Growth and Production of Inbred and Outbred Holstein-Friesian Cattle

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Abstract
Growth and production data were obtained on inbred and outbred progeny of Holstein-Friesian sires in 3 Wisconsin State Dept. of Public Welfare herds. The avg. intra-sire partial regressions (holding mature size of dam constant) of 4 body dimensions (height at withers, circumference of shin bone, heart girth and width of hips) on inbreeding percentage were used to measure the effect of inbreeding on body size at 6 and 18 mos. of age and at maturity. These partial regressions were essentially zero except for heart girth at 18 mos. and maturity, but the decrease in heart girth was significant only at 18 mos. The intra-sire partial regressions (holding dam''s production constant) of milk and butterfat production of 42 inbred and 47 outbred cows on inbreeding were significant. There was an avg. decrease of 74 lbs. of milk and 2.3 lbs. of butterfat for each 1% increase in inbreeding. There was no evidence of an effect of inbreeding on butterfat percentage. Considerable differences were observed in the partial regressions for the sires, indicating that offspring of some sires could be inbred without any apparent decrease in body size or production.