| Abstract: | The idea has been advanced that Brahman dams produce calves of lower birthweights regardless of sire breed type. Birth records on 3595 individuals were collected between 1950 and 1970 at the Texas Agricultural Experiment Station at McGregor, Texas. These data were analyzed to determine the validity and extent of this restriction in birthweight. Raw means and variances were used to evaluate the data. Hereford sires showed more uniform birthweights than the Brahman and Brahman X Hereford sires. Brahman dams tended to produce calves of lower birth weight although the variance within the three mating types using Brahman dams were relatively dispersed. A least squares model was designed to correct the raw data for any extraneous sources of variation. An analysis of variance was performed and the following effects were found to be highly significanct (P < .01): Dam breed Dam age Year of calf birth Season of calf birth Calf sex Sire breed x dam breed interaction Parity and Sire breed approached significance at P = .05. No adequate explanation of the mechanism by which Brahman cows mediate birth weight was found. The research did add evidence to the hypothesis that Brahman cows tend to produce smaller calves, but they are capable of producing extremely large calves at times. |
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