AUSWIRKUNGEN DER FUTTERSTRUKTUR (VERMAHLUNGSGRAD, KONFEKTIONIERUNG) AUF MORPHOLOGISCHE UND IMMUNOLOGISCHE PARAMETER IM MAGEN-DARM-TRAKT VON SCHWEIN UND GEFLUGEL

摘要

Since decades, animal nutritionists are dealing with the ideal grinding intensity of diets for pigs and poultry, mainly in terms of digestibility. Generally, the basic principle "as fine as possible, as coarse as necessary" has been applied (e.g. regarding the development of gastric ulcers in pigs), but nowadays the trend rather heads for "as coarse as possible, as fine as necessary". With this background, several studies have already shown that digestibility is not negatively influenced when whole grains are included in diets for poultry. In pigs, however, at least moderate grinding of cereals is necessary to warrant appropriate utilisation of nutrients (preceacal digestibility). The higher nutrient utilisation of whole grains by poultry is probably due to efficient grinding processes in the gizzard. Thus, positive effects on gut health may - in contrast to pigs - not be caused by particle size distribution in the chyme per se, but by the higher activity of the gizzard and physiological processeslinked to this. In connection with higher muscular activity of the stomach/gizzard after offering coarsely ground feed/whole grains also the weight of the gastric and gizzard wall increases both relatively and absolutely; there are no comparable effectsin the lower parts of the intestinal tract. In poultry, also an increase in pancreatic weight was observed when whole grains were fed. This is of interest since the lower pH in the stomach/gizzard contents after feeding coarsely ground cereals is raisedby pancreatic secretions containing buffering substances. Comparable effects can be applied for the higher dry matter content in the stomach of pigs ingesting a coarsely ground diet: the dry matter content in the chyme of the small intestine is quite similiar, regardless of feeding coarsely or finely ground diets. Altogether, there seems to be evidence for an increased pancreatic secretion in swine as well as in poultry after feeding coarser diets.The resorptive surface (surface enhancement by villi) in the small intestine is not markedly influenced by the physical form of the diet, neither in poultry nor in pigs. Contrary to this, a deepening of the crypts of 7 - 13 % in the hindgut of pigs can be observed due to a higher microbial production of butyrate related to increased amounts of starch in the digesta. Especially in terms of preventing oral/gastrointestinal infections and from an immunological point of view coarser grinding seems to bear advantages for the animal: firstly, a lower pH in the stomach/gizzard is more efficient in reducing counts of bacteria reaching the small intestine. Secondly, a functioning stomach barrier with low pH values enabling a high pepsin activity and linked to this a high protein digestibility has been shown to reduce allergic reactions to feed, since the proteolytic activity in the GIT modulates the structure of allergens/epitopes. Furthermore, a mucus layer with a high content of acid mucins protects the underlying epithelium better from adhesion and invasion of pathogens compared to a mucus layer consisting predominantly of neutral mucins. Additionally, after feeding finely ground diets there are significantly more mast cells (broiler) and IgA secreting plasma cells (pig) in the gut mucosa. Finely ground feed seems to stimulate the mobilization of these cell types, probably due to a more intensive antigen contact.