RESUMEN
This prospective longitudinal study deals with the associations between digital disorders and reproduction indices in dairy cattle on a farm in the vicinity of Tehran. It was carried out on 225 postparturient Holstein heifers. The evaluation of lameness due to digital disorders on postpartum period of heifers were done and after diagnosis of lameness [based on a 5 points lameness scoring system], the digital lesions and reproduction data of lame cows were recorded in a pre-established questionnaire and comparison with reproduction indices of other healthy heifers were made statistically using Chi Square and Student "t" tests and the relative risk "R.R." for each of indices was calculated and 95% confidence interval was made. Seventy-six cows among 225 cows were diagnosed lame in the period of study [30 months]. Digital dermatitis [28.9%] and Sole ulcer [21.2%] were the most prevalent lesions. All reproduction indices in this study including Projected minimum average days open, Days to first service, Projected minimum calving interval, Days in milk, Services per pregnancy for all cows, Services per pregnancy for pregnant cows, Conception rate at first service and Overall conception rate were found significantly different between lame and control groups [p < 0.0005]. 95% confidence interval for R.R. indicated that in lame cows the relative risk of negative rates of reproduction indices are significantly higher than non lame cows. It was concluded that pain and stress due to digital lesions play a key role in suppressing observable behavioral estrus which follows to negative changes of reproduction indices and other undesired consequences. On the other hand, pain may also suppress feeding and ruminating functions, leading to negative energy and protein balances and a low Body Condition Score [BCS] specifically in postpartum period. Thus, in order to mitigate the undesired effects of lameness on reproductive system and reproduction performance, early diagnosis and treatment of digital lesions is needed to be established