The effect of graded levels of melatonin on performance and gastric ulcers in pigs

To induce gastric ulcers, finely ground (578±1.89 µm), maize-wheat-based diets containing melatonin 0, 2.5, 5 and 10 mg/kg, were offered to 64 Yorkshire barrows and gilts (mean weight 22.2±2.0 kg) assigned to 16 pens (4 per pen), until they reached 105 kg. At postmortem, ulcers were scored from 0 (no ulcer) to 3 (severe ulcer). Volume, percent moisture, pH and bile acid concentration of stomach digesta were determined. Melatonin supplementation was associated with a decreasing severity of ulcers (P<0.05). There were no differences in average daily gain between melatonin treatments, although 10 mg/kg diet caused a reduction in feed intake. Bile acid levels in stomach digesta were highest in pigs fed on the melatonin-free (control) diet (P<0.05); pigs with severe ulcers had higher bile acid levels than those with no ulcers (P<0.05). The results showed that pigs supplemented with melatonin had significantly fewer ulcers and less severe ulcers than those not supplemented with melatonin.