Mammary immunoglobulin transfer rates following prepartum milking

摘要

Colostrum formation is thought to occur slowly over an extended period (4 wk) prepartum. Furthermore, colostrum formation is highly variable among cows in total volume, IgG_1 concentration, and mass obtained at first postpartum milking. Recent work has suggested that a rapid transfer of IgG_1 to secretions may occur if animals are milked prepartum. Our objective was to establish the concentration, mass, and mass transfer rates of IgG_1 in multiparous Holstein cows (n = 11, parity = 3.6 ± 1.1) milked prepartum (-74 to -1 h) and again around 4 h postpartum. Blood concentrations of IgG_1 were very low (<1 mg/mL) in 7 cows at prepartum milking and did not decline following prepartum milking. Cows showed variability in the capacity to recover total volume, IgG_1 concentration, and IgG_1 mass. Three groupings of cows were considered based on the time between the 2 milkings (prepartum + 4 h postpartum): long-time (-74 to -54 h, n = 3), medium-time (-25 to -17 h, n = 4), and short-time (< -13 h, n = 4) groups. The average rates of transfer of these groups were 1.4 ± 0.8, 3.0 ± 1.3, and 25.1 ± 15.8 g/h, respectively. The data indicate that a longer time between prepartum and postpartum milking is not a main factor in IgG_1 secretion transfer. Furthermore, because blood concentrations did not change after prepartum milking and the mass of blood plasma IgG_1 was not sufficient to account for the mass occurring in postpartum colostrum, a source of IgG_1 other than blood circulation appears to be present during colostrogenesis.