Concentration and heritability of immunoglobulin G and natural antibody immunoglobulin M in dairy and beef colostrum along with serum total protein in their calves

Lay Summary Understanding how breed influences immunoglobulin (Ig) G and natural antibody (NAb) IgM concentrations in colostrum can improve bovine colostrum quality and calf health. Maternal colostral IgG is abundant, persistent, and pathogen specific. Natural antibody-IgM is less abundant but mediates broad, short-lived, nonspecific pathogen protection, and potentially important against septicemia. Colostral IgG and NAb-IgM concentrations were compared between dairy and beef cows and among cross-bred beef cows. Heritabilities were calculated to assess the practicality of selective breeding. Serum total protein (STP) in neonatal dairy and beef calves was estimated using refractometry. Colostrum from beef cows had higher concentrations of IgG than dairy cows. Beef cows with higher Angus ancestry produced colostrum with lower IgG concentrations than other mixed breeds. Heritability of colostral IgG was low (0.04-0.14). Failure of passive transfer was similar in dairy and beef calves, but a significantly larger proportion of beef calves had excellent STP (>= 6.2 g/dL). There were no differences in NAb-IgM titers between dairy and beef cows or among beef breeds. Colostral NAb-IgM varied widely among individuals (42-fold) and was moderately heritable (0.11-0.24). These results suggest that selective breeding to improve colostrum quality is feasible and practical to improve calf health. Natural antibody (NAb) immunoglobulin M is germline-encoded and provides a broad level of protection against bacterial pathogens. In the current study, colostral NAb was highly variable among individual dairy and beef cows and moderately heritable, providing an opportunity through selective breeding to improve colostrum quality and reduce septicemia in neonatal calves. Immunoglobulin (Ig) G and natural antibody (NAb) IgM are passively transferred to the neonatal calf through bovine colostrum. Maternal IgG provides pathogen- or vaccine-specific protection and comprises about 85% of colostral Ig. NAb-IgM is less abundant but provides broad and nonspecific reactivity, potentially contributing to protection against the dissemination of pathogens in the blood (septicemia) in a calf's first days of life. In the dairy and beef industries, failure of passive transfer (FPT) of colostral Ig (serum total protein [STP] <5.2 g/dL) is still a common concern. The objectives of this study were to: (1) compare colostral IgG concentrations and NAb-IgM titers between dairy and beef cows; (2) assess the effect of beef breed on colostral IgG; (3) compare passive transfer of colostral Ig in dairy and beef calves; and (4) estimate the heritability of colostral IgG and NAb-IgM. Colostrum was collected from Holstein dairy (n = 282) and crossbred beef (n = 168) cows at the University of Guelph dairy and beef research centers. Colostral IgG was quantified by radial immunodiffusion and NAb-IgM was quantified by an enzyme-linked immunosorbent assay. In dairy (n = 308) and beef (n = 169) calves, STP was estimated by digital refractometry. Beef cows had significantly greater colostral IgG (146.5 +/- 9.5 standard error of the mean [SEM] g/L) than dairy cows (92.4 +/- 5.2 g/L, P <0.01). Beef cows with a higher proportion of Angus ancestry had significantly lower colostral IgG (125.5 +/- 5.8 g/L) than cows grouped as "Other" (142.5 +/- 4.9 g/L, P = 0.02). Using the FPT cutoff, 13% of dairy and 16% of beef calves had FPT; still, beef calves had a significantly larger proportion with excellent passive transfer (STP >= 6.2 g/dL, P <0.01). The heritability of colostral IgG was 0.04 (+/- 0.14) in dairy and 0.14 (+/- 0.32) in beef. Colostral NAb-IgM titers in dairy (12.12 +/- 0.22, log(2) [reciprocal of titer]) and beef cows (12.03 +/- 0.19) did not differ significantly (P = 0.71). The range of NAb-IgM titers was 9.18-14.60, equivalent to a 42-fold range in antibody concentration. The heritability of colostral NAb was 0.24 (+/- 0.16) in dairy and 0.11 (+/- 0.19) in beef cows. This study is the first to compare colostral NAb-IgM between dairy and beef cows. Based on the range in NAb-IgM titers and the heritability, selective breeding may improve colostrum quality and protection for neonatal calves in the early days of life.