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University of Guelph,3 Guelph, Ontario, Canada,4
Abstract
The effects of castration, energy intake, hormone implants and their interactions on the rate of gain, feed intake and feed efficiency were studied in two trials using 108 beef males. Bulls grew (P<0.05) more rapidly and more efficiently than steers on all energy levels and hormone implants. The energy intake was a limiting factor in the growth and dry matter conversion in all cattle.
The hormone implants increased daily gains and feed efficiency of steers by 10% in each trial, but this was significant (P<0.05) only in Trial 2. However, the same implants had no effect (P>0.05) on the performance of bulls. Reimplantation 98 days after the initial implants of diethylstilbestrol had no effect on the rate of gain or feed efficiency of the animals. A 50 mg implant of melengestrol acetate in conjunction with a 36 mg implant of diethylstilbestrol did not affect the rate and efficiency of gain over a single diethylstilbestrol implant.
Carcass of bulls were as acceptable as those from steers. Greater percentages of the edible meat were found in the chuck, flank and shank of bulls than in steers. Steers had a greater percentage of the edible meat in the sirloin than did bulls. No consistent effect of hormone implants was observed in yield of edible meat.
1 The data are from a thesis submitted by the author to the Graduate School, University of Guelph, Canada in partial fulfillment of the requirements for the degree of Master of Science.
2 Present address: Research Station, Canada Agriculture, Lennoxville, Quebec.
3 Department of Animal and Poultry Science.
4 The authors wish to express their appreciation of the Ontario Department of Agriculture and Food for their support of this project.
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