Development and Adaptation of Protein Digestion

Abstract

Protein digestion is a complex process in which most aspects have a developmental pattern of activity. Gastric pH and intestinal peptide and amino acid transport as well as the activities of pepsinogen, trypsin, chymotrypsin, enterokinase and intestinal dipeptidases vary during development. No one species has been assessed for all these aspects and it is not possible to present an integrated developmental view of protein digestion. The following developmental changes, however, have been observed. Gastric pH declines, and peptic and pancreatic proteases exhibit increasing activity in pigs and rats after birth. The increase in pigs is gradual over several weeks starting at birth, whereas the increases in the rat begin at 2 wk, just prior to the time of weaning. The activities of dipeptidases in the rat and pig, peptide transport systems in the guinea pig and rabbit and amino acid transport systems in the rat, rabbit, guinea pig and chicken, however, appear (with few exceptions) to be active in the small intestine at the time of birth. Frequently, these activities peak in the neonate and decline during the postnatal period. In the rat, dietary protein tends to increase the activities of pancreatic proteases and intestinal peptidases and to increase the rate of uptake of amino acids by the intestinal epithelium. Individual dietary amino acids also influence amino acid transport systems. The data indicate that most processes in protein digestion undergo marked changes during prenatal and postnatal development and are influenced by the level of feeding and composition of the diet.

Broiler adaptation to post-hatching period

“…High-protein diet increased amino acid absorption rate in intestine but, effect degree ranged according to amino acid type (AUSTIC, 1985).…”

Organ-Specific Changes in the Expression of Mannose-6-Phosphate Receptors during Postnatal Development in Rats

“…By the first week after birth, it is possible that ␤ Nag and ␣ Man may use alternative routes for selective transport to lysosomes and that MPRs mostly correlate with another set of enzymes (such as procathepsin D and B) in the developing pancreas. It is known that, in general, proteolytic activity is present in the pancreas at the time of birth and that the levels of activity increase progressively into adulthood, although at different rates in different species [Austic, 1985]. Thus, the increase in both MPRs in this organ during development could be related to the increase in the proteolytic activity.…”

Efeito da Proteína Bruta e de Diferentes Balanços Eletrolíticos das Dietas Sobre o Desempenho de Frangos no Período Inicial

“…Embora o desempenho não tenha sido alterado pelo nível de PB na ração, (Austic, 1984), revisando vários aspectos sobre o desenvolvimento e a adaptação da digestão das proteínas, observou que muitos processos envolvidos neste metabolismo sofrem alterações marcantes durante o desenvolvimento pós-natal, sendo influenciados pelo nível de alimentação e a composição da dieta. Segundo Noy & Sklan (1995) a digestão dos produtos nitrogenados no intestino delgado aumenta de 78% no 4 o dia para 92% no 21 o dia.…”