Hormone profiles around weaning in cyclic and anoestrous sows

Peripheral plasma patterns of LH, cortisol, corticosteroid-binding globulin (CBG) and beta-endorphin were studied around weaning in sows that resumed cyclicity and those that remained anoestrus after weaning. Average LH concentration in both groups of sows, and basal LH concentration, LH pulses/6 h and the sum of LH pulses and peaks/6 h in the cyclic sows, increased from the day before weaning to significantly higher (P < 0.05) levels on the days after weaning. Overall, average and basal LH concentrations were higher (P < 0.05) in the sows that resumed cyclicity than in those that remained anoestrus. Cortisol and beta-endorphin concentrations were high before weaning and on the day of weaning in both groups of sows. Cortisol in the cyclic sows, and beta-endorphin in both groups of sows, decreased (P < 0.05) after weaning. CBG levels were unchanged until the second day after weaning when there was an increase (P < 0.05) in both groups of sows. Before and even after weaning cortisol, CBG and beta-endorphin levels tended to be higher in the sows that remained anoestrus compared with those that resumed cyclicity. Findings in the present study show higher levels of cortisol, CBG and beta-endorphin before weaning that persisted even after weaning, and lower LH concentrations around weaning in sows that failed compared with those that resumed oestrous activity.