Oestrus synchronisation in hoggets was compared using either polyurethane sponges containing progestagen or 9 mm diameter silicone elastomer CIDRs (controlled internal drug releasers) in 600 hoggets in 3 trials. CIDRs and sponges were removed after 12 days in late May and 200 IU PMSG given to hoggets in 2 of the trials. Hoggets in the third trial received 0 or 300 IU PMSG. Half of the hoggets were shorn 1 month prior to the 4-day joining with entire rams. The loss rate of CIDRs and sponges was low (2%). No hoggets mated in the first 24 hours after removal and most matings occurred during the second day. During the peak of mating, more CIDR-treated hoggets appeared to mate in 2 trials, but fewer in the third (28 v 44% P<0.01). By the end of the entire joining, there was little difference in total mated. Treatment with CIDRs or sponges did not affect ovarian activity. Pregnancy rates were unaffected by method of synchronisation in 2 trials and improved by CIDRs in the third (38 v 20% P<0.05). Shearing generally had no effect on reproductive performance. PMSG improve oestrous and ovarian activity, but did not affect pregnancy rate. CIDRs were an effective substitute for sponges in achieving synchronised pregnancies in hoggets. Low pregnancy rates limited the ability to fully capitalise on the benefits of synchronisation.
Proceedings of the New Zealand Society of Animal Production, Volume 46, , 209-213, 1986
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