Background
As potential substitutes of traditional free-range rearing, floor rearing system (FRS) and net rearing system (NRS) are currently predominant dryland rearing systems. In this study, a total of 720 Nonghua ducks were assigned to a 2 × 3 factorial arrangement with two rearing systems (FRS and NRS) and three ages (4w, 8w, and 13w) to study the effects of FRS and NRS on production performance, antioxidant capacity and immune status.
Results
The production performance was mainly affected at 8w. Body weight, average daily gain, eviscerated weight and semi-eviscerated weight were higher in NRS at 8w, but carcass yield was decreased at 8w and 13w (P < 0.05). Lipid deposition was enhanced in NRS with higher sebum and abdominal fat yield at 8w and 13w (P < 0.05). NRS resulted in the liver developmental retardation at 4w and decreased gizzard index at all ages (P < 0.05). Antioxidant capacity was not affected by rearing systems (P > 0.05), but a tendency of better antioxidant capacity in NRS at 4w was found, while glutathione peroxidase (GSH-Px) activity was higher in NRS at 13w (P < 0.05). Spleen and thymus were promoted in NRS and immune cytokines were extensively affected by rearing system (P < 0.05), exhibiting general higher profiles of IFN-γ, IL-1β, IL-4, immunoglobulins in NRS. Serum biochemical parameters (AST, ALT, and ALP) indicated NRS was better for liver health, and in liver, ALP was higher in FRS at 13w, while ALP and IFN-γ in 13w-FRS were both higher than 4w-FRS and 8w-FRS (P < 0.05).
Conclusions
Compared with FRS, NRS was conducive to production performance and duck liver health to some extent but it had defects in visceral organ development and lipid deposition. Though antioxidant capacity was not significantly affected, NRS ducks might have better antioxidant capacity at the early stage of breeding, while GSH-Px activity was increased for scavenging excess free radicals at the later one. NRS increased the levels of IFN-γ, IL-1β, IL-4, immunoglobulins in serum and promoted the development of thymus and spleen to improve duck immune function. These results revealed the physiological impacts of FRS and NRS on ducks and provided a reliable reference for rearing system selection.