Estimation of Genetic Trends and Correlations for Jersey Cattle

Abstract

Genetic correlations were estimated between sire evaluations for 14 type traits, 4 production traits, and stayability to 36, 48, 60 and 72 mo. of age from type information and 469,460 lactation records on daughters of 3789 Jersey sires. Most correlated genetically with stayability were production traits with estimates that ranged from 0.44-1.01. Of the stayability measures, stayability at 48 mo. of age had the highest correlation with production and other stayability measures. Modified Contemporary Comparison and Northeast Artificial Insemination Sire Comparison sire evaluations on daughter records had correlations of 0.77 and 0.71 for milk and fat. The Northeast Artificial Insemination Sire Comparison was correlated with stayability; the Modified Contemporary Comparison was correlated with type evaluations. Estimates of yearly genetic means indicate substantial improvement in recent years for production and stayability. Animals freshening from 1969-1977 have improved 290 kg of milk, 10.5 kg of fat, and 1.3, 4.0, 4.5 and 3.1 units of stayability for 36-, 48-, 60- and 72-mo. stayability because of improved sires only. This is an annual improvement due to sires of 36 kg of milk, 1.3 kg of fat, and 0.2, 0.6, 0.8 and 0.6 units of stayability.