Short Communication: Effect of pH on Absorption of Immunoglobulin G in Neonatal Calves

We fed newborn calves (n = 60) maternal colostrum (n = 12) or a colostral supplement product derived from edible bovine serum (n = 48). Sodium citrate was added to supplements to achieve a final pH of 7.5, 7.0, 6.0, and 5.0. Calves were fed colostrum (2 L/feeding) or supplement (454 g reconstituted in 2 L of water) at 1.2 and 12.6 h of age, which provided a total of 156 (colostrum) or 90 (supplement) g of IgG. We sampled jugular blood at 0 and 24 h of age to determine plasma IgG. Mean plasma IgG concentrations at 0 and 24 h of age were 0 and 6.7 g/L and were markedly higher in calves fed maternal colostrum compared with sup-plements (10.7 vs. 6.5 g/L) and were higher in Jersey vs. Holstein calves (8.5 vs. 6.1 g/L). Estimated appar-ent efficiency of IgG absorption was unaffected by treatment and averaged 20%. These data indicate that pH of colostral supplements between 7.5 and 5.0 do not markedly influence the efficiency of IgG absorption. (Key words: calves, colostrum, IgG) Abbreviation key: AEA = apparent efficiency of IgG absorption; CS = colostrum supplement; MC = mater-nal colostrums. The provision of passive immunity to neonatal calves has traditionally been accomplished by feeding sufficient amounts of maternal colostrum (MC) within the first 24 h of life. In recent years, sources of exoge-nous IgG have been developed, usually referred to as colostrum supplements (CS). The chemical composi-tion of such products may affect the efficiency with which IgG are absorbed. Differences in absorption o