How do newborn rats feed? - briefly
Newborn rats receive nourishment exclusively through «mother’s milk», which they ingest by suckling the dam’s nipples. Lactational feeding persists until weaning at approximately three weeks of age.
How do newborn rats feed? - in detail
Newborn rats are altricial mammals that rely entirely on maternal milk for nutrition during the first weeks of life. Immediately after birth, the dam’s mammary glands begin secreting a nutrient‑rich fluid containing high concentrations of proteins, lipids, lactose, and immunoglobulins. This composition supports rapid tissue growth and provides passive immunity.
Pups locate the nipples by following the scent of the dam’s fur and by tactile cues from the nest. Contact of the pup’s mouth with the nipple triggers a neuroendocrine reflex in the mother, resulting in milk ejection. Suckling sessions occur every two to three hours, each lasting from one to five minutes. The frequency gradually declines as the litter approaches the weaning period.
The neonatal digestive tract is adapted for milk consumption. The stomach is relatively large, and gastric acidity is low, reducing protein denaturation. Enzymes such as lactase and pancreatic lipase are present in sufficient quantities to digest lactose and milk fats. Absorption occurs primarily in the small intestine, where villi are densely packed to maximize nutrient uptake.
Weight gain provides a measurable indicator of successful feeding. Typical growth rates exceed 5 g per day during the first ten days, tapering to 3 g per day as the pups approach three weeks of age. At approximately 21 days, the dam begins introducing solid food, and the pups progressively shift from exclusive milk intake to mixed diets.
Environmental conditions influence feeding efficiency. Adequate nest temperature (≈ 30 °C) reduces metabolic demands for thermoregulation, allowing more energy to be allocated to growth. Litter size affects competition for nipples; larger litters may experience reduced individual milk intake, potentially slowing growth rates. Maternal behavior, including grooming and nest maintenance, also contributes to the stability of the feeding environment.