International Journal of Dairy Science1811-97431811-9751Asian Network for Scientific Information10.3923/ijds.2007.85.89-LariMaryam Ansari 1200721To determine the perinatal calf mortality in the region and to study some of contributing factors, a retrospective survey was conducted in the Fars province, southern Iran. Using monthly report of 64 registered dairy herds, data about births since September 2003 to December 2004 was obtained from the Agricultural Jihad Organization of the province including parity of dam, dystocia, sex of calves, and it's survival up to one hour of birth. Dystocia was recorded as birth without assistance, with one assistant, with two assistants and with jack. Mortality rate was calculated as proportion of died calves to all births. According to number of dairy cows, study herds were categorized as less than 50 heads, 50-100 heads and more than 100 heads. Statistical analysis was done by Chi-square test, Fisher's exact test and logistic regression. The mortality rate was 3.5%. There was no significant association between parity of dam, sex of calf and season of calving with mortality. Overall dystocia rate was 9.8% with significantly highest level in heifers (p<0.001). There was strong association between degree of dystocia and mortality rate. Odds of death was 4 times in calving with one assistant (OR = 4.26, 95% CI: 1.5-11.4) and 44 times (OR = 44.5, 95% CI: 14.5-136.1) in pull with jack compared to calving without assistance. In difficult calving, there was significant trend for mortality to increase with parity (p = 0.008). Herd size had no effect on calf mortality however larger herds had significantly higher level of dystocia (p<0.001). According to this study, difficult calving is the most important factor affecting the calf mortality. Also, heifers are at greatest risk due to high level of dystocia. However, when calving is difficult, multiparous dams have more risk for calf death compared with heifers.]]>Azzam, S.M., J.E. Kinder, M.K. Nielsen, L.A. Werth, K.E. Gregory, L.V. Cundiff and R.M. Koch,199371282290Berger, P.J., A.C. Cubas, K.J. Kochler and M.H. Healey,19927017751786Berglund, B., L. Steinbock and M. Elvander,200344110120Curtis, C.R., H.N. Erb, C.J. Sniffen, R.D. Smith and P.A. Powers et al.,1983183559561Erf, D.F., L.B. Hansen and R.R. Neitzel,19907311301134Johanson, J.M. and P.J. Berger,20038637453755Martinez, M.L., A.E. Freeman and P.J. Berger,19836624002407McDermott, J.J., O.B. Allen, S.W. Martin and D.M. Alves,1992564755Meyer, C.L., P.J. Berger, K.J. Koehler, J.R. Thompson and C.G. Sattler,200184515523Nix, J.M., J.C. Spitzer, L.W. Grimes, J.L. Burns and B.B. Plyler,19984915151523Radostits, O.M.,20013rd Edn.,pp: 492-499pp: 492-499Rao, M.K. and R. Nagarcenkar,198012137144Wittum, T.E., M.D. Salmon, K.G. Odde, R.G. Mortimer and M.E. King,1993203232236