Genetic aspects of colostrum quality traits including immunoglobulin G in Holstein cows

Immunoglobulins G (IgG), A (IgA), and M (IgM) account for 80% of total proteins in bovine colostrum and are important for the passive transfer of antibodies from the dam to the calf. The practical difficulties of samples collection and the high cost of gold standard analysis have so far hampered the estimation of genetic parameters of both bovine colostrum and mature milk IgG, IgA, and IgM concentrations (g/L). In the present study, 672 colostrum samples from the same number of Holstein cows were collected within 6 h after calving. The concentration of IgG, IgA, and IgM was determined through radial immunodiffusion. The pedigree included 6,714 animals, i.e., cows with phenotypes and up to 6 generations of ancestors. Linear models were used to estimate variance and covariance components through univariate and bivariate analyses, respectively. The model included the random animal additive genetic effect and the fixed effects of parity (5 levels: 1, 2, 3, 4, and ≥5), season of calving (4 levels), year of calving (2 levels), and herd (9 levels). Colostrum IgG, IgA, and IgM averaged 93.24, 4.89, and 5.16 g/L, respectively, and were normally distributed. Heritabilities (±standard error) of IgG, IgA, and IgM were 0.14 ± 0.14, 0.33 ± 0.16, and 0.19 ± 0.14, with coefficients of genetic variation of 13.1, 30.8, and 19.7%, respectively. The IgG correlated phenotypically with IgA (0.52 ± 0.04) and IgM (0.59 ± 0.03), and IgA correlated with IgM (0.48 ± 0.04). Overall, genetic correlations were weak (<0.10) except for the association between IgG and IgA (0.37 ± 0.41). Results agreed with the literature and highlighted that the most important colostrum quality trait, i.e., the IgG, tended to be the least heritable Ig. Further efforts will allow to improve data size and variability and will be focused on coupling Ig data with other information to estimate the association between Ig of the colostrum administered to the calf and health and productivity in the subsequent lactations.