EFFECTS OF MATING SYSTEM ON PRODUCTION TRAITS IN DAIRY CATTLE.

Abstract An experiment designed to study the effect of various mating systems on sire-lines of dairy cattle is described. Inbreeding depressions were found in various production traits by comparing outbreds with inbreds (F, ≅ 0.25). The differences were 1,313 lb, 35 lb, 1,761 lb, and 48 lb in favor of the former, in actual milk, actual fat, M.E. milk, and M.E. fat. of the first lactation, respectively. For the same traits, differences of 1,832 lb, 74 lb, 2,455 lb, and 97 lb, respectively, were found in favor of the two-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.

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