American Research Journal of Agriculture

The experiment was conducted with cattle production in North Kordofan, which was closely monitored through a period of 365 days. Seven groups of cattle herders were selected randomly. The recently calved cows were monitored till next conception following post-partum ovarian activity using milk progesterone radioimmunoassay. Days to conception were taken as non-return to oestrus. Regression analyses were done for days to first progesterone rise and days to conception against season of calving and type of breed and correlation between them and body weight and milk yield. The results revealed that there was a wide variation in both days to first ovulation and days to conception. Dry season showed an adverse effect on fertility compared with the rainy season. Cows that had been calved during wet season showed delayed post-partum activity and days to conception with longest days to resumption of ovarian activity showed in dry season (87.66±52.25). The interval to conception was longest in dry season (149.60±69.52 days) and lowest in wet season (113.00±73.80 days) with higher conception rate. Regression analyses showed significant negative correlation obtained during the wet season between days to progesterone rise and body weight at calving, milk yield, Similary days to conception were found to decrease by 38 days for each increase of 1 kg milk yield at 60 and 90 days. Cross breeds, had longer days to ovulation and days to conception compared with local ones, but showed lower pregnancy rates. Local breed showed lowered days to reproductive parameters studied during wet season compared with dry season. Also local breed showed weak negative correlation between days 1st P4 rise and body weight at calving and Milk yield with decline in days. Significant negative correlation were obtained between days to conception and milk yield with corresponding decrease in days for each increase in 1 kg of milk yield. It could be concluded that, poor reproductive performance in cows kept under extensive traditional system was due to poor management practices, which ignored high-energy supplementation during late pregnancy and early lactation, especially during the dry season. Improving feeding strategies may greatly enhance reproductive performance of cows kept under extensive systems of management.