PSXIII-19 Effects of Injectable Trace Mineral Supplements at the Initiation of Estrus Synchronization on Pregnancy Rates in Beef Cows

Abstract The objective of this experiment was to evaluate effects of administering injectable trace mineral supplements to beef cows at the initiation of estrus synchronization on pregnancy rates to AI. Four hundred seventeen Angus and Red Angus-based beef cows at two locations were stratified by parity, body condition score, and days postpartum, then randomly assigned to one of 2 treatments; 1) untreated controls (CON; n = 208); or 2) received 90 mg Cu, 60 mg Mn, 30 mg Se, and 360 mg Zn as an injectable TM supplement initiation of synchronization (6 ml Multimin 90 s.q.; ITM; n = 209). All cows received a controlled internal drug release insert (CIDR; 1.38g progesterone) and 100 µg gonadotropin-releasing hormone (GnRH) im, followed in 7 d by CIDR removal and 25 mg prostaglandin F2alpha, followed in 60 to 66 hours with AI and 100 µg GnRH i.m. Cows received an Estrotech heat detection patch on their tailhead at CIDR removal, which was assigned an activation status at AI (yes = ≥50% of patch activated; no = < 50%). Pregnancy status was determined via transrectal ultrasound on day 35 to 40 after AI to determine pregnancy rates to AI in response to treatments. No location × treatment interaction was present (P = 0.66), but pregnancy rate was greater (P < 0.01) for Location 1 (76.9%; 70 of 91) than for Location 2 (58.0%; 189 of 326). However, no differences (P = 0.50) in pregnancy rates were observed among CON (123/208; 63.5%) and ITM (127/209; 60.8%). Overall, 56.6% of cows had activated estrus detection patches at AI, and more cows with activated patches became pregnant (169/236; 71.6%) compared with cows having unactivated patches (90/181; 49.7%). In this experiment, ITM administration at the initiation of estrus synchronization had no negative effects on pregnancy rate to AI.