Cow Nurses Lambs
The vintage photo shown below is a personal snapshot I picked up on Ebay. It got me thinking about how common cross-suckling of young may be between different species.
A picture, probably dating from the 1930s, showing a man in overalls holding a cow nursing three lambs.
Nursing Across Species
There have been many cases of animals nursing members of another species. In this case it seems that the three lambs were orphaned or the ewe could not provide milk for them. So they have been fostered onto a cow.
In this case I am not sure how willing the cow is, but she is putting up with the situation. I have not been able to find any other case of lambs being fostered onto a cow.
It seems that the mothering instinct in mammals is sometimes strong enough to encompass young that are not their own, or even of another species. Examples can even be found on ancient mosaics such as this one showing lion cubs nursing from a donkey.