Effect of PRID treatment on conception rate in mediterranean buffalo heifers

To evaluate the possibility to control oestrus in cycling buffalo heifers and induce fertile oestrus in prepuberal ones using a PRID in order to breed them during the low breeding season (March-June period), 79 buffalo heifers in two different farms (TM: n = 39; IM: n = 40) were used. In each farm, the animals were assigned (n = 19-20/group) to either group A ( less than or equal to 20 months) or group B ( > 20 months). In March, all heifers of group A, except one, were non-cycling while, in group B, all heifers of the TM and 20% of the IM farm were cycling. Within age group, 10 animals, regardless of cyclicity, received a PRID for 10 days plus PMSG on the 7th day, were inseminated (AI) using frozen-thawed semen at 48 and 72 h after PRID removal and then naturally mated at the oestrus following AI; the other heifers, kept with a bull and naturally mated, were used as controls. Pregnancy was diagnosed by rectal palpation 40 and 60 days after AI and every month during a subsequent S-month period of natural mating. PRID was useful in inducing oestrus in non-cycling animals (80.0% in TM and 94.4% in IM) and in synchronising the cycle (in oestrus within 72 h of PRID removal, 85.0% in TM and 80.0% in IM). The conception rate (CR) was similar in both farms. In group A, CR in treated animals was 50% in TM and 30% in IM after AI; when including the remaining trial period (AI + natural mating in treated; natural mating in controls), CR was 50% in treated animals, while it was 5% in controls. In group B, CR in treated animals was 35% after AI; when including the remaining trial period, CR was 80% in treated animals, and 53% in controls. PRID plus PMSG treatment of heifers could have an economic impact on buffalo production because a greater proportion of heifers could be bred early. Moreover, with this treatment, it is possible to synchronise oestrus in cycling heifers, overcoming the problem of oestrous detection and increasing the effectiveness of Al programmes in buffalo heifers. (C) 2001 Elsevier Science B.V. All rights reserved.