This study was conducted to evaluate the effects of processed apple peel waste (APW), alone or in combination with an enzyme, as a natural antioxidant on broiler chickens under heat stress. A total of 360 unsexed, 28-day-old broilers were assigned to 6 dietary treatments with four replicates (15 broilers per pen). The experiment consisted of a 3 ×2 factorial arrangement with three levels of apple peel waste (0, 50 or 100 g/kg of diet) and two levels of enzyme (0 or 500 mg/kg, ZY Multi®). Inclusion of 100-g APW/kg of diet decreased broiler weight gain at 42 days of age. Inclusion of 50 and 100-g APW/kg of diet increased gizzard and small intestine weights. Feeding 50 and 100-g APW/kg increased highdensity lipoprotein (HDL) cholesterol and decreased lowdensity lipoprotein (LDL) cholesterol and malondialdehyde in blood serum at 49 days of age. At 49 days of age, apparent ileal protein digestibility was reduced when 50 and 100-g APW/kg were used in the diet. This study showed that feeding APWup to 50 g/kg from 28 to 49 days of age increased HDL cholesterol and decreased LDL cholesterol in serum and had no adverse effect on broiler performance.
