Three Mating Systems Compared: I. First-, Second-, and Third-Lactation Milk Yields, Composition, Flow, and Milking Times

Abstract

Outcrossing, mild inbreeding, and crossbreeding in a common foundation of Holstein cows were compared in the Beltsville herd from 1957 through 1970. The outcross and mildly inbred systems consisted of four generations, and the crossbred system consisted of two- and three-breed crosses plus the Holstein backcrosses on the three-breed crosses. Sires for the outcross system were selected from among Holstein bulls in artificial insemination. Sires for the mildly inbred system were selected from bulls born in the Beltsville herd with daughters in other herds. Sires for the crossbred system were selected from Brown Swiss and Ayrshire bulls in artificial insemination and some of the Holstein bulls from the outcross system. All sires were selected on yield of milk of their daughters in other herds. Cows in the outcross system outproduced cows in the other two systems by 275 and 429kg of milk, 18 and 3kg of fat, 27 and 29kg of solids-not-fat and 11 and 7kg of protein. Cows in the crossbred system were .1 to .4% higher in percentage of components. Within the crossbred system, decreasing Holstein blood was associated with lower yield and higher percentages whereas the backcrosses were nearly equivalent to the Holstein outcrosses. Differences among generations within the outcross and mild inbred systems were small for traits of yield and components of milk. Differences among the three systems in two traits of rate of milking ranked as for milk yield.