448 The effects of a novel follicle wave and heat synchronization protocol on the follicles, circulating hormones, and estrus of Aanestrous ewes

Abstract

Reproductive performance in seasonally anestrous ewes is poor even after the use of current controlled breeding protocols. Anestrous ewes treated with a medroxyprogesterone acetate sponge, for 12 or 14 d, and estradiol-17β (E2) have synchronized follicular wave emergence. The objective of this study was to determine the effects of an E2 injection 6 d after CIDR insertion on follicles, E2 and LH concentrations, and estrus in seasonally anestrous ewes. Ewes (n = 13) received CIDRs (Day -12) followed by an injection of eCG (500 IU; i.m.; Day 0) at CIDR removal and an injection of sesame oil without (1 mL; i.m.; Control) or with E2 (350µg; i.m.; Day -6) 6 d before CIDR removal. Treatments were balanced for age, parity, and BCS. Blood samples were collected every 6 h for 48 h after E2 injection and every 3 h for 60 h starting 18 h after eCG injection to determine LH concentrations. Blood samples were collected on Day -6 and 0 and every 6 h for 60 h starting 18 h after eCG injection to determine E2 concentrations. Ovarian ultrasonography was done on Day -6 and 0. A ram was introduced on Day 1 to observe estrus. Ewes treated with E2 had higher LH concentrations (0.37 ± 0.05 ng/mL) than ewes treated with oil alone (0.12±0.05 ng/mL) during the 48 h after E2 injection (P < 0.005). Concentrations of LH were highest at 18 h after E2 injection (1.11 ± 0.12 ng/mL; P < 0.001). Ewes treated with E2 had higher LH concentrations (2.10 ± 0.18 ng/mL) than ewes treated with oil alone (0.12 ± 0.16 ng/mL) at 18 h after E2 injection (P < 0.001). The interval from eCG injection to the start of the pre-ovulatory LH surge was similar (37.1 ± 4.4 h; P > 0.05), but was more synchronized in ewes treated with E2 (2.3 ± 0.6 h) than ewes treated with oil alone (12.0 ± 5.1 h; P < 0.01). Concentrations of E2 were similar between treatments on Day -6 (2.1 ± 0.3 pg/mL; P > 0.05) and Day 0 (2.3 ± 0.4 pg/mL; P > 0.05). Concentrations of E2 tended to be highest at 18 h after eCG injection (3.5 ± 0.5 pg/mL; P = 0.076). Maximum follicular diameter was larger on Day 0 (4.8 ± 0.2 mm) than Day -6 (3.4 ± 0.2 mm; P < 0.001). There were no differences in the interval from eCG treatment to the start (37.6 ± 2.7 h) or end (74.7 ± 1.9 h) of estrus (P > 0.05). Adding an E2 treatment during a CIDR-eCG estrus synchronization protocol increased LH concentrations after E2 treatment and stimulated a more synchronized pre-ovulatory LH surge in seasonally anestrous ewes.