Cross Breeding in Dairy Cattle: The Effect on Calving Ease

Calving traits for frequently used dairy breeds and crossbreeds were investigated using calving records collected in Australia over a period of 18 years. Dystocia (calving difficulty) was highest for heifers calving to Holstein-Friesian bulls, and Jersey calves caused the least dystocia. Incidence of dystocia in Holsteins was influenced by the season (gestation lengths were longer in winter, resulting in larger calves and more dystocia) and by the age of the cow, but these effects were less noticeable in Jersey cross calvings and there was no significant difference between calving months, sexes or cow ages for dystocia in Jersey calves. Logit transformation of proportion suffering dystocia reduced, but failed to eliminate, these significant breed interactions. Though there was a major breed difference for calving ease between Jersey and Holstein-Friesian bulls, the bull standard deviations of the two breeds for this trait were sufficiently large, relative to the breed differences, that there will be a small percentage of Holstein-Friesian bulls that may be as easy calving as many Jersey bulls.