111 Factors affecting transfer of passive immunity in beef calves

Abstract Data from 9 calving experiments were used to investigate relationships of dam, calf, and colostrum factors with passive transfer in beef calves. Serum was collected at 48.33 ± 1.25 (SD) h of age for 313 calves, and single rear quarter colostrum yields were determined pre-suckling for dams of 117 calves. Serum and colostrum IgG concentrations were determined by ELISA. Relationship of serum IgG with colostrum variables was determined using Pearson correlation coefficients. Serum IgG was positively correlated (P ≤ 0.002) with colostrum IgG (r = 0.47) and protein (r = 0.45) concentrations and colostrum total IgG (r = 0.28) but tended to be negatively correlated (r = -0.17, P = 0.06) with colostrum yield. Based on passive transfer thresholds in the literature, 3 calves (0.96%) had 8 mg/mL serum IgG, 16 calves (5.1%) 16 mg/mL, and 43 calves (13.7%) had 24 mg/mL. For this analysis, calves with serum IgG 24 mg/mL at 48 h were considered to have failure of passive transfer (FPT). Continuous variables (dam BW and calf size, 48-h serum chemistry panel, and time to stand) were compared for FPT versus non-FPT calves using a mixed model with FPT class (fixed effect) and experiment (random effect). Calves with FPT had less (P ≤ 0.03) circulating triglycerides, glucose, calcium, magnesium, total protein, globulin, and gamma-glutamyl transferase but greater (P ≤ 0.001) circulating non-esterified fatty acids, sodium, chloride, and total bilirubin than non-FPT. Effects of categorical variables on calf 48-h serum IgG were determined using separate mixed models with variable (fixed) and experiment (random). Primiparous dams gave birth to calves that had less (P = 0.05) serum IgG at 48 h than multiparous dams. Calves born to moderate dams (BCS = 5) had less (P = 0.007) serum IgG than those born to fleshy dams (BCS ≥ 6) and tended to have less (P = 0.08) serum IgG than calves born to thin dams (BCS 5). Calf sex, calving season, calving difficulty score, and vigor score at 10 min did not affect (P ≥ 0.19) serum IgG. Relationships of calf 48-h serum IgG with continuous variables was also determined using Pearson correlation coefficients, and only r ≥ 0.20 or ≤ -0.20 are reported. Serum IgG was positively correlated (P ≤ 0.005) with 48-h serum total protein (r = 0.75), globulin (r = 0.76), gamma-glutamyl transferase (r = 0.32), and potassium (r = 0.20). Serum IgG was negatively correlated (P 0.001) with gestation length (r = -0.22) and 48-h serum albumin (r = -0.43), sodium (r = -0.24), and total bilirubin (r = -0.27). Overall, beef calves in this dataset generally had successful passive transfer that was associated with several dam, calf, and colostrum factors.