The role of exocrine pancreas for feed intake and growth. Studies in a model with exocrine pancreatic insufficient young pigs

Abstract: Exocrine pancreatic insufficiency (EPI), resulting from disease (e.g. cystic fibrosis, chronic pancreatitis) or surgery (e.g. pancreectomy or pancreas duct ligation), leads to disorders in the digestive system, such as, maldigestion, malabsorption and finally malnutrition. Pancreatic duct-ligated (PDL) pigs have been used as a suitable large-animal model to study the conditions and treatment of EPI. The main objectives of this thesis were to highlight the role of the exocrine pancreas in the growth and performance of young mammals. For that reason the EPI-pig model was evaluated and tested. The results showed a difference in the response to induced EPI by duct-ligation of different-aged pigs. Pigs that underwent PDL at an age of 7 weeks showed arrested growth, while pigs that underwent PDL at 16 weeks showed normal growth. Dietary supplementation with a porcine pancreatic enzyme preparation (PEP) restored growth of pigs. Moreover, dietary supplementation with PEP stimulated feed intake and growth in un-operated pigs. To evaluate the role of the exocrine pancreas for nutrient utilization, pigs were infused with an elemental diet (mimicking a digested diet) either alone or with oral PEP supplementation. Although the elemental diet was sufficient in maintaining normal growth in intact pigs, EPI-pigs showed growth arrest even the elemental diet was given. However, oral PEP supplementation partially restored the growth of these EPI-pigs infused with the elemental diet. This indicates that the exocrine pancreas, in addition to its digestive function, affects nutrient utilization by improving anabolism in young rapid-growing pigs. The changes of the gut in EPI pigs were manifested by increased intestinal permeability and increase of mucin-producing cells in jejunum. Moreover, in pigs duct-ligated at 7 weeks of age the gut morphology showed decrease of stomach mucosa in fundus and atrophy of the intestinal mucosa, while gut morphology of older pigs, ligated at 16 weeks of age, were similar to un-operated intact pigs. These results suggest that intestinal absorptive capacity was reduced in younger, but not in older EPI pigs. However, the brush border disaccharidases activities and non-pancreatic hydrolases-like activities in the small intestine were similar in both of these groups. In addition, the gut-associated lymphoid tissue appear to enhance only in older EPI pigs In conclusion, the EPI pig model conclusively shows the important role of exocrine pancreatic function for performance of fast-growing animals. The exocrine pancreas function is indispensable in early life but its importance decreases with age. Apart from the digestive function, the exocrine pancreas plays an essential role in post-absorptive nutrient utilization in young pigs. The compensatory mechanisms to EPI and capacity to digest and absorb the diet are age-related and appear to depend on the maturity of the gut.