Analysis of Management Traits in the New Zealand Dairy Cattle Population

Dairy farm profitability is influenced by the production and non-production traits of the cows. In New Zealand (NZ), cows in Livestock Improvement’s Sire Proving Scheme (SPS) herds are measured for 17 nonproduction traits known as traits other than production (TOP). Four of these traits are scored by the farmer and are considered to be management traits. The remaining 13 traits are scored by inspectors and related to conformation characteristics of the cow. Scoring for all TOP is done on a linear scale from 1 to 9. The national selection index introduced in 1996 (Harris et al., 1996) included the breeding values (BV’s) for milk, fat, and protein yields, live weight, and survival. Survival was measured as binary traits from lactations 1 to 2, 2 to 3, 3 to 4 and 4 to 5, with each resulting BV weighted by its economic value. As part of a project to enhance the survival BV, research was undertaken to determine the associations between the TOP and survival, with a view to determining whether the accuracy of the prediction of survival BV could be enhanced using information on these traits. Associations between the TOP and survival traits were assessed using two methodologies. Linear model methodology was used to estimate genetic and phenotypic correlations between the TOP and survival for each lactation. This work is a continuation of the work initiated by Cue et al. (1996) with six additional years of data and inclusion of survival up to the fifth lactation. Survival analysis (see, for example, Klein and Moeschberger, 1997) was used to examine the degree to which the TOP influenced longevity measured as days of age from first calving to last known herd test. Results for the linear model analysis and survival analysis are reported for the four management and four conformation traits. The four conformation traits chosen were the ones with the highest genetic correlations with survival up to the 5 lactation.