DIGESTIVE PHYSIOLOGY OF THE PIG

The pig has a monogastric type digestive tube, which in the adult, is capable of enzymatic digestion and is completed by microbial digestion . This double system allows the pig to tolerate great diversity in its dietary regimens. The fact that there is distal fermentation compensa tes for insufficiencies in digestion performed in the anterior section s of the intestine. The origins of these insufficiencies can be: poor feed digestibility or a problem in the normal mechanisms of enzymatic digestion. Before weaning, the weak functional activity of the large i ntestine means that digestion is almost exclusively of enzymatic origi n. It is for this reason that pathological problems affecting the smal l intestine have repercussions on the volume and nature of the faeces. The mechanisms of digestion and absorption are dominated by the actio ns of the enterocytes, be it to perform the last stags of digestion (h ydrolysis of disaccharides and small peptides) or absorption (absorpti on of monosaccharides, absorption and resynthesis of lipids and absorp tion of amino acids and oligopeptides). Anything which affects the epi thelium results in poor digestion and/or malabsorption. The enterocyte s also produce intestinal secretions which can become uncontrollable w hen stimulated by enterotoxins, such as those produced by coli bacteri a. Piglets are predisposed to the problem of diarrhoea in the third we ek postnatally because there is a lack of pancreatic and intestinal en zyme activity. In addition, the colonisation by enterotoxigenic coli b acteria in this period is favoured by the aggressive nature of solid f eed. A hypersensitivity reaction seems to be frequent, but it is not i ndispensable nor systematic in the development of diarrhoea.