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Genetic and Environmental Relationships among Economic Characters in Beef Cattle III. Evaluating Maternal Environment^{1, 2,}

U. S. Department of Agriculture

Abstract

The theoretical composition of paternal and maternal half-sib correlations, the correlations between offspring and dam, and offspring and sire were compared with observed values to estimate the influence of maternal environment. These comparisons suggest that maternal environment from conception to birth and from birth to weaning had a large influence on birth weight, gain from birth to weaning, and weaning score, but a small influence on yearling gain and yearling score. The results further suggest a negative correlation exists between maternal environment from birth to weaning and the traits weaning gain and score.

The consequences of selecting for various traits were examined particularly as to the effect on maternal environment. Selecting for weaning gain will increase genic value for growth response and to a slight extent increase genic value for maternal environment. Part of the gain made will be nullified by the negative genetic correlation between maternal environment and growth response. Where calves are raised by nurse cows selecting for weaning gain will increase growth response but, because of negative genetic correlation, will result in a loss of genic value for maternal environment. Selecting cows which produce heavy calves would place greater emphasis on milking ability than on growth response so far as the genic value of the cows is concerned. Similar results are expected for weaning score.

Selecting on the basis of gain from weaning to yearling age will increase the genic value for yearling gain but will cause a small loss in genie value for milking ability.

Heritability estimates taking maternal environment into account were: birth weight, .42; weaning weight, .19; weaning gain, .12; weaning score, .16; yearling gain, .40; yearling score, .27.

¹ Contribution from the Western Regional Project W-1, "The Improvement of Beef Cattle Through Breeding Methods."

² Acknowledgment is made to Superintendent J. R. Quesenberry, U. S. Range Livestock Experiment Station, Miles City, Montana, under whose supervision the data for this study were collected in cooperation with the Montana Agr. Exp. Sta.

³ Department of Animal Husbandry, University of Nebraska, Lincoln.