Doctoral Dissertations

Date of Award

12-1971

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

R.R. Shrode

Committee Members

W.T. Butts, L.M. Josephson, D.O. Richardson, K.M. Barth

Abstract

Records accumulated from Brahman, Angus, Africander and their crosses during the period 1934 through 1962 at the Iberia Livestock Experiment Station, Jeanerette, Louisiana, were studied to estimate heterosis, compare birth weights, weaning weights and weaning type scores of straightbred and crossbred calves and to estimate retained heterosis in inter se matings of initial crosses. Significant differences (P < .01) were found between calves of Angus dams and Brangus and Brahman dams in birth weight (65.5 vs. 61.1 lbs) and weaning weight (417 vs. 449 lbs.) but not in weaning type (11.10 vs. 10.89). Also, calves of Brangus dams were significantly different (P < .01) from Brahman dams in birth weight (64.9 vs. 57.3), but no differences were found in weaning weight (458 vs. 440) or type at weaning (10.88 vs. 10.90) of calves from these two kinds of dams. Angus-sired calves were significantly (P < .01) different in birth weight (60,6 vs, 63,8) and weaning type (11.70 vs, 10.59) from Brangus and Brahman-sired calves. They were lower in birth weight (61 vs. 64 pounds) than Brangus-sired calves and higher (61 vs. 58 pounds) than Brahman-sired calves. No significant difference was found among these three kinds of sires with respect to weaning weight of their calves. There were no apparent differences between the birth weights of the straightbred calves and those of crossbred calves; however, the crossbreds were significantly (P < .01) heavier at weaning (453 vs. 409 pounds). The crosses graded lower (P < .05) than the straightbreds, although the average difference was small (10.91 vs. 11.04 where 1 equals 1/3 of a grade). Heterosis was significantly (P < .01) greater in the first cross Angus X Brahman (including the reciprocal) than in the first cross Angus X Brangus (including the reciprocal) for both birth weight and weaning weight. It should be noted that calves out of Brahman cows and sired by Angus bulls were lighter at birth by 14 pounds but heavier by 8 pounds at weaning than calves from the reciprocal of this mating. The same effect was evident in the Angus-sired calves from Brangus cows. Inter se mated Brangus progeny averaged 64 pounds in birth weight, 448 pounds in weaning weight or 59 pounds above the average of the parental straightbreds and 6 pounds below the average of first crosses. These figures indicate a retention of about 90 percent of the heterotic effect after approximately two complete generations of inter se mating, when measured as the ratio of the deviation of these means above contemporaries of the breeds which formed the hybrid to the corresponding deviations of the first cross of the parental breeds. Inter se mated Africander-Angus progeny weighed 63 pounds at birth and 404 pounds at weaning and graded slightly lower at weaning than the average of all calves. These calves were similar in weight at weaning to Angus calves but graded somewhat lower. Progeny from Africander-Angus cows mated to Angus bulls were heaviest of the crosses including Africander or Africander-Angus at both birth and weaning (74 and 449 pounds) but graded lower by approximately one-third of a grade. When simple averages were used, the crosses to Angus and Brahman sires showed heterotic responses also. Africander-Angus females mated to Brahman sires had progeny which weighed 63 pounds at birth and 417 pounds at weaning and graded 11+ at weaning. A small group of Brahman cows bred to Africander males had calves weighing 66 pounds when born and 414 pounds at weaning, about the same as progeny from Africander-Angus cows mated to Brahman sires. These data indicate that crossbreeding and the increased weights at weaning time are advantageous to the producer. This is especially true for the producer of calves to be slaughtered at light weights in the Gulf Coast area for local consumption. The analyses showed significant heterosis in most crosses with the most pronounced effect in first crosses and a retention of an appreciable amount of heterosis by the second generation produced From inter se matings of crossbreds.

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