Effect of feed particle size and dietary melatonin supplementation on gastric ulcers in swine

Gastric ulcers may be an underrecognized problem in the swine industry. An experiment was conducted to evaluate the effects of dietary melatonin supplementation and particle size on prevalence and severity of ulcers in growing pigs. Sixty-four Yorkshire barrows and gilts (29.5 +/- 1.0 kg) received either a finely ground (763 +/- 2.18 mu m) or a coarsely ground (953 +/- 2.29 mu m) corn-wheat diet, either with or without added melatonin (5 mg kg(-1)). One half of the pigs underwent endoscopic examination to assess the severity of ulcers on days 4 and 25. Growth performance and feed consumption were monitored throughout the experiment. All pigs were slaughtered on day 28, and ulcers were assessed postmortem. Endoscopy at the beginning of the experiment found that 53% of the pigs already had some degree of ulceration. Pigs fed the fine diet had greater average daily gain and average daily feed intake than pigs fed the coarse diet (P < 0.05), but particle size did not significantly affect prevalence of stomach ulcers. Melatonin supplementation increased the apparent digestibility of crude protein (P < 0.04) and dry matter (P < 0.08) of the diets and decreased the prevalence of ulcers (P < 0.05) but did not significantly affect growth performance. Pigs that received melatonin had higher levels of melatonin (P < 0.01) in most gastrointestinal tissues, with highest concentrations found in the stomach (P < 0.001). Pigs that did not have ulcers had a higher concentration of melatonin in the plasma and stomach than pigs with ulcers (P < 0.05). Melatonin may be useful in decreasing ulcers. Initial ulcer condition may be a significant source of variation in growth experiments.