Immunoglobulin G absorption dynamics in neonatal calves: An investigation of the effects of casein presence in colostrum

Casein presence in colostrum may affect the absorption of immunoglobulins in neonate dairy calves. This randomized controlled trial investigated the effect of casein presence in colostrum replacer on serum IgG dynamics on calves. Seventy-one calves (BW: 45.3 ± 5.9 kg) were randomly assigned to 1 of 3 colostrum treatments: colostrum replacer with casein addition to match the maternal colostrum (CR+C; n = 23; 85 g/L of IgG; Premolac Plus, Zinpro; 95 g/L of casein); colostrum replacer without casein addition (CR-C; n = 23; 85 g/L of IgG; Premolac Plus, Zinpro); and maternal colostrum (MC; n = 25; 85 g/L of IgG). Dystocia scores were recorded, and 3 h after birth, calves received 3.7 L of solution via tube feeding. Blood samples and calf vigor assessments were conducted at colostrum feeding (0 h) and 6, 12, 18, 24, 36, 48, and 72 h after colostrum feeding. Serum was analyzed for IgG concentration (g/L) and serum total protein (g/dL; STP). In addition, apparent efficiency of absorption of IgG (%; AEA), maximum IgG concentration (g/L; Cmax), time to maximum IgG concentration (h; Tmax), IgG area under the curve (g/L × h; AUC), and the apparent IgG persistency (%; AIP) were calculated. An ordinal logistic model was used to evaluate the odds of treatment improving a calf's vigor category from colostrum feeding (3 h of age) to 72 h after colostrum feeding. Vigor score was categorized as abnormal (≤4), average (5), or alert (≥6), with hour as a fixed effect. Mixed linear models were used to evaluate the effect of colostrum treatments on serum IgG, STP, AEA, Cmax, Tmax, AIP, and AUC, with time, dystocia score, calf sex, BW, and a treatment by time interaction as fixed effects. Calf vigor scores were not influenced by colostrum treatments. Treatment and time interaction affected serum IgG and STP levels after colostrum feeding. Serum IgG was lower for CR with casein addition (CR+C- compared with CR-C-treated calves) from 6 to 72 h. No difference was observed for serum IgG between CR+C- and MC-treated calves, regardless of time. Additionally, treatment affected AEA, with CR+C-treated calves exhibiting reduced AEA compared with CR-C calves (CR-C = 36.7 ± 2.0%, CR+C = 27.4 ± 2.1%, MC = 31.3 ± 2.1%). Treatment affected the Cmax, with CR+C-treated calves exhibiting reduced Cmax compared with CR-C and MC calves (CR-C = 29.5 ± 1.3 g/L, CR+C = 21.1 ± 1.3 g/L, MC = 26.2 ± 1.4 g/L). No differences were observed between treatments for Tmax and AIP. The AUC was lower for CR+C- compared with CR-C- and MC-treated calves (CR-C = 2,641.2 ± 117.5 g/L × h, CR+C = 1,719.3 ± 120.6 g/L × h, MC = 2,197.5 ± 124.4 g/L × h). For STP, no differences were observed between CR+C- and CR-C-treated calves (from 6 to 72 h). However, calves fed CR+C and CR-C displayed lower STP levels compared with MC-treated calves (from 12 to 24 h). These findings suggest that casein presence in colostrum replacer influences calf serum IgG concentration, STP levels, and AEA in neonatal calves.