Influence of repeated trace mineral injections during gestation on beef heifer and subsequent calf performance

Commercial Angus heifers (n = 190; body weight (BW) = 315 +/- 49.3 kg) were used to determine the effects of trace mineral injections during gestation on heifer and subsequent calf performance. Heifers received three previous subcutaneous trace mineral (Multimin 90 [MM]; n = 93) or sterilized physiological saline (CON; n = 97) injections approximately 90 d apart. These treatments were maintained and subsequent injections were given 205, 114, and 44 +/- 26 d prepartum. Heifers were provided free-choice inorganic minerals. Heifer BW and body condition scores (BCS) were collected at trial initiation (296 +/- 26 d prepartum) and 5- to 10-week intervals thereafter. Liver samples were collected at trial initiation, 5 and 176 +/- 3 d postpartum from a subset of cows to determine trace mineral status. Milk production was assessed on 80 cow-calf pairs (40/treatment) at 71 +/- 15 d postpartum. Cows were artificially inseminated (AI) 82 d postpartum and then exposed to bulls for 38 d. Data were reported from 174 calves (n = 87 calves/treatment). Calf liver samples were collected 5 and 147 +/- 3 d postpartum to determine trace mineral status. Calf weaning BW was collected at 159 +/- 26 d postpartum. Calf performance including calving date, birth BW, weaning BW, average daily gain (ADG), and health data were collected. Heifer BW and BCS did not differ (P >= 0.72) throughout the experiment. Multimin heifers tended (P = 0.08) to have greater initial liver Se and tended to have decreased (P = 0.08) initial liver Zn compared with CON. At calving, MM cows had increased (P <= 0.01) liver Cu and Se. There was no difference (P >= 0.47) in Julian calving date, calving percent, or unassisted births. Calf birth BW was lesser (P = 0.02) for MM than CON calves, and MM calves had greater (P = 0.03) liver Cu concentrations at birth than CON calves. Despite MM cows having increased (P < 0.01) milk production, calf weaning BW and ADG were not different (P >= 0.87). In addition, calf morbidity and mortality were not different (P >= 0.43) between treatments. Calf mineral status was not different (P >= 0.57) at the time of weaning regardless of treatment; however, MM cows had decreased (P = 0.03) liver Zn. Multimin cows had decreased (P = 0.05) AI pregnancy rates, yet there was no difference (P = 0.34) in overall pregnancy rate. Supplementing an injectable trace mineral during heifer development and gestation increased cow milk production and resulted in decreased AI pregnancy rates; however, there was no effect on overall pregnancy rates or preweaning calf health or performance.