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Journal of Dairy Science Vol. 43 No. 1 63-75
© 1960 by American Dairy Science Association ®
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Rates of Improvement by Progeny Testing in Dairy Herds of Various Sizes1

L. W. Specht2 and L. D. Mc Gilliard

Department of Dairy, Michigan State University, East Lansing

ABSTRACT

Rates of genetic gain in milk production by progeny testing were examined, using characteristics of Michigan Holsteins. The production records from 34,073 Holsteins on DHIA test averaged 12,237 lb. of milk and 435 lb. of fat (305-2x-ME). AI daughters numbered 5,098 from 187 bulls and averaged 12,305 lb. of milk and 444 lb. of fat. Characteristics found were: repeatability, .46 for milk, .40 for fat; heritabilities from correlations between AI paternal sisters, .31 for milk, .23 for fat; regression of future AI daughters on first n tested AI daughters,
Figure 1
for milk and
Figure 2
for fat; average age at calving 4.4 yr.; cows removed annually, 26.3%, one-tenth involuntarily in each of the first four lactations and one-fourth in later lactations; and heifers born which come into production, 70%.

In herds of less than 100 cows, progeny testing was less efficient in improving the expected rate of genetic gain than the use of young sires selected on the basis of their dams' production. In herds of 100 and 200 cows, progeny testing had a slight advantage over the latter method.

Progeny testing in AI populations of 10,000 tested cows gave possibilities of annual genetic progress of from 1.7 to 2.3% of the average annual yield, depending upon the number of sires sampled and the proportion of those sampled which are selected for service. Further improvement seems possible if the percentage of cows on test were increased and if more efficient use were made of the tested bulls in AI service.

FOOTNOTES

1 Journal Article No. 2470 from the Michigan Agricultural Experiment Station.

2 Present address: Dairy Science Extension, Pennsylvania State University, University Park.






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