Alternatives to improve a prostaglandin-based protocol for timed artificial insemination in sheep.

The objective was to improve the reproductive performance of a prostaglandin (PG) F2-based protocol for timed artificial insemination (TAI) in sheep (Synchrovine®: two doses of 160 g of delprostenate 7 d apart, with TAI 42 h after second dose). Three experiments were performed: Experiment 1) two doses of a PGF2 analogue (delprostenate 80 or 160 g) given 7 d apart; Experiment 2) two PGF2 treatment intervals (7 or 8 d apart) and two times of TAI (42 or 48 h); and Experiment 3) insemination 12 h after estrus detection or TAI with concurrent GnRH. Experiments involved 1131 ewes that received cervical insemination with fresh semen during the breeding season (32/34 °S‐58 °W). Estrous behaviour, conception rate, prolificacy, and fecundity (ultrasonography 30‐40 d), were assessed. In Experiment 1, ewes showing estrus between 25 and 48 h or at 72 h after the second PGF2 did not differ between 80 and 160 g of delprostenate (73 vs 86%, P 0.07; and 92 vs 95%, P NS, respectively). Conception rate and fecundity were lower (P 0.05) using 80 vs 160 g (0.24 vs 0.42, and 0.27 vs 0.47, respectively). In Experiment 2, giving PGF2 7 d apart resulted in higher (P 0.05) rates of conception (0.45 and 0.51) and fecundity (0.49 and 0.53) than treatments 8 d apart (conception: 0.33 and 0.29; fecundity: 0.33 and 0.34) for TAI at 42 and 48 h, respectively. In Experiment 3, rates of conception, prolificacy and fecundity were similar (NS) between Synchrovine® with TAI at 42 h (0.50, 1.13, and 0.56) and AI 12 h after estrus detection (0.47, 1.18, and 0.55), and Synchrovine® plus GnRH at TAI (0.38, 1.28, and 0.49). However, all TAI treatments had lower (P 0.05) prolificacy and fecundity compared to AI following detection of spontaneous estrus (1.39 and 0.83, respectively). In conclusion, the Synchrovine® protocol was: a) more successful using 160 vs 80 g delprostenate; b) more successful wit ha7d than 8 d PGF2 interval; c) similarly effective for TAI versus AI 12 h after estrus detection; and d) not improved by giving GnRH at TAI.