---

Calving records of Iranian buffaloes from April 1991 to June 2010 comprising 1,151 herds with 34,911 calving events were used to evaluate reported secondary sex ratio, stillbirth, and calf birth weight. Logistic regression models were applied to analyze stillbirth and calf sex at birth, and statistical analysis of calf birth weight was performed using a linear mixed model. Overall, the ratio of males to females was 53:47. It was observed that there were no significant effects of herd, calving year, season of calving, dam parity or interactions between these effects on the odds of male or female rates in Iranian buffaloes. Greater odds of calf stillbirth existed for calves born from primiparous buffaloes than from multiparous ones (Odds Ratio (OR)= 1.83; P< 0.0001). The greatest odds of stillbirth was for spring season (OR= 2.47; P< 0.0001), and male births had greater odds of stillbirth than female ones in Iranian buffaloes (OR= 1.21; P< 0.01). In general, male calves were heavier than the female calves at birth (P< 0.01) and the birth weights of calves from cows of parity 4 and beyond were significantly more than the weights of calves from cows of other parities (P< 0.01). Fall-born calves had significantly greater body weight at birth than calves born in other seasons (P< 0.01). It seems that providing good management practices for primiparous and multiparous buffaloes to minimize stress before parturition can reduce stillbirth incidence.

---

 Calving records from April 1998 to September 2006 comprising 104,572 calving events from 16 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< 0.001; Odds Ratio (OR)= 29.66]. 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 305-day milk yield than other classes of dystocia (P< 0.05). Cows that experienced caesarian at calving had the lower unadjusted, 305-day and mature equivalent fat yields than other classes of dystocia (P< 0.05). 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.

---

The objective of this study was to estimate Daughter Yield Deviations (DYDs) of bulls and Yield Deviations (YDs) for cows using a random regression model and validation of genetic trend using estimated DYDs and Method II of Interbull for test-day records of Somatic Cell Score (SCS) in the first lactation of Iranian Holsteins. Data set included the 108995 test day records collected by the Animal Breeding Center of Iran from 2001 to 2010. Results of the present study indicated that variation in YDs of cows at different stages of lactation corresponds closely with their Estimated Breeding Values (EBVs). Because YDs and DYDs are considered as an additional measure of an animal’s genetic merit, their correlation with EBVs is very important. The correlation between DYDs and EBVs of bulls for SCS was 0.88. High correlation estimates between DYDs and EBVs indicated that, in addition to EBV, the DYD can be an appropriate measure for dairy cattle breeding programs. The correlation increased with increase in the number of bull daughters and the average number of test-days of daughters. Estimated DYDs for each production year were used to validate the genetic trend obtained from the model which was used for genetic evaluation. Results indicated that genetic trend for SCS in the first lactation of Iranian Holsteins was slightly overestimated.