Use of controlled internal drug releasing (CIDR) devices to control reproduction in goats: A review.

High reproductive rates are necessary in order to increase the productivity of goat operations. Progesterone and its analogues are widely used in other species to control the reproductive system to facilitate synchronized births, induce fertile estrus or to facilitate the use of assisted reproductive techniques with the goal of increasing productivity of livestock. Progesterone impregnated controlled internal drug releasing (CIDR) devices are approved for delivery of the natural hormone progesterone to synchronize and induce fertile estrus in sheep. A few studies have reported a high estrous response and pregnancy rates when CIDRs are used to induce estrus in goats. However, significant variation exists in the duration of treatment (5-16 days) and in the use of exogenous gonadotropins as part of the treatment protocol. As gonadotropins are not currently approved for commercial use in small ruminants in the USA, studies are needed to determine the necessity for exogenous gonadotropins and whether they can be replaced by enhancing endogenous secretion through photoperiodic manipulation of the doe and \ or increase stimulation through the 'buck-effect'. Future studies must not only evaluate efficacy, but should consider the economic feasibility of using CIDRs in commercial production systems.

Effectiveness of a short-term treatment with progesterone injections on synchrony of lambing and fertility in tropical hair sheep.

The efficacy of using a low cost system for delivering progesterone as part of an estrous synchronization protocol in sheep was evaluated. In experiment 1, Barbados Black Belly ewes (n=34) and ewe lambs (n=35; 37.5±0.9 kg) were assigned to be untreated, control animals (C), or to receive PGF(2α) on d0 (PG), or receive two injections of progesterone (200mg, i.m. each) on D -5 and on D -2.5, prior to PGF(2α), on D 0 (2PPG). Treatment with 2PPG increased the proportion of animals lambing to the first service (P<0.05), an effect that was greater in ewe lambs than ewes (treatment × parity; P<0.05). The interval from ram introduction to lambing and the mean lambing day was less (P=0.04) in the 2PPG-treated animals compared to control animals. In Experiment 2, lactating ewes from experiment 1 (n=61) 60-85 days postpartum were assigned within parity and number of lambs reared to remain nursing (S; n=29) or weaned (W; n=32) 3 weeks prior to treatment with the 2PPG protocol. There was no effect of treatment on the proportion of animals lambing to the first service or overall, interval from ram introduction to lambing and lambing interval. An 8-month lambing interval was observed in ewes in which estrus was synchronized regardless of physiological state. In conclusion, the two-progesterone injection synchronization protocol may be used as a practical low cost and efficient method of synchronizing estrus to reduce the lambing interval and maximize productivity in tropical breeds of sheep.