I have an Animal Science degree and worked for a company that provides
vaccines to the dairy industry for many years, so I have some familiarity
with bovine milk production. It has been a while since I got my degree or
worked, so some of this information may be a bit outdated!

I suspect the biggest differences in cost are due to 1) economies of scale,
2) that any time something medical is done for a human the cost seems to be
multiplied by a significant factor, whether its warranted or not, and 3)
dairies are not very clean places and the milk is going to be pasteurized
so testing for everything is unrealistic and unnecessary.

Dairy cows are tested for TB and Brucellosis, I believe on a yearly basis.

Some dairies are able to monitor the SCC (somatic cell count) on each cow
on a daily basis, others just check the bulk tank and if it is high they
will check SCCs on each cow or do a CMT (California Mastitis Test) on each
cow to find which animal(s) are affected by mastitis. Once mastitis is
diagnosed (using CMT, or often you can tell just by looking at the small
amount of milk that is removed prior to milking to help stimulate letdown),
antibiotics are used and the milk from that animal is not pumped into the
bulk tank, so it doesn't end up in the milk supply. The bulk tank milk is
also tested for antibiotics to double check that none gets through. If the
bulk tank test shows that antibiotics are present then the dairy has to
purchase all of the milk in the truck that their milk contaminated. I
believe that the creamery will also refuse the milk if the SCC count is too
high.

Most, if not all, dairies don't regularly culture milk samples to find out
what bacteria are present - if a dairy is having a problem with recurrent
mastitis that is one of the tools they can use to help solve it, but it's
not something that's done routinely as it would be cost prohibitive.

Hope this helps!

Hilary Pollock

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