Evaluation of reproductive performance in lactating dairy cows with prostaglandin F2α, gonadotropin-releasing hormone, and timed artificial insemination

Abstract

Nine hundred and twenty Holstein cows from 16 commercial dairy herds to evaluate three systematic breeding protocols: 14-d PGF2α, timed artificial insemination (AI), and GnRH-PGF2α, relative to AI following estrus detection without hormone intervention. The timed AI protocol involved GnRH, followed by PGF2α 7 d later and GnRH again 2 d after PGF2α, with AI 6 to 18 h after the second GnRH. The GnRH-PGF2α protocol consisted of GnRH followed by PGF2α, 7 d later. Eight herds relied on visual observation to detect estrus, and eight herds utilized the HeatWatch estrus detection system. The average interval to first postpartum AI was shortest for the timed AI protocol (77.1 d) followed by the 14-d PGF2α protocol (81.6 d). There was no difference in days to first AI between the control (86.1 d) and GnRH-PGF2α (89.5 d) protocols. Percent pregnant per first AI did not differ among control (45.6%), 14-d PGF2α (43.7%), or GnRH-PGF2α, (44.0%) protocols, but all protocols had a higher percent pregnant per first AI than the timed AI protocol (30.1%). Response to the GnRH-PGF2α protocol was limited because 44.0% of the cows submitted to the protocol were not detected in estrus ≤10 d post-PGF2α administration and had an interval to first AI of 103.8 d. Cumulative percent pregnant by 120 d postpartum did not differ between control cows (53.1%) and hormonally treated cows (50.6%). Visual observation herds had a shorter interval to first post-partum AI (82.8 d) than the HeatWatch herds (84.8 d), with a higher overall rate of estrus detection across all protocols (75.3 and 67.6%, respectively).