There is a HUGE difference between feeding yourself and others with the milk of a cow and a mother feeding a baby her own milk. The difference is choice and exploitation.
The cow has no choice in the matter and is properly considerred exploited in the arrangement.
A human mother has all the information she needs to make the decision to feed her baby her own breast milk.
@SuperMouse‘s example of a vegan mom who won’t feed her child from her own breasts doesn’t show clearly why she didn’t want to, but the point is she has the choice in the matter. (p.s. if you ask me mom’s an idiot in this case)
As far as sperm goes, again choice is the key. Presumably the man in that scenario has given consent.
If we could talk to the animals and knew that they were willingly giving their milk and meat to us that’s one thing (e.g. the cow in Douglas Adam’s ‘Hitchhiker’s Guide to the Galaxy, at the end of the universe…) but until we have that communication established there is a lot of evidence that factory-farmed meat and dairy is NOT something the animals would chose to give us.