Adding Bacteria to Milk with an
The recipe seems to be fairly simple.
Start with clean milk replacer powder, put warm water into mixing jar, add powder to jar, mix. Sample the milk from the jar. Presto! Contaminated milk replacer ready to feed calves!
In the study reported by Medrano-Galarza and Others in the March issue of the Journal of Dairy Science from 17 dairies in southern Ontario (Canada) using automatic feeders roughly 3 out of 4 dairies managed to add more than 100,000cfu/ml bacteria to the milk replacer before it left the mixing jar.
Then, the same milk replacer was sampled coming out of the hose connecting the mixing jar to the nipple. Now 4 out of 5 farms elevated the bacterial contamination to over 100,000 cfu/ml.
I cannot believe these dairies were trying to make their calves sick. The study included calf diarrhea rates for these calves in all four seasons of the year. The rates were:
Fall = 23%
Winter = 27%
Spring = 25%
Summer = 16%
In my opinion this shows that calves are very tough critters - in spite of this continuous exposure to bacteria in all their milk replacer ration most of them still neither died or were observed with diarrhea. [Mortality was reported at 4% - lower than most values for both USA and Canada.]
Also reported were contamination levels with coliform bacteria in samples coming directly from the mixing jar. These rates of over 10,000cfu.ml coliforms were:
Fall = 12%
Winter = 17%
Spring = 12%
Summer = 17%
Calves are tough critters.
How much better could their feed conversion have been without the constant drag of bacterial exposure in their milk?
Reference: Medrano-Galarza, Calalina, S.J. LeBlanc, A. Jones-Bitton, T.J. DeVroies, J. Rushen, A.M. de Passille, M.I. Endres, D.B. Haley. "Associations between management practices and within[pen prevalence of calf diarrhea and respiratory disease on dairy farms using automated milk feeders." Journal of Dairy Science 101:2293-2308 March 2018.