Impact of Three Colostrum Replacement Strategies on Immunoglobulin G Absorption and Growth in Beef Calves

Abstract: Background Evidence-based colostrum replacement recommendations are lacking for beef calves. Objectives To determine the apparent efficiency of absorption (AEA) of Immunoglobulin G (IgG) in beef calves receiving complete colostrum replacement and compare the effects of three replacement strategies on AEA, transfer of passive immunity (TPI), and growth. Animals 45 newborn Angus calves from university herd Methods Randomized clinical trial. Calves were separated from their dams at birth and received either 3.2L (167g IgG) of colostrum within 3 hours (Group A), 4.2L (245g IgG) over two feedings within 8 hours (Group B), or 4.8L (245g IgG) over three feedings within 14 hours (Group C). Serum IgG concentration was measured at 0, 6, 12, and 24 hours. The AEA, TPI, and average daily gain (ADG) at weaning were compared among groups using ANOVA, Kruskal-Wallis, Fisher’s Exact, or χ² tests, as appropriate. Results The median AEA was higher in group A (28.5%), compared to groups B (20.7%, p=0.047), and C (18.8%; p=0.005). Median serum IgG concentrations at 24 hours were similar at 20.2 g/L (range 6.4-29.4 g/L), 21.2 g/L (range 15.4-32.6 g/L), and 20.1 g/L (range 14.0-27.6 g/L) in groups A, B and C, respectively (p=0.65). The proportion of calves with IgG concentrations < 10 g/L was small and comparable among study groups (7%, 0%, 0%, p=0.99). There were no significant differences in ADG (p=0.17). Conclusions and Clinical Importance Early intervention with any of the strategies evaluated was effective in preventing IgG concentrations < 10g/L, but did not ensure IgG concentrations >24 g/L.