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Thesis (M.S.)—University of Nebraska—Lincoln, 1949. Department of Animal Husbandry.


Copyright 1949, the author. Used by permission.


The importance of evaluating the breeding potentialities of domestic animals at an early age has long been recognized by livestock breeders. If phenotype at an early age is an expression of genotype, it should be possible to select superior individuals on the basis of their early performance. However, if the phenotype of an individual is dependent largely on factors other than genotype, an animal’s performance at these ages is of little value as a criterion of selection. More information on the factors that influence birth and weaning weights of beef calves is definitely needed to determine the effectiveness of selection based on these characters.

Previous work has yielded estimates of the heritability of birth and weaning weight of beef cattle. There seems to be a definite need for supporting work to establish more firmly the heritability estimates reported by previous workers. The factors that may influence a cow’s weight, from birth to weaning, may also affect the way in which her calf will lose or gain weight from its birth to weaning. This information may increase the present knowledge of the different factors that affect birth weight, weight gain between birth and weaning, and weaning weight and how these factors affect each weight stage.

Many have concluded that the fluctuation of a calf’s weight is only influenced to a limited degree by the genotype of the individual. However, others suggest that analysis of weight at birth, weight gain after birth, and weight at weaning may be useful during selection for performance in beef cattle. This inconsistency justifies additional investigation into debate.

The purpose of this study was to gain information on the relative importance of the different factors which influence birth weight, weight gain between birth and weaning, and weaning weight of beef calves. Factors influencing the birth weight of calves have been given more attention than the factors influencing weaning weight, or gain from birth to weaning.

Advisor: Cecil T. Blunn