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Heritability and Repeatability of First, Second, Third, and Fourth Records of Varying Duration in Brown Swiss Cattle^{1, 2, 3,}

Dairy Husbandry Department, University of Wisconsin, Madison

ABSTRACT

Heritability estimates of first, second, third, and fourth lactations, averages of two, three, and four records, and of 100- and 200-day partial first lactations, were made to study the reliability of using partial or complete first records as the basis for early selection in Brown Swiss cattle. The data consisted of 8,413 HIR records of not less than 200 or more than 305 days in length from 38 Brown Swiss herds in Wisconsin.

Heritability estimates, obtained by doubling the intrasire regression of daughters on dams, were 0.42 for milk, 0.37 for butterfat, and 0.80 for percentage of butterfat for the first lactation. Estimates for milk and butterfat production, using partial first records, were of the order of 0.30 and 0.34 for 100- and 200-day yields, respectively. For percentage of butterfat, the values were 0.44 and 0.63, respectively. Repeatability values were 0.47 for milk, 0.45 for butterfat, and 0.68 for percentage of butterfat. Herds, sires, and cows in sire accounted for 25, 14, and 21%, respectively, of the total variance in milk yield.

In selecting for production traits in Brown Swiss cattle, first records appear to be as valuable as any other single record or average of records. Partial first records of 100 or 200 days in length will be almost as effective in improving milk and fat yield as selection based on 305-day first records.

The heritability estimates found in this study of Brown Swiss cattle are slightly higher than those previously reported for production traits in other breeds of dairy cattle in the United States. However, most of the previously reported estimates fall within the lower range of the fiducial limits reported here.

¹ These data are part of a thesis presented by the senior author to the University of Wisconsin in partial fulfillment of the requirements of the degree of Doctor of Philosophy.

² Approved for publication by the Director of the Experiment Station, University of Wisconsin, Madison.

³ Data provided by the Brown Swiss Cattle Breeders Association, Beloit, Wisconsin.

⁴ Present address: Department of Dairy, Michigan State University, East Lansing, Mich.