Abstract
The study was aimed at the evaluation of the effects of breed, age, different digestion stimulators, and dietary crude protein (CP) level on the activities of proteolytic enzymes in pancreatic tissue and duodenal chymus (in vivo), serum trypsin and α1-proteinase inhibitor (A1PI) concentrations in meat-type chicks. The study of age dynamics of trypsin and A1PI concentrations was performed on the chicks of hybrid cross “Smena-8”and two parental lines (Plymouth Rock and Cornish) fed standard commercial corn-wheat-SBM diets. Twenty birds per breed were euthanized at 1, 7, 14, 21, 28 and 35 days of age to obtain blood samples and pancreatic homogenate. Experiments on the effects of different digestion promotors (probiotic, acidifier, phytobiotic, enzymatic preparation) and different CP levels (finisher diet, CP 20%, vs. ground corn, CP 8.5%) were performed on 12 hybrid chicks with fistulated duodenum from 14 to 50 days of age. The following conclusions were made: 1) At 1 day of age high proteolytic activity in pancreatic tissue and maximal serum concentrations of trypsin and A1PI were found in both hybrid and parental lines. Since 7 to 35 days of age A1PI concentration was nearly constant, serum trypsin concentration decreased while proteolytic activity in pancreatic tissue exhibited undulate increase; 2) Proteolytic activity in pancreatic tissue was higher in hybrids compared to the parental lines from 7 to 35 days of age (p 0.05); 3) Supplementation of diet with exogenous enzymes stimulated the digestion due to the increase in protease activity in duodenal chymus by 9.1% compared to unsupplemented control (p 0.05); 4) Proteolytic activity in duodenal chymus significantly responded to the substitution of ground corn for the complete diet by 2-fold decrease while serum trypsin concentration responded by 2.5-fold increase (p 0.001). This fact can indicate that physiological functions of digestive proteases are not confined to the digestive processes.
Highlights
The pancreas is a mixed gland performing both exocrine and endocrine functions: exocrine function is related to the production of digestive enzymes releasing within the pancreatic juice and entering the duodenum to hydrolyze essential dietary nutrients while endocrine function is related to production of hormones participating in metabolic regulation
Since 7 to 35 days of age A1PI concentration was nearly constant, serum trypsin concentration decreased while proteolytic activity in pancreatic tissue exhibited undulate increase; 2) Proteolytic activity in pancreatic tissue was higher in hybrids compared to the parental lines from 7 to 35 days of age (p < 0.05); 3) Supplementation of diet with exogenous enzymes stimulated the digestion due to the increase in protease activity in duodenal chymus by 9.1% compared to unsupplemented control (p < 0.05); 4) Proteolytic activity in duodenal chymus significantly responded to the substitution of ground corn for the complete diet by 2-fold decrease while serum trypsin concentration responded by 2.5-fold increase (p < 0.001)
Proteolytic activity in duodenal chymus significantly (p < 0.001) responded to low-protein diet by 2-fold decrease while serum trypsin concentration responded by 2.5-fold increase compared to high-protein diet (p < 0.001)
Summary
The pancreas is a mixed gland performing both exocrine and endocrine functions: exocrine function is related to the production of digestive enzymes releasing within the pancreatic juice and entering the duodenum to hydrolyze essential dietary nutrients while endocrine function is related to production of hormones participating in metabolic regulation. Laporte and Tremolieres [3] have suggested that this role can be related to the regulation of pancreatic enzyme secretion: the more circulatory trypsin concentration, the less amounts of enzymes will be secreted within the juice, and vice versa; trypsin regulating circulatory factor in their hypothesis was cholecystokinin CCK (pancreozymin). Some authors have suggested the existence of CCK-independent feedback regulation of pancreatic secretion mediated by intestinal trypsin in human [4]. Trypsinogen entering the duodenum within the pancreatic juice is activating to trypsin by duodenal enzyme enterokinase; in the intestine trypsin hydrolyzes proteins and peptides to amino acids (for subsequent absorption into the bloodstream and lymph) with partial absorption of trypsin itself into the serum where its activity will be inhibited with possible partial return of the inactivated trypsin into the pancreas
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