The Effects of Slow-Release Copper Boluses on Cow Reproductive Performance and Calf Growth

Abstract

The effect of copper, orally administered via slow-releasing boluses, was examined in two Kansas beef herds. In herd 1, 34 cows and calves were divided into a treated (B; n = 18) and a control group (C; n = 16). The cattle in herd 1 were prediagnosed as copper-deficient by liver biopsy analysis. Cows assigned to B received two boluses, and their respective calves received one. Serum samples were collected at d 0 and 64. Liver samples, collected at d 64 and 106, were analyzed for copper and iron. Liver iron levels tended (P=.068) to be lower in group B. Through d 106, cow ADG did not differ between treatments (.29 vs .28 kg/d for B and C, respectively). Calf ADG was determined 42-d posttreatment. Control calves tended (P=.063) to have a higher ADG. In herd 2, dams were divided into a treated (B; n = 276) and control group (C; n = 830). The cattle in herd 2 were not prediagnosed as copper-deficient, however, unexplained reductions in fertility, coupled with the high prevalence of copper deficiency in this region, made this herd a likely candidate for this study. As in herd 1, dams assigned to B received two boluses, and their respective calves received one. Approximately, 1 mo after treatment, reproductive parameters, including AI pregnancy rate, AI first service conception rate, and number of inseminations per female, were evaluated in all dams. Liver (n = 10) and serum (n = 30) samples were collected randomly from dams on d 0, 97, and 154. Additionally, bull and heifer calf weaning weight was examined in herd 2. No treatment differences were detected in serum copper concentration. On d 97 and d 154 of treatment, bolus administration elevated (P<.05) liver copper. No treatment differences were detected in dam reproductive performance. Bull calves in herd 2 were divided into a treated (BB; n = 56) and a control group (BC; n = 43). Weaning weights were heavier (P<.05) (269 d posttreatment) for BC (354 kg) than for BB (340 kg). Heifer calves in herd 2 also were divided into a treated (HB; n = 36) and a control group (HC; n = 37). Weaning weights tended (P=.093) to be heavier (288 posttreatment) for HC (327 kg) than for HB (313 kg). Orally administered copper boluses tended to increase liver copper, decrease liver iron, and adversely affect calf weight gain; a response in reproductive parameters was not noted.