Effects of different rearing systems on the development of uropygial gland in three goose breeds

This study aimed to investigate and compare the age-dependent effects of net-floor mixed rearing system (MRS) and cage rearing system (CRS) on the development-related parameters of uropygial glands among three economically important goose breeds, including Sichuan White goose (SW), Gang goose (GE), and Landes goose (LD). All goslings were reared under the similar environmental conditions during the first 10 post-hatching weeks, and the goslings of each breed were then equally divided into the MRS and CRS groups. At weeks 30 and 43, eight geese from each experimental group per breed were randomly selected for morphometric and histological measurements of the uropygial glands, including Hematoxylin and Eosin (H&E) and oil red O-staining. The morphological results revealed that compared to CRS, the uropygial glands of SW and GE in MRS were better developed while those of LD were less developed at week 30; however, the uropygial glands of SW and GE in MRS developed weaker while those of LD developed better at week 43. Through histological observations, the effects of the rearing system and breed on the development of Zones I, II, and III in the goose uropygial glands were analyzed. Compared to CRS, the luminal thickness of Zone II of LD in MRS developed better while the tubular area of Zone I of GE developed weaker at week 30. At week 43, the uropygial glands of SW and GE developed weaker in MRS than in CRS, as reflected by the larger tubular area of Zone I and luminal thickness of Zone II in SW as well as the larger tubular area of Zone I in GE (P < 0.05). In contrast, the uropygial glands of LD developed better in MRS than in CRS, as reflected by the larger tubular area of Zone I and luminal thickness of Zone II in MRS (P < 0.05). Furthermore, the results from oil red O staining showed that the lipid droplet area and relative lipid droplet area percentage of Zone III in LD and GE were consistently higher in CRS than in MRS (P < 0.01). Also, under either CRS or MRS, the lipid droplet area and relative lipid droplet area percentage of Zone I and III were higher in LD and GE than in SW (P < 0.05). The correlation analysis showed that although the H&E- and oil red O-stained histological parameters of the goose uropygial glands were significantly affected by the rearing system, almost all of them exhibited similar correlations, as suggested by the observed positive correlations between the lipid droplet synthetic capability of Zone I and the lipid droplet storage of Zone III. In conclusion, the two rearing systems show both the age- and breed-dependent effects on the goose uropygial gland development and lipid deposition capacities, but the underlying regulatory mechanisms await further investigations.