Is Crossbreeding the Answer to Questions of Dairy Breed Utilization?

Abstract

The current interest in crossbreeding in the commer- cial dairy industry, even though it is quite limited, raises questions of breed utilization. Fewer than 5% of US dairy cattle are other than purebred or grade Holsteins.ThelargeadvantageofHolsteinsforadditive genetic merit for lactation milk yield is apparently re- sponsible for this trend. Why, then, this interest in crossbreeding? The economic importance of traits such as reproduction, health, and survival in dairy produc- tion systems is likely the basis for the interest in cross- breeding, even though these traits are secondary to milk yield. Several US studies and a Canadian study confirmed that while several crossbred groups were equivalent to Holsteins for lactation milk yield, none were superior. Two crossbred groups in the Canadian study had lifetime yields, milk value, and net returns equivalent to Holsteins. In the New Zealand study, Friesian-Jersey reciprocal crossbreds were predicted to exceed Friesians in first-lactation fat yield. Crossbred performance is dictated by a combination of additive and nonadditive genetic effects. Evidence exists for di- rect, maternal, heterosis, and cytoplasmic maternal ef- fects.Heterosisof15to20%forlifetimetraitswasfound in two studies. Results from previous crossbreeding studies have something to recommend for inclusion of Holstein, Ayrshire, Brown Swiss, and Jersey breeds in a crossbreeding scheme. However, multiple-generation lifetime performance on an array of purebreds and crossbreds under US condition does not exist. Full unique identification of individual animals, including breed composition, would permit the use of DHIA data to estimate additive and nonadditive genetic parame- ters for the traits recorded therein. Survival data from birth and health data would need to be fully recorded