Effect of a trace mineral injection on pregnancy rate of Angus beef heifers when synchronized using the 14-day controlled internal drug-releasing insert-prostaglandin F2α protocol at a commercial feedlot

Purebred black Angus (n = 207, BW = 347 ± 3.0 kg) and commercial black Angus heifers (CBA, n = 529, BW = 335 ± 2.3 kg) were used to examine the effect of an injectable trace mineral (TMI) providing copper, manganese, selenium, and zinc on reproductive performance. Heifers were fed a ration supplemented with copper, manganese, selenium, and zinc (formulated to provide 10, 15, 0.17, and 55 mg/kg of DM, respectively). At processing, 30 d before the start of breeding, heifers received 4 mL of TMI or no injection (CON). Heifers were synchronized using a 14-d controlled internal drug-releasing (CIDR) plus prostaglandin F2α protocol. For purebred black Angus, there was no difference (P = 0.67) in AI conception between CON (52%) and TMI (52%). Conception of CBA to first-service AI also did not differ (P = 0.52) between the CON (55%) and TMI (50%). Gonadotropin-releasing hormone and a CIDR were given to CBA 11 d after AI. The CIDR was removed 7 d later, and second-service AI was performed based on heat-patch activation over a 5-d period. There was no difference in the proportion of CBA that received second-service AI (21 vs. 22% for CON and TMI, respectively). Following second-service AI, CBA were exposed to bulls for 27 d. Overall pregnancy rate of CBA did not differ (P = 0.53) between CON (87%) and TMI (85%). These data suggest that TMI has no effect on reproductive performance of heifers being fed adequate concentrations of trace mineral in the diet.