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Growth and Production of Inbred and Outbred Holstein-Friesian Cattle¹

University of Wisconsin, Madison

ABSTRACT

Growth and production data of inbred and outbred progeny of Holstein-Friesian sires in three Wisconsin State Department of Public Welfare herds were collected and analyzed to determine the effect of inbreeding on body dimensions (height at withers, circumference of shin bone, heart girth and width of hips) at 6 and 18 months of age and at maturity and on milk and butterfat production and butterfat test. The average intra-sire partial regression (holding mature size of dam constant) of dimension on inbreeding was used to measure this effect. The partial regression of dimensions on inbreeding was essentially zero, except for heart girth at 18 months and maturity, which was significant only at 18 months. Intra-sire partial regressions (holding dam's record constant) of milk and butterfat production of 42 inbred and 47 outbred cows on inbreeding were significant and amounted to an average decrease of 74 lb. of milk and 2.3 lb. of butterfat for each 1 per cent increase in inbreeding. No evidence of an effect of inbreeding on butterfat percentage was indicated.

Considerable variation was found in the partial regression coefficients of sires, indicating that offspring of some sires could be inbred without any apparent decrease in body size or production, possibly in part because the beneficial effect of increasing the relationship to a sire transmitting a superior level of production tends to offset detrimental effects of inbreeding to him.

¹ Paper No. 376 from the Department of Genetics, Agricultural Experiment Station, University of Wisconsin.

² Assistant Professor, Dairy Husbandry Department, West Virginia University.

³ Associate Professor, Animal Husbandry Department, University of Missouri.