Effect of dietary energy level on physiological responses and reproductive performance of Malpura sheep in the hot semi-arid regions of India

Malpura ewes, approximately 2 years of age and weighing 25.8 kg (N = 16) having lambed 4 months earlier were used to study the effect of feed restriction and re-alimentation on physiological responses and reproductive efficiency. The study was conducted in two phases of 14 weeks with two groups of eight ewes. Ewes were provided a diet consisting of 50% concentrate and 50% roughage ad libitum (Group-1) or placed on a restricted diet i.e. 30% intake of Group-1 (Group-2). The first phasewas in summer followed by the second phase during the start of the monsoon season when all animals have access to natural pasture of Cenchrus ciliaris for 8–10 h daily. Each day at 1600 h all animals were provided fresh water.Weekly observations on respiration rate (breath per min), pulse rate (beat per min) and rectal temperature (◦C) at 0600 and 1400 h were recorded along with body weight. Estrus in ewes was detected with the aid of intact rams of proven vigor at six-hour intervals. Ewes in estrus were hand mated during phase-II following a 14-weeks of re-alimentation period. During the differential feeding (phase-I), Group-1 animals had significantly higher respiration rate and pulse rate at 0600 and 1400 h, respectively, than those of Group-2 animals, whereas rectal temperaturewas similar (P > 0.05). During phase-II, significantly higher values were observed only for respiration rate of ewes in Group-1 compared to Group-2. Animals fed ad libitum maintained their body weights throughout the study period. In contrast, those on a restricted feeding (Group-2) weighed less during phase-I and more during phase-II (P < 0.05). Restricted feeding significantly reduced the duration of estrus (15 h versus 26 h) and increased the estrus interval (31.5 days versus 18.6 days) in phase-I with a tendency to reach its normal value during phase-II. After 14 weeks of re-alimentation, all the animals were hand mated. Animals in Group-1 required less services per conception than those of Group-2 (1.3 mating/ewes versus 1.9 mating/ewes). Again, birth weight of lambs from ewes in Group-1 was significantly higher than those from ewes in Group-2 (3.59 kg versus 3.06 kg). Results indicate that ewes tend to compensate for reproductive losses incurred during the restricted feeding period following access to adequate feed resources but were not consistent with those fed ad libitum. © 2004 Published by Elsevier B.V.