Final answer:
Cow's milk is not suitable for puppies due to the risk of lactose intolerance and because its proteins are difficult for puppies' immature digestive systems to digest. Colostrum, on the other hand, is essential for newborns' immune support and provides necessary nutrients.
Step-by-step explanation:
Cow's milk should not be offered to puppies primarily because it may cause lactose intolerance. Puppies can have difficulty digesting lactose, which is a disaccharide present in cow's milk. When puppies ingest lactose, it can lead to symptoms such as bloating, cramps, nausea, and vomiting due to the lactose being not well digested in the small intestine and causing gas when it reaches the large intestine.
In addition, cow's milk has more protein and minerals compared to breast milk and the proteins found in cow's milk are hard for an infant animal’s immature digestive system to metabolize and absorb. While it is also true that cow's milk contains less fat and less lactose compared to maternal milk, the significant point is that the proteins are difficult to digest for puppies, just as they are for human infants.
Different from cow's milk, colostrum is very important for newborn mammals, including puppies, as it helps boost their immune system and provides essential nutrients during the first days of life prior to the transition to more mature milk.