Absorption of protein and IgG in calves fed a colostrum supplement or replacer

Newborn Holstein bull calves (n = 32) were assigned to receive a colostrum supplement (CS) containing defibrinated bovine plasma or a colostrum replacer (CR) containing an immunoglobulin concentrate obtained by concentrating the immunoglobulin (Ig)G fraction of bovine plasma. The CS and CR contained 11.1 and 21.2% of dry matter as IgG, respectively. Each animal was fed two 454-g feedings at 1 and 8 h of age. The two feedings of CS and CR provided 95 and 187 g of IgG, respectively. Mean plasma IgG at 24 h of age was 8.0 and 13.6 g/L in calves fed CS and CR, respectively, indicating acceptable absorption of Ig from both sources. Mean apparent efficiency of IgG absorption in calves fed CS and CR were 33 and 30%, respectively, and did not differ between treatments. Mean plasma total protein at 24 h in calves fed CS and CR were 4.99 and 4.98 g/dl and did not differ between treatments. Increased plasma protein concentration from 0 to 24 h (4.5 g/L) was lower than the mean increase in plasma IgG concentration during the same period (10.3 g/L), indicating altered protein profile in the blood during the first 24 h of life. Correlation between plasma IgG and total protein at 24 h of age was significant within treatment, but the relationship between IgG and protein in plasma at 24 h varied between treatments. Predicted plasma total protein concentrations at 10 g of IgG/L of plasma at 24 h were 5.4 and 4.2 g/dl, in calves fed CS and CR, respectively. Prediction of plasma IgG concentration using total plasma protein may be inappropriate when calves are fed CS or CR.