Changes in oestrous cyclicity following olfactory bulbectomy in post-pubertal pigs

Area of Science:

• Reproductive Endocrinology
• Neuroendocrinology
• Animal Science

Background:

• Bilateral olfactory bulbectomy (OBX) in post-pubertal gilts can disrupt reproductive cyclicity.
• Seasonal patterns of anoestrus have been observed in OBX gilts, particularly during summer and autumn.

Purpose of the Study:

• To investigate the effects of olfactory bulbectomy on oestrous cycles in gilts.
• To explore the role of olfactory cues and photoperiod in mediating these effects.
• To understand the underlying neuroendocrine mechanisms.

Main Methods:

• Surgical bilateral olfactory bulbectomy in 16 post-pubertal gilts over two years.
• Housing OBX gilts with or without boars (intact or vasectomized).
• Monitoring oestrous cycles, plasma hormone levels (oestrogen, progesterone, LH), and ovulation.
• Comparing OBX gilts with unoperated controls.

Main Results:

• OBX gilts exhibited prolonged periods of anoestrus (inactivity of oestrous cycles), especially during summer and autumn.
• Exposure to intact boars or relocation to different pens restored oestrous cycles in some OBX gilts.
• Anoestrus was associated with low oestrogen, progesterone, and LH levels, indicating a lack of ovulation.
• Gonadotrophin treatment did not consistently restore oestrus in all OBX gilts.
• Unoperated gilts maintained continuous oestrous cycles.

Conclusions:

• Olfactory bulbectomy significantly disrupts oestrous cycles in gilts, leading to seasonal anoestrus.
• The effects appear to be mediated at the hypothalamic level.
• Seasonality of anoestrus in OBX gilts is likely due to the unmasking of photoperiodic influences.
• Olfactory cues and environmental changes can partially reverse the effects of bulbectomy.