Monday, September 25, 2017

How Many Antibodies We Feed End up in the Blood?

A standard method is used to estimate the proportion of antibodies fed to a calf that end up in her blood. It requires knowing:
  • calf body weight
  • volume of colostrum fed
  • IgG concentration in colostrum
  • IgG concentration in blood serum
100 calves were in the study. "After a normal calving, the heifer received either 4 or 5.6L of colostrum within 4 hours of birth, [a sample was taken of the "as-fed" colostrum] and a blood sample was collected between 24 and 36 hours after birth." p3282

The measure is called "apparent efficiency of absorption" or abbreviated as AEA.

The AEA values:
  • Average = 28.1%
  • Median = 27.5%
  • Minimum = 7.7%
  • Maximum = 59.9%
Most of the calves (70%) had values between 21% and 40%.

BOTTOM LINE? Using "average" conditions, in order to end up with at least 5g/dLantibodies  in the calf's blood we need to feed roughly 180g total in the first feeding (28% AEA). [This uses 5g/dL as an acceptable threshold for successful passive transfer of immunity. Excellent quality colostrum (80g/L) will deliver this in 2.7 quarts. Poor quality colostrum (30g/L) would require 7 quarts to equal 200g of antibodies.]

As a side note, one of the dairies fed 4 quarts as first feeding within 4 hours of birth and then an additional 2 quarts before 12 hours of birth.

The two- feeding protocol (total of 6 quarts) resulted in both an increase in AEA and a 68% increase in circulating antibodies in the blood compared to the single 4-quart feeding. These data agree with one of my client dairies that has a two-feeding colostrum protocol - they have well over 90% of the calves testing at 5.5g/dl blood serum total proteins.

Reference: Halleran, J. and Others, "Short Communication: Apparent efficiency of colostral immunoglobulin G absorption in Holstein heifers." Journal of Dairy Science 100:3282-3286 September 2017

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