Relationship between milking fraction and immunoglobulin g concentration in first milking colostrum from holstein cows

Abstract

The objective of this study was to describe immunoglobulin G (IgG) concentrations in various milking fractions (0% fraction [cisternal], 25% fraction, 50% fraction, 75% fraction, 100% fraction [alveolar], or composite sample) in first milking colostrum from Holstein dairy cows. First milking colostrum was collected from 26 primiparous and multiparous Holstein cows on a commercial dairy farm in western Wisconsin. For each cow, 10-mL colostrum samples were collected representing the following milking fractions: cisternal colostrum (first 10-15 seconds), 25%, 50%, 75%, 100% (alveolar), and a composite sample (entire milking), and tested for IgG concentration (mg/mL). Contrast analysis showed that IgG concentrations were significantly higher in cisternal colostrum samples as compared to IgG concentrations in the 25% fraction, the 50% fraction, the 75% fraction, and the composite sample. Levels of IgG in cisternal samples were not different than levels in the 100% (alveolar) fractions. Apart from the cisternal samples, IgG concentrations were not different among the other milking fractions tested. Producers or researchers wishing to measure colostrum quality should avoid using forestripping samples for testing purposes, as these samples may overpredict the IgG concentration in what will be fed to the calf. The current study found no difference in IgG concentration among the other milking fractions. However, when considering the effect of milking fraction on other milk components that may be of importance to the neonatal calf, including fat, producers should completely milk out the cow at the time of first colostrum harvest.