Reproductive responses of Sarda ewe lambs treated for oestrus induction and synchronization during non-breeding season

This thesis is the result of studies concerning the reproductive responses of Sarda breed ewes undergo different techniques for induction and synchronization of oestrus during non-breeding season. A combination of pharmacological techniques (with use of progestagens plus gonadotrophins) and management techniques like the ''male effect'' was evaluated. Similar results in oestrus incidence and fertility were obtained after using intravaginal sponges containing 40 mg of fluorogestone acetate (FGA) for 9, 12 or 14 days. In this regard, similar results were obtained after using different doses of Pregnant Mare Serum Gonadotrophin (PMSG) injected at the moment of sponge withdrawal. A single administration of 35 mg of natural Progesterone (P4 priming) associated with PMSG did not seem to induce oestrus behaviour or affect the sexual activity and pregnancy rate of the ewe lambs during nonbreeding season. Similarly, also the ''ram effect'' did not seem to have any influence on the pregnancy rate and ovarian activity when used singly in ewe lambs. Considering early pregnancy diagnosis and ovarian activity evaluation, transrectal ultrasound method proved to be practicable in field conditions without previous fast or water restriction in Sarda ewe lambs. Considering adult, multiparous and lactating Sarda ewes, a single administration of 33 mg of natural Progesterone (P4 priming) plus PMSG before the introduction of the rams concentrated oestrus 17 to 22 days later and enhanced pregnancy rates.