Nocturnal One-Hour Lighting Stimulates Gonadal Development and Lowers Fat Deposition in Male Mule Ducks

SIMPLE SUMMARY: Photoperiods can affect sexual maturity, body weight, and body composition. In this work, we provided male mule ducks with a one-hour lighting from 20:00 to 21:00, in addition to the natural photoperiod, and evaluated its effects on their body weight, organ mass, gonadal function, and plasma levels of metabolites. The results indicate that the nocturnal lighting stimulated gonadal development and function and reduced fat deposition. This implies that nocturnal lighting is able to shorten the feeding period for the marketing of mature ducks. ABSTRACT: In this study, the effects of a nocturnal light pulse on body weight, organ mass, gonadal function, and plasma levels of metabolites were determined in male mule ducks. In total, 32 15-week-old mule ducks were randomly allocated to either Group C (control group) or L+ (lighting group). Group C was exposed to the natural photoperiod, whereas Group L+ was provided with a 1-h lighting over 20:00–21:00 every day, in addition to the natural photoperiod. At the end of the 42-day experiment, Group L+ had significantly lower relative weights (% of live weight) of the digestive tract and abdominal fat and higher relative weights of the breast meat and testes than Group C. Moreover, Group L+ had significantly higher plasma testosterone and lower plasma glucose levels. However, no between-group differences were observed in the triacylglycerol and uric acid levels. Histological examination demonstrated that the seminiferous tubule diameter was larger in Group L+ than in Group C. Moreover, the meiosis stage in spermatogenesis had begun in Group L+ but not in Group C. In conclusion, the supplemented 1-h lighting at 20:00 stimulated gonadal development and function and reduced fat deposition.