The use of progesterone intravaginal devices is superior to use of the ram effect at hastening the reproductive performance in transitional Targhee ewes

To compare the use of controlled intravaginal drug release (CIDR, EAZI-BREED™ CIDR® Sheep, USA, Zoetis) with the ram effect, a combination of CIDR and ram effect and the addition of P.G.600® to each of these scenarios on their contribution to inducing the onset of cyclicity and their ability to improve reproductive efficiency in a commercial sheep flock, a randomized clinical trial was conducted. Multiparous ewes (n = 283) were randomly assigned to one of six treatments prior to intact male introduction on day 0: only CIDR devices (day −5 to day 0) (n = 40), exposure to two vasectomized rams (d-14 to d0) (n = 55), CIDR (d-5 to d0) and an intramuscular injection of P.G.600® (d0) (n = 40), exposure to two vasectomized rams (d-14 to d0) and treated with CIDR devices (day −5 to day 0) (n = 40). exposure to vasectomized rams (d-14 to d0), CIDR (d-5 to d0) and an intramuscular injection ofP.G.600®, (d0) (n = 38), and a control group, without exposure to vasectomized rams, CIDRs or P.G.600® (n = 70). Ewes were exposed to intact males on day 0. Days to lambing from the earliest expected lambing date at 150 days post introduction of rams was compared between groups with survival analysis. The mean survival time was significantly shorter in all groups that used CIDR compared to the control group (P