Flushing and Synchronization Protocol Impacts on out of Season Breeding in Ewes

• Published in: Journal of animal science 2018-03, Vol.96, p.76-76
• Main Authors: Sheffield, J, Roman, C, Roper, B L, Poole, R K, Pickworth, C L
• Format: Article
• Language: English
• Subjects: Animal breeding; Breeding; Breeding of animals; Data processing; Estrus; Exposure; Feeding; Feeds; Fertility; Fetuses; Flushing; Grain; Harnesses; Pasture; Pregnancy; Progesterone; Rams; Sheep; Synchronism; Synchronization; Ultrasound
• ISSN: 0021-8812; 1525-3163

Ewes with low BCS (2 on scale of 5) have reduced fertility and decreased conception rates compared to ewes in more ideal BCS (3 to 4). Providing ewes with low BCS an increased feeding rate prior to breeding may help improve BCS and increase fertility and conception rates. The primary objective of the study was to determine if an increased feeding rate of low BCS ewes prior to breeding would improve conception rates and number of lambs conceived. The secondary objective of the study was to determine if extending the length of time of progesterone exposure via 10, 12, or 14 d controlled intravaginal drug releaser (CIDR) during estrus synchronization impacts ewe fertility. The 46 Dorset and Katahdin based crossbred ewes were used in an out-of-season breeding study. The ewes were allocated to 2 treatments: LOW BCS and HIGH BCS (2.09 and 2.55, respectively). Ewes were maintained on pasture and fed a grain-based flushing supplement based on treatment (0.17 kg HIGH and 0.35 kg LOW per ewe a day, respectively) for 42 d. Ewes in each treatment were divided into 4 breeding groups based on breed. On d 42 ewes began an estrus synchronization followed by natural mating. At breeding the mean BCS were 2.7 LOW and 2.9 HIGH (P > 0.10). All rams were fitted with marking harnesses and marks were recorded daily for 42 d. At d 45 post ram removal, ultrasonography was used to determine the pregnancy rate and estimate fetal counts. The data set was analyzed in Proc MIXED of SAS to determine effects of flushing treatment and synchronization protocol. Means were determined to be significant at P < 0.05 and trends at 0.05 < P < 0.10. The conception rates were not affected by BCS at 72.2% for LOW and 71.4% for HIGH (P > 0.10). Fetal counts, however, tended to be lower in LOW compared to HIGH ewes (1.8 and 2.1 ± 0.15, respectively; P = 0.07). It was determined that extended progesterone exposure did not impact conception rates (73, 77, and 64% for 10, 12, and 14 d, respectively; P > 0.10). In addition, fetal counts were similar across synchronization protocols (1.9, 2.0, and 1.9 for 10, 12, and 14 d, respectively; P > 0.10). During out-of-season breeding, using an increased flushing feeding rate in low BCS ewes in conjunction with varying CIDR insertion time during natural mating can promote ewe fertility.