Growth and morphological changes in the stomach of newborn pigs during the first three days after birth

Growth and morphological changes in the stomach of newborn pigs were examined during the first 3 days after birth. The stomach grew disproportionately faster than the body as a whole during this period. The growth was due to hyperplasia and hypertrophy during the first day and mainly to hyperplasia thereafter as gastric DNA content increased progressively after birth, and the protein:DNA and RNA:DNA ratios increased only on the first day. Histological and morphometric analyses revealed that the growth was more pronounced in the gastric body region than in the cardiac and pyloric regions, and more pronounced in the mucosal layer than in other layers. The percentage of mucosal volume occupied by parietal cells (volume density) and the number of parietal cells per unit volume of gastric mucosa (numerical density) increased significantly 3 days after birth in the cardiac and body regions, but not in the pyloric region, of the stomach. The observed morphological changes coincide with the known pattern of functional maturation during the immediate postnatal period. It is suggested that a high level of circulating gastrin and oral ingestion of milk-derived growth factors in the newborn pig contribute to these changes.