Abstract
The gastrointestinal tract plays an important role in studies of avian ontogenies because of its key function in nutrient intake. The pattern of intestinal development during postnatal growth in domestic pigeons (Columba livia), as an altricial bird, would be different from the pattern observed in precocial poultry. In this study, the intestinal morphology, mucosal enzyme activities, and pancreatic enzyme activities were determined from hatch to 14 d of age in pigeons. Rapid morphological development was observed immediately after hatching. Villus area and crypt depth increased in parallel in the duodenum and jejunum and more slowly in the ileum. Mucosal enzyme activities per gram of duodenum, jejunum, and ileum varied significantly with segment and age. There were also intestinal segment × age interactions, in which enzyme activity increased most dramatically in the jejunum as compared with the duodenum and ileum for sucrase and maltase activity from day of hatch to 8 d, and for alkaline phosphatase activity through 14 d. However, aminopeptidase-N activity increased most dramatically from day of hatch to 3 d in the ileum as compared with the duodenum and jejunum. Changes in carbohydrate-digesting enzymes activity in duodenum, jejunum, ileum, and pancreas are more pronounced than for protein-digesting enzymes activity from 3 d after hatching. Intestinal total enzyme activities exhibited a steady increase, which was highly correlated with BW. Pancreatic enzymes indicated patterns somewhat similar to those for intestinal enzymes. It was concluded that development of the absorptive area and the capacity for hydrolysis in the duodenum, jejunum, and ileum was rapid immediately after hatching, although rates of development were different in the 3 segments. Young pigeons differ from poultry, in whom intestinal and pancreatic digestive enzyme activities per gram of tissue are generally constant or decline during postnatal development. Also, the data seem consistent with the idea that intestinal hydrolysis may be a determining step in digestion and hence growth.