Combined treatment of eCG and a non-selective inhibitor of phosphodiesterases for enhancing reproductive performance in ewes

Abstract

The aim of this study was to evaluate the effect of the non-selective phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) given concomitantly with eCG on reproductive performance of ewes. In trial 1, eighty ewes were allocated into 8 groups (AC, A1, A2, A3 and DC, D1, D2, D3). Oestruses were synchronized by progestagen sponges. At sponges removal all ewes of A groups received 400 IU of eCG. Concomitantly with eCG, ewes of groups A1, A2 or A3 received IMBX at the dose of 2.5, 5.0 or 25.0 mg, respectively. Ewes of D1, D2 or D3 groups received only IBMX at the same doses, respectively; in each case, ewes of AC or DC groups were controls (C). In trial 2, one hundred eighteen ewes were allocated into 4 groups (BC1, B1 and BC2, B2). Oestruses were synchronized by progestagen sponges. At sponges removal ewes of BC1 or B1 received 200 IU of eCG, while ewes of BC2 or B2 groups received 100 IU. At the same time only ewes of B1 or B2 groups received 2.5 mg IBMX. In both trials, 48 hours after hormonal treatment, ewes were mated. In trial 1, pregnancy or lambing rate did not differ among A or D groups (P > 0.05). Total lambs per ewe were significantly higher in A1 compared to AC, A2, A3 or D1 groups (P < 0.05), but did not differ among D groups (P > 0.05). In trial 2, pregnancy or lambing rate did not differ among B groups (P > 0.05). Total lambs per ewe were significantly higher (P < 0.05) in B1 and B2 compared to BC1 and BC2 groups, respectively. These results indicate that IBMX combined with eCG at the end of an oestrus synchronization treatment improves litter size probably by increasing ovulation rate in ewes. This latter effect seems to be mainly dependent on the amount of gonadotrophins used.