The use of estrus synchronization has many benefits. The timing and length of the breeding season is directly related to the timing and length of the lambing season. A more concise breeding season will result in a more concise subsequent lambing season. This can improve labor efficiency (minimize the number of nights you have to check the barn), improve uniformity of the lamb crop, increase average age and weight of the lamb crop, and allow for more grafting opportunities if needed. Additionally, if we know within a few days when the majority of lambs will be born, we can better time the start of late gestation supplementation, vaccination, and availability of labor resources reducing input costs. One thing to consider is the requirement for additional jugs if shed lambing as a greater portion of your flock will lamb in a tighter window of time.
Many synchronization protocols exist but if natural cover is being utilized, a simple 10-day CIDR protocol without any additional injections can be very successful, especially within the normal breeding season. Even during spring breeding (April), we have used this protocol with reasonable success. On average, ewes will mark 1-3 days after CIDR removal.
We can use the Katahdin flocks at our Small Ruminant Educational Unit (SREU) and Upper Piedmont Research Station (UPRS) as an example. This past fall, rams were turned in on the same day at both locations and all ewes were bred on pasture with similar supplementation for flushing. At UPRS, ewes were synchronized using a 10–12-day CIDR protocol. Beginning on day 10 after CIDR insertion, five CIDRs per breeding group per day were removed. With two breeding groups and 30 ewes, it took three days to remove all CIDRs. No injections were given. Rams were introduced to breeding groups when CIDR removal began. At the SREU, no synchronization was utilized. Final mark dates were recorded for each ewe to determine which heat cycle they conceived in. Results are shown below.
By using a synchronization protocol, over 80% of the ewes bred in Week 1 and subsequently lambed in Week 1 resulting in a large group of consistent lambs born early in the season. After a couple weeks of rest for the shepherd, the last few ewes lambed and the lambing season was over. In contrast, without synchronization, the SREU lambing season was more drawn-out with more consistent distribution of lambing events. On average, there was a 7-day difference in average mark dates between the groups in favor of the synchronization group. Additionally, with the synchronization protocol, the total length of the breeding season was only 28 days and all ewes had at least two heat cycles to be bred. This is just one-year’s example but illustrates the potential benefit of using a relatively simple CIDR protocol for estrus synchronization to reduce the length of the breeding and lambing seasons.
By: Dr. Andrew Weaver, NCSU Small Ruminant Specialist
