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Journal of Dairy Science Vol. 42 No. 12 1932-1943
© 1959 by American Dairy Science Association ®
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Relations between Weight at First Calving and Milk Production during the First Lactation1

R. H. Miller and L. D. McGilliard

Department of Dairy, Michigan State University, East Lansing

ABSTRACT

Michigan DHIA-IBM records for 4,677 Holsteins, 1,001 Guernseys, and 501 Jerseys were used to fit constants by least squares for the independent influences of age and weight on production in the first lactation. These effects indicated that delaying calving of heifers is economically disadvantageous and that heavier heifers have little or no advantage over lighter heifers of similar age.

Intraherd partial regressions were about 75 lb. of milk per month of age and 200 lb. of milk per 100 lb. weight at first calving. Large correlation between herd averages of weight and production contributed significantly to larger partial regressions of milk on weight when herds were ignored.

Genetic correlations between weight and production were of the order of .3. Heritabilities based on paternal-sister correlations ranged from .4 to .8 for weight and from .3 to .6 for production in the first lactation.

Dairy heifers should be bred as soon as large enough to minimize possible harmful effects on length of productive life. Selection for increased milk production may result in larger size. Correcting production for weight should be based only on the environmental part of the relationship between weight and production to avoid removing some genetic variation in production.

FOOTNOTES

1 Journal Article No. 2421. Michigan Agricultural Experiment Station.






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Copyright © 1959 by the American Dairy Science Association ®.