The association of level of milk production with reproductive performance in Canadian dairy cattle.

摘要

This thesis describes the association of the level of production with reproductive performance at the herd and animal levels.;At the herd level, each 1000 kg of herd mean mature equivalent milk was associated with an increase of 0.7 points of PR (P .0001). At the individual level, there was a small association of increased milk yield at TD1 with longer time to pregnancy (hazard ratio (HR) = 0.997 per kg, P = .02) and in the same model increasing 305 d projection at TD3 was associated with shorter time to pregnancy (HR = 1.07 per 1000 kg, P 0.0001).;In summary, herd pregnancy rate was significantly higher in higher producing herds, and for individual cows there were significant but conflicting effects of level of production on time to pregnancy. This suggests that managing to provide for high production can be compatible with good reproductive performance.