Not every litter contains a runt. A runt puppy is considerably smaller than his littermates and often prone to health issues. However, that doesn't mean a runt puppy can't grow up to be a happy, healthy, normal-sized dog. Some animal shelters and pet adoption groups find that many people are drawn to the runt because he appears so cute and needy.
Runts often develop in the middle of their mother's uterus, which is shaped like a Y. They're the furthest away from mama's blood supply, so receive less nourishment than the other puppies sharing the womb. While runts have a rough start in life, with proper care and, barring major health issues, they can grow up just fine and live a normal lifespan.
Mother's first milk contains colostrum, a rich fluid ripe with antibodies to protect newborns. If the runt can't get to the colostrum and reap its benefits, he'll lack protection from common puppy maladies. Lack of colostrum can mean early death for pups, so if the runt in your litter didn't get a sufficient amount, purchase puppy milk replacer containing colostrum and contact your vet for advice. Runt puppies are also prone to weak bones. Your vet can recommend supplements to aid this issue.
Some mothers ignore and won't feed the runt, along with any puppies born with a deformity. While that might be nature's way of weeding out the weak, you can give that runt a fighting chance. If mama dog rejects him, you'll either have to feed Runty Pup a commercial puppy milk replacer or find another mother dog to let him nurse. Sometimes, the mother dog won't even bother to break a runt puppy's amniotic sac after birth. It becomes the job of any person on hand at the delivery to do the deed. After gently removing the sac, wipe the puppy's face with a warm washcloth so he starts breathing. Rub his body gently to aid in respiration.
According to Pound Ridge Veterinary Center, don't break the umbilical cord for about 10 minutes. After that, "the cord should be disinfected and severed by placing two ligatures of thread and severing between them leaving a 1 to 2 inch stalk attached to the puppy."
Just because the runt is the smallest, don't automatically assume he's also the most submissive. More than likely, he's turned out to be a scrapper, because otherwise he's bullied by his siblings or can't get his share of mom's milk. Runts kept in the litter have to learn how to protect themselves pretty early on. He could easily turn out to be the most outgoing, dominant puppy in the group.
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