379 Effect of progesterone infused controlled internal drug releasing (CIDR) device and timing of gonadotropin stimulation using P.G. 600 ® on reproductive success in anestrous ewes

Abstract

Abstract Objective of this study was to determine effects of controlled internal drug releasing (CIDR) devices in combination with P.G. 600 use either at CIDR removal or one day before CIDR removal on day of lambing, lambing rate, and prolificacy in seasonally anestrous ewes. Multiparous ewes (n = 414) were randomly assigned to one of four treatments: untreated (U, n = 122), 7 d CIDR (C, n = 97), 7 d CIDR plus P.G. 600 at CIDR removal (CPG0, n = 97), and 7 d CIDR plus P.G. 600 1 d before CIDR removal (CPG-1, n = 98). Rams (n = 15) were joined with ewes immediately after CIDR removal for a 21 d breeding period. Data collected included day of lambing in the lambing season, lambing rate (number of ewes lambing/ewe exposed), and prolificacy (number of lambs/ewe lambing). Lambing season was further divided into the first 10 d and overall. Lambing rate in the first 10 d was greater (P < 0.05) for CPG0 and CPG-1 ewes compared with CIDR ewes, which was greater (P < 0.0001) compared with U ewes. Overall lambing rate increased (P ≤ 0.0001) in all treatments utilizing CIDR compared with U ewes, but no differences (P > 0.76) due to P.G. 600 were detected. Day of lambing was reduced (P ≤ 0.03) for CPG0 and CPG-1 compared with CIDR ewes, which was reduced (P < 0.0001) compared with U ewes (d 10.6, 9.0, 13.4, and 24.4 ± 0.9 for CPG0, CPG-1, CON, and U, respectively). Prolificacy was similar among all treatments both for the first 10 d of the lambing season (P = 0.86) and overall (P = 0.80). The combination of CIDR and P.G. 600 may be beneficial in promoting fewer days to lambing and increasing overall productivity in out of season breeding scenarios.