Colostral immunoglobulin concentrations in Holstein and Guernsey cows

Objective-To compare the concentration of IgG in colostrum between Holstein and Guernsey cows and among cows of various lactations. Design-Crass-sectional cohort study. Sample Population-Colostrum samples from 77 Holstein and 24 Guernsey cows. Procedure-Colostrum samples were obtained from 101 cows. Colostral IgG conc entration was determined. using a radial immunodiffusion assay. Regression analysis was used to determine the effect of breed and lactation number on colostral IgG concentration. Survival analysis and t-tests were used to com pare the proportion of colostrum samples that would provide 100 g of IgG fo r various volumes of colostral intake. Results-Guernsey cows produced 36.4 g of lgG/L of colostrum more than that of Holstein cows-Cows in the third or greater lactation produced 19.5 g of IgG/L of colostrum more than that of first-lactation cows. The IgG concentr ation df colostrum produced by second-lactation cows did not differ signifi cantly from that produced by first-lactation cows. The colostral IgG concen tration of these Holstein and ;Guernsey cows was higher than values that ha ve been reported elsewhere. Conclusions and Clinical Relevance-Volume of colostrum needed to meet IgG i ntake goals is probably lower for Guernsey cows than Holstein cows. Colostr um from first-lactation cows was adequate in IgG content. The practice:of d iscarding colostrum from first-lactation cows on the basis of inadequate Ig G content was not justified in this study.