Effects of an AI Plastic Sheath with Three Semen Outputs on AI Pregnancy Rates of Beef Heifers Enrolled in Estrus Synchronization Protocols.

We determined whether a newly designed AI plastic sheath with three outputs for semen deposition would reduce semen reflux into the sheath, and increase pregnancy rates of beef females enrolled in estrus synchronization protocols. A total of 881 Angus and Angus crossed beef heifers (13 ± 1.5 m of age) at 7 different locations were enrolled in this study. Heifers from locations 1, 2, 4, and 5 were enrolled in the 14-day+CIDR-PG estrus synchronization protocol, and heifers from locations 3, 6 and 7 were enrolled in the 7-day CO-Synch+CIDR estrus synchronization protocol. Individual BCS were determined 2 d (locations 3, 6, and 7), and 3 d (locations 1, 2, 4, and 5) previously to AI. Within location, heifers were stratified by BCS and randomly assigned to two treatments: 1) fixed-time AI using an AI plastic sheath with three semen outputs (Tri; n = 440), or 2) fixed-time AI using an AI plastic sheath with a single semen output (Single; n = 441). After each insemination the AI plastic sheaths were examined for signs of semen reflux into the sheath. Pregnancy data were analyzed using GLIMMIX procedure of SAS with heifers as the experimental unit, including the fixed effects of treatment, location, BCS, and random effects of sire and AI technician. Heifer BCS differed (P < 0.001) among locations, but was similar (P = 0.606) between treatments (5.5 ± 0.03) and no treatment × location interaction was detected (P = 0.647). Pregnancy rate was similar (P = 0.696) between treatments (52.9 ± 0.02% and 54.4 ± 0.02%, for Single and Tri heifers, respectively). There was a location effect (P < 0.001) on pregnancy rate, ranging from 43.4% to 68.6%, and no treatment × location interaction was detected (P = 0.352). There was a difference (P < 0.001) between AI sheaths on percentage of sheaths with signs of semen reflux after insemination (13.8 vs. 4.8 ± 0.01% for Single and Tri AI sheaths, respectively). However, signs of reflux in the AI sheath was not correlated (P = 0.7225; R = 0.0001) with pregnancy outcome. We conclude that the AI plastic sheath with three semen outputs decreased the percentage of AI sheaths with signs of semen reflux, but failed to increase fixed-time AI pregnancy rates of beef heifers.