During their first months, puppies need extra nutrition for added energy and to assist in the growth of developing organ and muscle tissue. (precisepet.com)
A baby born later has more developed organs, and is better able to suck and feed. (health-and-parenting.com)
However, the constant activation of the body's stress response systems due to chronic or traumatic experiences in the absence of caring, stable relationships with adults, especially during sensitive periods of early development, can be toxic to brain architecture and other developing organ systems. (developingchild.harvard.edu)