Alternative Trace Mineral Supplementation Strategies for Beef Cattle

Abstract This study evaluated an injectable trace mineral (ITM) source containing Cu, Mn, Se, and Zn (Multimin90) administered to gestating beef cows receiving a free-choice 2:1 mineral supplementation. Two hundred and eight multiparous and primiparous cross-bred cows (BW = 621 kg ± 96.6 kg; avg. 4 yr. old) were randomly allotted into one of two treatments and received either i) ITM + inorganic, granular 2:1 trace mineral free-choice; or ii) inorganic, granular 2:1 trace mineral free-choice alone (CON). A cross-over design was used for the study and cows in year 2 (n = 202) were allocated to the other treatment group. The ITM was administered at 4 weeks pre-calving and 4 weeks pre-breeding. Body weight and body condition score (BCS) were evaluated at injection times and pregnancy diagnosis using a weigh scale and a 5-point BCS scale (Lowman et al., 1976). Mineral status was determined from blood serum mineral concentration at 4 weeks pre-calving, 4 weeks pre-breeding, and at pregnancy diagnosis. Cows grazed grass-legume pastures in the summer and had access to dugout and well water sources. Cows were managed as two groups during spring and while on summer pasture during a 63-day breeding season until weaning. Serum blood mineral concentrations at 4 weeks pre-calving, 4 weeks pre-breeding, and pregnancy diagnosis did not differ (P > 0.05) between treatment groups. Copper conetrations at pregnancy diagnosis tended (P = 0.09) to be greater for the ITM cows compared with CON cows. At 4 weeks pre-calving and pregnancy diagnosis, Cu and Mn concentrations were numerically greater in the ITM group compared with the CON group. There were no significant results (P > 0.05) for cow BW, BCS, and days pregnant. Over 2-yr, pregnancy rates were 93.6% and 88.6% for the ITM and CON cows, respectively. Calves born to ITM and CON cows did not differ (P > 0.05) for birth weight, Julian birth date, age at weaning, average daily gain, or adjusted 205 d wean weight. However, CON calves tended (P = 0.07) to be heavier at weaning. Study findings suggest that administering an ITM source to beef cows does not improve cow and calf performance, which suggests that more research in this area is required. Additionally, pregnancy rates in beef cattle may be improved with the use of an injectable trace mineral.