I've had cases where a new calf starts nursing off of two cows, the actual dam and what I call a "wet nurse." The trouble is that this "wet nurse" is going to be having her own calf in a few days. I'm concerned about the effect this could have on colostrum in the cow that hasn't calved yet. Did the "little robber" get all the good stuff?
I checked with one of my experts and he does not know of any conclusive research on this issue. What we do know is that colostrum is only produced once per pregnancy--starting a few weeks in advance of calving and accelerating as calving approaches. Each case would be different as to how much colostrum a cow produces and how much is lost to the "robber" calf.
The best assumption would be that the actual calf of that cow would be at high risk for Failure of Passive Transfer (FPT). This lack of passive immunity increases the risk of neonatal calf diseases especially of the gastrointestinal and respiratory tracts, and has been shown to have negative effects all the way to the feedlot.
One good option would be to give that calf a colostrum replacer containing at least 100 grams of immunoglobulin G (IgG) within the first few hours of life. This is something we recommend for any calf at risk of FPT. Some suggest 150 to 200 grams may be a better number. Keep a few bags around during calving season. It's a good insurance policy.
There are colostrum supplements on the market that typically contain a half or less of the IgG of replacers. They often cost less. Replacers contain enough IgG to get a calf's serum IgG levels to at least 10 mg/ml even in the event the calf receives no colostrum.
That said, since there are no "do overs" after the first 24 hours, I would spend the extra money for a very high-quality colostrum replacer.`
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