The effects of continuously or diurnally fed melatonin on broiler performance and health

An experiment was designed to investigate the effects of dietary melatonin (MEL) on the performance and health of broiler chicks. Chicks raised under constant lighting were fed practical broiler diets in mash form containing 0, 20, or 40 ppm MEL from 0 to 3 wk. A fourth treatment (0 ppm MEL: 6h/d; 20 ppm MEL: 18 h/d) was used to mimic a diurnal light:dark cycle. Commercial broiler grower diets without MEL supplementation were fed from 3 to 6 wk of age. A small dose-related decrease was observed in weight gain (0 to 14 d) and feed consumption (0 to 21 d) due to continuous feeding of MEL. Continuously fed MEL also improved feed efficiency in the first 3 wk vs the control (0 ppm). Growth and feed consumption from 0 to 21 d were not affected by the diurnally fed diet when compared with the control treatment. No effects were found for mortality. However, the incidence of sudden death syndrome (SDS) was numerically less for the diurnal (3.56%) and 40 ppm (3.76%) diets from 0 to 42 d than for the control treatment 5.56%. Skeletal disease was generally unaffected, with the exception of the incidence of crooked toes at 42 d (0 ppm MEL: 8.67% vs diurnal: 4.89%). Dietary MEL fed either continuously or in a diurnal pattern had a minor effect on the performance and health of broiler chickens.