trenbolone acetate synthesized significantly (P < 0·05) less urea (1·0 v. 1·9 g/h) and had a significantly (P < 0·05) lower flow of urea into the gut (0·9 v. 1·8 g/h) than untreated steers.

The results were consistent with an hypothesized sequence of events resulting from treatment with trenbolone acetate. The sequence proposed was a decrease in the rate of tissue protein breakdown, a decrease in the rate of urea synthesis from de-amination of amino acids, a decrease in the amount of urea recycled to the rumen, a decreased rumen digestion rate and thus a decrease in feed intake.

Type
Research Article
Information
The Journal of Agricultural Science , Volume 114 , Issue 1 , January 1990 , pp. 55 - 58
Copyright
Copyright © Cambridge University Press 1990

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