Livability of Purebred vs. Crossbred Dairy Cattle

Abstract

The data for this study were obtained from the Illinois Dairy Cattle Crossbreeding Project. Only those causes of death were included in the analysis which were considered to reflect on the viability, or to show a possible sign of weakness of a breed group. Deaths due to ingesting hardware and poisoning were excluded. Significant differences in livability between the purebreds and the crossbreds or 3~-breds were found in firstgeneration heifers from birth to 1 yr. of age and cows over all lactations~ and in secondgeneration heifers from birth to 1 yr. of age and from birth to calving age. In each of these cases, over twice as many purebreds were lost from the herds as crossbreds or eriss-crosses. The over-all death losses in both generations were 32.7% for purebreds and 13.4% for the crossbreds and 3~-breds. The mean milk production of the live vs. dead cows in each breed group of the first generation was analyzed by the method of least squares. A small and nonsignificant difference was found between the production of the live and dead animals when considered over all animals regardless of breed, by breed of sire, by breed of dam, or by system of mating (purebreeding vs. crossbreeding). This indicates that there is little genetic relationship between livability and productive level and emphasizes the importance of improving the livability characteristics of dairy animals, so that more discretion can be exercised by the dairyman in culling cows. Most studies have indicated only a small or no influence of additive genetic variation on livability characteristics and, therefore, little chance of improving these characteristics by mass selection. However, this study indicates a considerable influence of nonadditive genetic factors, or heterosis, on livability and that crossbreeding dairy cattle may provide a means for immediate and marked improvement.