Comparison of purebred and crossbred dairy cattle for Victoria: estimation of genetic effects for yield

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Abstract
The yield performances of pure and crossbred dairy cattle (bred by artificial insemination) were compared using a sample of 253 422 herd-recorded Victorian dairy cattle. Pure breed groups included Holstein-Friesian (HF), Jersey (Jer), Ayrshire (Ayr), Guernsey (Gue) and Australian Illawarra Shorthorn (AIS), although numbers of Ayr, Gue and AIS were very small. The model analysed included breed additive and maternal effects, as well as heterosis and epistatic effects. Sire's Australian Breeding Value and number of generations of A1 breeding were also included. Purebred HF was found to outproduce all other purebred groups for kilograms of fat and litres of milk. Jer produced 14 kg fat (8%) and 850 L milk (22%) per lactation less than HF. Maternal breed had an effect with Jer and Gue dams being superior to HF (and other) dams. Heterosis for yield was of the order of 3% (or 5 kg fat and 110 L milk). There was no evidence of recombination loss in the crossbred groups. After combining estimates of direct, maternal and heterosis effects, HF x Jer, AIS x HF and Ayr x HF (where the first breed is breed of sire) were all found to compare equally or favourably with purebred HF for yield.