J. Anim Sci.
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J. Anim Sci. 1953. 12:10-14.
© 1953 American Society of Animal Science
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Repeatability, Heritability and the Effect of Level of Milk Production on the Occurrence of First Estrus after Calving in Dairy Cattle1

Durward Olds and D. M. Seath2

Kentucky Agricultural Experiment Station

Abstract

The average length of time from calving to first estrus for 472 normal parturitions of 210 cows was 32.1 ± 18.6 days. Analysis of the data indicated that individual cows had a tendency to repeat a similar length of time between calving and first estrus at successive parturitions.It appears that one previous observation on a cow would eliminate about 29 percent of the variance in predicting future performance in respect to the occurrence of heat after calving.

Level of milk production was found to account for about 0.9 percent of the variation in time from calving to first heat.

Heritability for time interval from calving to first estrus was estimated to be 27 percent when based on the intra-sire regression of daughter on dam using only the first available records for each animal.When all records were used, the heritability estimate was 32.2 percent.The correlation between paternal half-sibs indicated a heritability that was too small to be measured when based on single records but was 31.1 percent when all records were used.

Footnotes

1 The investigation reported in this paper is in connection with a project of the Kentucky Agricultural Experiment Station and is published by permission of the director.

2 The authors wish to acknowledge the assistance of Gene Holtzclaw and James Perkins in making the tabulations for this study.






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Copyright © 1953 by the American Society of Animal Science.