The objective of the present study was to determine the possibility to improve the reproductive performance of buffalo cows through the continuous exposure to bull with grazing and free-stall housing management. Sixty-four Egyptian multiparous buffalo cows raised under two different management systems in two farms were used in this study. The cows in the first farm (management system 1, MS 1) were loose-housed in a free-stall yard, grazed for 4 h per day, suckled their calves for 2-3 months and were continuously exposed to a fertile bull. The cows in the second farm (management system 2, MS2) were confined in an open-fronted tie-stall shed, not grazed, suckled their calves for only 7 days and were exposed to a fertile bull twice per day (30 min per session). All the cows were fed a diet of green berseem (Trifolium alexandrinum), rice straw and concentrates to meet their maintenance and production requirements. The cows during both the treatments were milked twice per day after weaning. The cows in both groups were between the second and the sixth parity, weighed 450-480 kg and had average daily milk yields of 5.0-6.0 kg. In each farm, cows were visually checked twice daily at 07:00 and 17:00 h for the signs of oestrus and animals proved standing heat were naturally mated. Rectal palpation was used to monitor uterine involution and for pregnancy diagnosis. Blood was sampled twice per week from 7 to 150 days post-partum for serum progesterone assay. The results revealed that post-partum intervals to each of first ovulation, first oestrus, conception and next parturition were significantly (P < 0.05) shorter in MS1 group than in MS2 group. In the meantime, MS1 increased (P < 0.01) the conception and calving rates by 21 and 25%, respectively compared to MS2. Percentages of post-partum cyclic animals and animals exhibiting ovulatory oestrus were greater (P < 0.01) in MS1 group than in MS2 group. However, the percentage of animals cycling before day 60 post-partum was significantly (P < 0.01) lower in MS1 group than in MS2 group (13% versus 28%). By day 120 post-partum, only 63% of the buffaloes were cycling in MS2 group versus 94% in MS1 group. Percentage of silent ovulation was insignificantly higher in MS2 group (34%) than in MS1 group (25%). However, the percentage of false oestrus was higher (P < 0.01) in MS1 group than in MS2 group (16% versus 3%). In addition, percentage of short ovulatory cycles (15-17 days) was greater (P < 0.01) in MS1 group than in MS2 group, whereas percentage of long ovulatory cycle (25-28 days) was higher (P < 0.01) in MS2 group than in MS1 group. It was concluded that continuous exposure of buffalo cows to a fertile bull with grazing management under free-stall housing system enhances resumption of post-partum ovarian activity and improves conception and calving rates. (C) 2002 Elsevier Science B.V. All rights reserved.
