Treatments with intravaginal sponges for estrous synchronization in ewes: length of the treatment, amount of medroxyprogesterone, and administration of a long-acting progesterone.

We evaluated if alternative treatments achieve at least similar results as traditional long treatments with intravaginal sponges (IVS) in three experiments considering (1) the use of 6-day treatments associated or not with the administration of PGF2alpha at IVS insertion; (2) a reduction of 50% MAP content in short-term or traditional treatments, with or without change of the IVS 6 days after its insertion; and (3) the substitution of IVS for long-time acting injected progesterone associated with the administration of a PGF2alpha. More ewes came into estrus with long than short IVS treatments, independently of the MAP IVS content. Fewer ewes came into estrus if the IVS containing 30 mg was replaced 6 days after its insertion. The length of the treatment did not affect the conception rate, but the pregnancy rate was greater in 12 than 6 days treatments. The administration of long-acting progesterone did not prevent the lower conception rate associated with the use of PGF2alpha and was less effective to synchronize estrus, but the conception rate did not differ from that of 12d IVS treatments. Overall, MAP content could be decreased without affecting the estrous rate; thereafter, the MAP IVS content should be decreased in the commercial devices. Although pregnancy rate was lower using long-acting injected progesterone than with IVS, as the conception rate did not differ, it is interesting to study deeper the use of this treatment, especially if preparations of progesterone with a longer half-life are developed. However considering all the results, the traditional long IVS treatment still provided the best result.