They do. A lady in India nursed an orphaned newborn calf alongside her child.



Another nursed a monkey



The "Bishnoi" tribe are nature lovers and protectors of wild buck deer from poachers. They nurse the orphaned fawn at the breast





Cross nursing among species is nothing new. Don't want to make it an abnormal thread with too many such video clips, but there is definitely more such cases out there - google them.

For instance:

Amazonian rainforest tribal women nurse orphaned monkeys.


In Thailand, there was a call sent out to lactating mothers to help with white tiger cubs born in captivity.

Nursing piglets in Philippines, many women having breastfed puppies whose mother have died in birthing process etc.

It is not so uncommon after all.