Rate and Efficiency of Gain in Hereford and Angus Bulls From Lines Selected for Rapid Growth on High-Energy and Low-Energy Diets

Abstract

. 1989. Rate and efficiency of gain in Hereford and Angus bulls from lines selected for rapid growth on high-energy and low-energy diets. Can. J. Anim. Hereford and Angus bull calves were obtained from lines selected for an average of 18 yr for rapid growth on a high-energy diet (concentrate) or a low-energy diet (forage). They were given a typical feedlot diet(70% concentrate and30% forage) in amounts about equal to 95% of the ad libitum intake and were slaughtered at a liveweight of 500 kg. Effects ofbreed, or ofthe selection diet given to the antecedents ofthe bulls, on rate and efficiency of gain of empty body, carcass, fat, protein, and energy were measured. Selection diet had no effect on rate or energetic efficiency of gain of the empty body or any of its constituents, nor on the distribution of the constituents of the gain between the carcass and the noncarcass portions of the empty body. This suggests that both selection diets exerted the same selection pressure for improved growth rate and feed efficiency when offspring resulting from selection were provided with a common high-energy diet and that either type of diet would, therefore, be appropriate for selecting animals for production systems that use high-energy diets. It was suggested that the main effect of selection was to increase the mature weight of the offspring. Comparing breeds, it was noted that Hereford bulls were heavier at birth, grew more slowly to weaning but more efficiently thereafter, and their carcasses were a smaller proportion of empty live weight than were those of Angus bulls. Animals were weighed every 2 wk, at 16 h after the previous feeding, and the allotment of feed was adjusted at that time. The animals were bedded on wood shavings and were allowed trace-mineralized salt and water free choice.Both concentrate and alfalfa cubes were sampled every day throughout the 4 yr of the experiment and the samples were pooled into one large batch that was used for a digestion trial at the end of the experiment. Composition and digestibility data are given in Table2. Procedures used for carrying out the digestibility trials were as described in an earlier report Maintenance energy requirements were estimated from a subsidiary experiment in which 24 bulls ranging from 280 to 520 kg liveweight were provided enough of the present feed, (70% concentrate, 3O% hay) to satisry their maintenance requirements according to data compiled by van Es (1978Es ( , 1980, and allowing their weights to reach equilibrium. This approach was based on the finding that body weights of cattle on fixed energy intakes eventually stabilized and remained fairly constant over long periods of time (Taylor et al. 1981

Evaluations of genotype×environment interactions of beef bulls performance-tested in feedlot or pasture

“…During the later part of the postweaning treatment the Polled Hereford bulls had faster gains than the Angus bulls. In agreement with the results of this study, Bailey and Lawson, (1989) reported that Hereford bulls were heavier at birth and grew more slowly to weaning but more efficiently thereafter, and their carcasses were smaller in proportion to empty live BW than those of Angus bulls. In conclusion, bulls from different performance lines for growth were distinguished when adjustments were made for prior management effects.…”

“…Angus bull calves had greater (P < 0.001) scrotal circumference at weaning (22.9 ± 0.3 vs 21.3 ± 0.3 cm, respectively) and ADG (0.95 ± 0.01 vs 0.85 ± 0.01 kg, respectively) than Polled Hereford bull calves. In agreement with these results, Bailey and Lawson (1989) reported that compared to Angus bulls, Hereford bulls were heavier at birth and grew more slowly to weaning but grew faster after weaning.…”

Effect of selection for feedlot gain, breed and age on growth hormone and growth hormone kinetics in bull calves

“…Basal GH, and V5s, Tq72, MCR and SR of GH were similar for lines selected on both diets. This supports the conclusion of Bailey and Lawson (1989a) that both diets exerted the same selection pressure for improved growth rate. They reported that the rate, energetic efficiency, and composition of gain of these bulls were not affected by the diet given their ancestors during selection.…”

“…Animals, handling protocol and diets fed are described in detail in Bailey and Lawson (1989a (Mears and Schaalje 1993). Blood samples were stored on ice, centrifuged at 4"C, and the plasma stored in polystyrene tubes at -40"C until GH determination.…”

“…Other RIA components were: NIH-GH-BI8 reference standard (0.81 IU mg-r), rabbitantibovine GH (Lot 3-28-VII supplied by the late Dr. L Geschwind, University of California, Davis, CA), goatantirabbit gamma globulin and rabbit immunoglobulin (G 8-2 SA and AgR-30, respectively, Antibodies Incorporated, Davis, CA (Winer 1962) (Bailey and Lawson 1989a), carcass evaluation and composition (Bailey and Lawson 1989b), and blood composition and its relation to gain (Bailey et al 1990) have been published. The presentpaper details the relationship between GH kinetics and gain in these calves.…”