When a mother gives birth to her infant, her mammary glands produce a pre-milk formula called colostrum.
Colostrum is super-saturated with hormones.
Puppies should not drink human breast milk and calves should not drink pig's milk. Neither should dolphins drink cat's milk, nor squirrels drink camel milk. That is not nature's plan. Instinctively, we know that dog's milk and pig's milk contain substances best suited for those specific species. Most human adults would be disgusted at the thought of consuming canine or porcine hormones, lactoferrins or immunoglobulins.