288 Plasma Concentrations of Cortisol During the Periparturient Period in Gilts

Abstract An increase in plasma concentrations of cortisol is one signal that begins parturition and uterine contractions in pregnant sows; however, it is not known whether a critical level of cortisol is necessary or the role that it may play in the duration of parturition. The objective of the study was to characterize plasma concentrations of during the periparturient period and assess its relationship with initiation of parturition, litter size, and farrowing duration. Blood was collected via indwelling catheters from 5 primiparous gilts twice daily (0700 and 1900 h) from d113 of gestation until the birth of the first piglet, after which blood was collected every 15 minutes until farrowing was considered complete. Time of birth of each piglet was recorded. Farrowing duration was defined as the time between birth of the first and last piglets. Plasma concentrations of cortisol were determined by radioimmunoassay. Litter size was 12, 12, 18, 17, and 14 piglets and farrowing duration was 72 minutes, 4.1, 6.7, 5.8, and 4 hours, respectively. Quadratic and linear regressions were performed using the RStats package in RStudio (version 1.2.5025). Serum concentrations of cortisol were 3.37 ± 1.55 and 5.73 ± 2.18 ng/mL prior to parturition and at the birth of the first piglet, respectively. There was a positive quadratic relationship (P ≤ 0.07) between time of birth of each piglet and plasma cortisol levels; peak cortisol was 14.45 ± 3.20 ng/mL. There was a positive correlation between initial cortisol level and average piglet birth weight (P = 0.0124) but no relationship with total litter weight (P > 0.05). Determination of the periparturient changes in cortisol may be useful in designing farrowing induction protocols.