Effects of grinding intensity and pelleting of the diet – fed either dry or liquid – on intragastric milieu, gastric lesions and performance of swine

• The effect of water content and feed structure on intragastric milieu of pigs was studied.
• Water content of offered diet did not influenced intragastric milieu.
• Finely ground and pelleted diet caused a liquid gastric content without pH gradients.
• Coarsely ground meal diet resulted in a dry, firm and stratified gastric content.
• Finely ground pelleted diet impaired epithelium of pars nonglandularis.

The risk of pigs developing gastric ulcers is higher when fed finely ground and pelleted diets, the supposed mechanism being the liquid gastric digesta – resulting in a consistent pH level in all areas of the stomach. In order to better understand the mechanisms involved in the higher incidence of impaired epithelium of pars nonglandularis (PN) after intake of finely ground and pelleted diets, the present study aimed at generating detailed information regarding the local intragastric milieu in pigs. In addition, the effects of the water content of the offered diet on dry matter (DM), pH, buffering capacity (BC) and chloride (Cl) content of gastric digesta of pigs were investigated as several studies had implied that a liquid gastric digesta is a major risk factor for the development of gastric ulcers in pigs. Both diets (coarsely ground fed as meal (CM) vs. finely ground, pelleted (FP)) were identical in botanical and chemical composition and were either offered dry or in liquid form (250 g DM/kg) ad libitum to 24 piglets. Weight gain and gain:feed ratio were not affected by the grinding intensity of the diet (P>0.05). However, a higher daily feed intake (P=0.015) and weight gain were observed in pigs fed liquid diets (P=0.009). After six weeks the animals were slaughtered and samples of gastric digesta were taken from different areas (pars nonglandularis, fundus, cardia and pylorus). The moisture content of the diet did not influence the pH (P≥0.1), whereas the structure of the diet (particle size and form of compaction) had a significant effect on the pH in the fundic area (P≤0.001). The FP diet caused a more liquid digesta (P≤0.05) in most areas and very homogenous pH values within the gastric digesta of different regions. In contrast, CM resulted in marked differences in the pH (P<0.05) in different areas with the highest values at PN and the lowest values at the fundus. None of the pigs fed CM showed gastric ulcers while the score of macroscopical evaluation of the epithelium at the PN was higher in pigs fed FP (P≤0.001) regardless of whether diets were fed dry or liquid. The BC at the PN was lower (P≤0.001) while Cl content at PN was higher (P≤0.001) in pigs fed FP. Particle size distribution of the diet seemed to be the predominant factor for intragastric milieu, while the moisture content of the offered diet had no effect (P>0.05) on observed parameters.