THE EXOCRINE PANCREATIC FUNCTION IN CHICKEN (<i>Gallus gallus</i>L.)FED DIETSCONTAINING DIFFERENT INGREDIENTS
The ability of animal pancreas to adjust its exocrine function to the composition of a diet is still a controversial concept and open question. A bulk of experimental data is published to the present evidencing the ability of the pancreas to modify the composition of its secretion in accordance with the composition of the digested feed both in mammals (I.P. Pavlov, 1950; A.D.Sineshchokov, 1965) and poultry (P.P.Berdnikov, 1990; Ts.Zh.Batoev, 2001; V.G.Vertiprakhov, 2012). The supporters of the theory of non-parallel enzyme secretion argue that the pancreas can rapidly change enzymatic profile of the secretion in response to a change in the ingested feed composition (i.e., the ratio of protein, carbohydrates, and lipids). The problem of the pancreatic adaptation to feed composition for more effective digestion is especially urgent for intense commercial poultry production and highly productive commercial poultry crosses. The productive potential of these crosses cannot be effectively realized without detailed and comprehensive knowledge of the digestive function in poultry. There were the attempts of sampling of pure pancreatic juice by U.S. scientists (T.F. Degolieret al., 1999); however, their approach (cannulation of pancreatic ducts) did not find broad acceptance. The intestinal activity of the digestive enzymes is extensively studied in China (L.Q. Ren et al., 2012; H. Sun et al., 2013); however, their research did not elucidate the exact mechanism(s) of the adaptation of pancreatic secretion to feed quality. This paper was aimed at the investigation of exocrine pancreatic function in Hisex White chicken fed diets with different composition. The unique technique of transplantation of the pancreatic duct into the isolated duodenal section (allowing the collection of pancreatic juice during sampling periods and redirection of the juice into the duodenum at other times) enabled the sampling of pure pancreatic juice from live and healthy birds and the studying of its composition and changes induced by diet shifts. This technique of chronic fistulation provides new knowledge on the responses of enzymatic activity and chemical composition of the juice to the changes in diets. It was found that the pancreas can precisely adjust the enzyme-secreting activity to the composition of feed digested: large increase in dietary crude fat (by 20.8%) resulted in a 33.8 % increase in the pancreatic lipase activity as compared to the basal level in starved birds. A moderate increase in dietary crude protein (by 3.3%) and amino acids (by 2.1%) resulted in substantial increase in proteolytic activity in the juice (by 28.1%). The long-term adaptation of exocrine pancreas to a diet shift is related mostly to the basal levels of secretion, e.g. the basal level of lipase activity in pancreatic juice increases by 37.7% after the increase in dietary crude fat. The short-term adaptation occurs in postprandial periods and involves both complex-reflex and neurochemical phases of the regulation of enzyme-secreting activity, e.g. the increases in lipase secretion at these phases after the shift to higher dietary crude fat level were 46.6 and 93.7%, respectively. The concentration of total protein in pancreatic juice tended to increase in fed birds, in parallel to the increases in the secretion of individual enzymes.