Year: 1984
Type: dissertation
Abstract: Evidence has been found that maternal effects are important sources of variation in mammals.In beef cattle, evidence has been found to support the hypothesis that maternal effects can reduce the expected response to selection for growth traits, especially preweaning growth.It is not clear whether maternal effects in preweaning growth of beef cattle are genetic or environmental.Therefore, the present research was conducted to study the nature and.magnitude of maternal effects in birth and weaning weight of Hereford cattle.The data used were the records of 4,423 noncreep-fed beef calves raised at the Northern Agricultural Research Center, Havre, Mt from 1938 to 1983.Least-squares, fitting constants method (Henderson III) and Restricted Maximum Likelihood procedures were used to estimate eighteen covariances between different types of relatives.The basic models included the fixed effects of line-year, age of dam, sex of calf, age of dam by sex interaction and the regressions of birth weight on birthdate of calf and weaning weight on weaning age of calf.The source of variation depicting the relative relationship was considered a random effect.Multiple regression procedures were used to obtain the nine parameters: additive genetic, dominance genetic and environmental direct and maternal variances and the covariance between the direct and maternal source in each case.All solutions showed a negative additive genetic correlation between additive direct effects and additive maternal effects (rG).The results were not clear regarding to the magnitude of rG for birth weight but the probable value for weaning weight was around -.60 to -.75.There was also evidence for a negative environmental correlation for maternal phenotype of the dam and daughter in the case of weaning weight.This path coefficient (fm) was calculated to be .08for birth weight and -.10 for weaning weight.After correcting the expectations of the covariances between relatives for fm, rG was still present and negative for both weights.The solutions showed that dominance was also involved in determining maternal effects in preweaning growth of beef cattle but its effects may be confounded with epistasis.
Author: R. J. C. Cantet
Language: English
Subfield: Genetics
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W2462723939