Association between oestrogen receptor β immunoexpression and cause of culling, ovarian appearance and the existence of PRRS virus in the porcine ovary

The objective of this study was to determine the immunoexpression of oestrogen receptor beta (ERβ) in the gilt ovary and its association with cause of culling, ovarian appearance and the existence of porcine reproductive and respiratory syndrome (PRRS) virus in the ovary. In total, 62 ovaries were collected from culled replacement gilts. The gilts were classified according to the cause of culling (abnormal vaginal discharge, abortion, anoestrus, repeated service and non-reproductive causes), ovarian appearance (non-cycling and cycling) and the existence of PRRS virus in the ovary (not exist and exist). Ovarian ERβ expression was determined using immunohistochemistry. The proportion of ERβ immunostaining in the theca cells surrounding the follicles was evaluated using imaging software. The result revealed that ERβ immunostaining expressed in the theca interna cells of the follicles in the gilt ovary. The ERβ immunostaining was detected in 23.7 ± 19.8% (range 0–98.4%) of the theca cells. The gilts culled due to anoestrus had lower ERβ immunostaining (19.3%) compared to those culled due to non-reproductive causes (28.9%, P = 0.010) and repeated service (31.3%, P = 0.008). However, the expression of ERβ in the ovarian tissues with and without PRRS virus existence was not different (26.8 and 25.2%, respectively, P = 0.538). Likewise, ERβ immunoexpression in the follicles of non-cycling and cycling ovaries was not different (25.8 versus 26.3%, P = 0.851). In conclusion, the gilts culled due to anoestrus had relatively poor ovarian ERβ immunoexpression. Neither the existence of PRRS virus nor ovarian appearance was associated with ERβ immunoexpression in the gilt ovary.