Effects of Mating System on Production Traits in Dairy Cattle

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Abstract
An experiment designed to study the effect of various mating systems on sire-lines of Holstein-Friesian cattle is described. Inbreeding depressions were found in various production traits by comparing outbreds with inbreds (Fx 0.25). The differences were 1313 lb., 35 lb., 1761 lb., and 49 lb. in favor of the former, in actual milk, actual fat, M.E. milk and M.E. fat, of the 1st lactation, respectively. For the same traits, differences of 1832 lb., 74 lb., 2455 lb., and 97 lb., respectively, were found in favor of the 2-line crosses compared to inbreds of the same line. However, inbreeding effects varied significantly among sire-lines. There was no evidence that increase of production with age was more rapid in inbreds than in outbreds.