N. Ghavi Hossein-Zadeh - Department of Animal Science, Faculty of Agriculture, University of Guilan, Islamic Republic of Iran

Calving records from April ۱۹۹۸ to September ۲۰۰۶ comprising ۱۰۴,۵۷۲ calving events from ۱۶ dairy herds of Iran were used to analyze the potential effect of dystocia on calf stillbirth and productive traits in Iranian Holsteins. Statistical analyses of production traits were performed using a linear mixed model procedure. Also, a logistic regression model was constructed to analyze the effect of dystocia on calf stillbirth. The odds of stillbirth was greater after severe dystocia [P< ۰.۰۰۱; Odds Ratio (OR)= ۲۹.۶۶]. Also, the odds of stillbirth were the highest for primiparous cows which calved with severe dystocia (caesarian). Cows that experienced caesarian at calving had the lower ۳۰۵-day milk yield than other classes of dystocia (P< ۰.۰۵). Cows that experienced caesarian at calving had the lower unadjusted, ۳۰۵-day and mature equivalent fat yields than other classes of dystocia (P< ۰.۰۵). The results of this study indicated the scope of economic and animal welfare opportunities associated with the reduction of dystocia by management and breeding in dairy herds.

Calving difficulty, Dairy cow, Milk yield, mortality