Quantity and Quality of Colostrum varies by Quarter
Start out with the assumptions that both the quantity and quality of colostrum yield is the same for each quarter on a cow. To what extent are these two assumptions true?
In an article, "Immunoglobulin variation in quarter-milked colostrum" (Baumrucker, Craig R. and Others, Journal of Dairy Science, June 2014 97:3700-3706) reported initial results looking at these assumptions.
Keep in mind that only 8 mature cows were used. As would be expected the total volume of colostrum varied widely among the 8 cows. Among cows with low colostrum yields the variation by quarter was low. Among cows with high colostrum yields the variation by quarter was quite wide. For practical purposes neither of these findings should suggest that we manage milking fresh cows any differently that we do now.
There were some small differences between front and rear quarters in antibody (IgG) concentration. The sample of cows was so small, however, that these differences could easily been due to chance.
Bottom line is keep milking all four quarters, and, at first milking, keep milking cows out (no partial milking - since if there is a difference between fore and rear quarters the rear quarters, according to these data, have the higher antibody concentration.
The research team is continuing to look into these potential differences - so watch this space in the next year or two for the next chapter.