[Objective] The aim of this paper is to find the change law of reproductive hormones of female swamp buffalo in off season for estrus and to investigate the relationship between various hormones. [Method] The concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH), inhibin (INH), estradiol (E2) and progesterone (P4) were determined by the enzyme-linked immunosorbent assay (ELISA) in off season for estrus. The changes of follicles in the estrous cycle were examined using B-mode ultrasonography. [Result] In off season for estrus of female swamp buffalo from Guangxi region, the blood concentration of E2 and P4 varied fluctuantly. The concentration of E2 had two peaks, respectively 3 d before ovulation and after 13 d post ovulation. The concentration of P4 increased slowly from the first day after ovulation, increased rapidly from 5 to 13 d, peaked on Day 16 and decreased to the baseline 3 d before ovulation. The concentrations of FSH, LH and INH reached a peak respectively after 10 d post ovulation, 2 d before ovulation, and after 4 d post ovulation. The changes of the hormones had correlations. The concentrations of FSH, LH and INH had highly significant correlations with each other, while the concentration of INH had highly significant correlations with that of E2 or P4. The concentration of E2 also had a highly significant correlation with that of P4. [Conclusion] The study can guide the breeding of swamp buffalo from Guangxi region and also help to improve their reproduction performance.
