Twelve gastric-cannulated litter-mate pigs were used to study secretion and proteolytic activity in the stomach of suckling and early-weaned pigs in relation to age and food intake. 2. Results demonstrate that from the first observation at day 8, piglets were able to secrete acid. pH and acid concentration did not change during the first 4 weeks of life. 3. Proteolytic activity was low during the first 2--3 weeks of life and rapidly increased thereafter. 4. Two phenomena differentiated suckling pigs from pigs given dry cow's milk: (1) a low buffering capacity the gastric contents, beginning 1 hr after feeding the dry cow's-milk formula, results in a low total acid concentration in the weaned pigs and (2) the increase in proteolytic activity in relation to the age is much more pronounced in the artificially-reared pigs. 5. These two phenomena are discussed and related to the formation of a hard casein clot in the stomach of the cow's-milk-fed pigs, which has a long retention time and stimulates gastrin release.
