Large dairy herds reproduction management under Moroccan conditions. II. Resumption of ovarian cyclicity post-partum

Abstract

The present study was performed on 158 Holstein cows reared among two dairy herds. lts aim is evaluation during the shorter days of the year (September to March) of the mean interval between calving and resumption of ovarian cycle, estimated either from estrus behavior or from increase of plasma concentration of progesterone. The simple oestrus observation alone revealed its inadequacy to the onset delay. By contrast, the evaluation of plasma concentration of progesterone from cumulative data revealed that 50 % of the females present an onset of their cycle at day 30 post-partum and 90 % at day 60. Hence the majority of the anoestrous cows during the second and third month post-partum were in true anoestrus for 10 % approximately. Daily milk production has exerted a significant influence on the mean calving-cyclicity interval, but neither the post­ partum weight variation (assessed through girth measurement) nor uterine infection did so. The calving-oestrus detection interval does influence the number of days open but the calving to cyclic resumption interval did not. To conclude, under Moroccan environmental conditions in shorter days, the ovarian physiology of dairy cows was not different from what has been reported under temperate climate. However, oestrus detection remains a major problem and a critical limiting factor to a better economic income for Moroccan dairy herds.