Evaluation of non genetic factors affecting milk production traits of Holstein cattle

Abstract

This study was carried out to evaluate the effects of age at calving (AC), parity, days in milk (DIM), calving interval (CI), days open (DO), dry period (DP), number of services per conception (NSC), season of calving on peak milk yield (PMY), time to attain peak milk yield (TPMY), 305 day mature equivalent (305- DMY) and total milk yield (TMY). Age at calving had significant effect (P≤ 0.05) on all traits studied except TPMY. DIM had a highly significant effect (P< 0.001) on PMY (37.14- 39.18 kg), TPMY (99.29- 194.08 days), 305-DMY (8692.86 - 9760.65 kg) and TMY (4552.82- 12416.95 kg) respectively. Furthermore, DO and DP had a highly significant effect on PMY (33.72- 40.29 and 31.81- 41.08 kg, respectively), TPMY (152.01- 165.14 and 139-165 days, respectively), 305-DMY (8613.83- 9606.83 and 7266.76- 9699.76 kg, respectively) and TMY (8057.51- 8865.18 and 6682.97- 8850.30 kg, respectively). NSC had a highly significant effect (P< 0.001) on all traits studied except PMY. On the other hand, parity had no significant influence (P ≥ 0.05) on all traits studied except PMY. CI had no significant effect on all traits studied except 305-DMY. Moreover, season of calving had no significant effect on all traits studied. In conclusion, these factors should be accounted for genetic evaluation process. At farm level, management decisions such as selection and culling, and feeding should made putting these factors into consideration in order to achieve more reliable evaluation results.