Non-genetic factors affecting dystocia and its effects on milk production of Holstein dairy cows in Morocco

摘要

The objective of this study was to analyze the effects of non-genetic factors affecting calving difficulty and to investigate the effect of dystocia on 305-day milk and fat yields and fat percent of Holstein cows in North of Morocco. The data set consisted of 1770 calving records for the period from July 2008 to December 2012. Calvings were visually scored on a 5-point system of difficulty with increments of 1. Factors influencing dystocia were analyzed using gamma regression in the GENMOD procedure. The average incidence of dystocia was 4.24%. Dystocia was significantly influenced by calving year and birth number/sex combination (P0.001), but not significantly affected neither by parity nor calving season (P0.05). Parturitions that occurred in 2008 were associated with more calving difficulty than those occurring during other calving years, with a decreasing trend of dystocia from one year to the other. The least-squares means of dystocia scores decreased from 1.92 in 2008 to 1.32 in 2012. Calving difficulty was significantly influenced by birth number/sex of offspring (P0.001). Cows giving birth to single males had a probability of dystocia higher than dams of single females. The least-squares means for scores of dystocia were 1.40 and 1.33, respectively. Moreover, dystocia was significantly influenced by birth number. Thus, the probability of dystocia was higher in cows giving birth to twins than in those with singles. However, the Chi-Square tests indicated that the differences among dams giving birth to twin females, twin males and twin female and male were not significantly different (P0.05). The 305-day milk yield, fat yield and fat percent were not significantly affected by dystocia (P0.05) although cows with dystocia produced 182.8 kg, 7.4 kg and 0% less than cows without dystocia, respectively.