Investigation of Off-Season Breeding Effects on Egg-Laying Performance, Serum Biochemical Parameters, and Reproductive Hormones in Zhedong White

Off-season breeding is a method of encouraging animals through manual intervention to reproduce during the non-breeding season. The egg-laying period of the Zhedong white goose usually starts from September and ends in April of the following year. During the summer months from May to August, with long daylight hours and high temperatures, the white geese rest and do not lay eggs. This study explored the effects of off-season breeding on egg production performance, serum biochemical indicators, and hormone secretion in Zhedong white goose. The experiment was divided into normal breeding and off-seasonal breeding. The results suggested that the peak laying period lasted 3 months, and egg production was 15.62% higher than that in the control group in the off-season breeding group. The off-season breeding group had a 4.13% higher egg fertilization rate in November (laying period) than the control group, and the hatching rate of hatched eggs and fertilized eggs in the peak laying period was 2.77% and 2.3% higher, respectively, than the control group. The experimental group showed significantly higher serum P, ALB (albumin), TG (triglyceride), and TC (total cholesterol) levels; serum AST (glutamic oxalacetic transaminase) activity; and CREA (creatinine) and BUN (blood urea nitrogen) levels than the control group at different time points. The serum LH (luteinizing hormone), FSH (follicle-stimulating hormone), P4 (progesterone), and E2 (estradiol) levels were significantly higher in the off-season breeding group than in the control group. The serum T3 (triiodothyronine) and T4 (Tetraiodothyronine) levels were significantly higher in the off-season breeding group than in the control group at different points in the breeding cycle. The control group showed a significantly higher gene expression of GnRH (gonadotropin releasing hormone) in the hypothalamus; GnRH, FSH, and LH in the pituitary; and GnRH in the ovary and significantly lower gene expression of VIP (vasoactine intestinal peptide) and PRL (prolactin) in the pituitary than the off-season breeding group. Thus, the off-season breeding of Zhedong white geese may prolong the peak laying period and improve egg production performance, thus enhancing the economic benefits of goose breeding.