The development of a circadian pattern of salivary cortisol secretion in the neonatal piglet.

Saliva was collected from neonatal piglets in order to assess the secretory dynamics of cortisol in the newborn piglet. Saliva was collected from two litters of piglets (n = 16) from multiparous sows at 07.00, 11.00, 15.00 and 19.00 h on days 0, 1, 2, 4, 6, 10, 14, 18, 22, 26 and 30 post partum. Salivary cortisol concentration was determined by radioimmunoassay. Salivary cortisol concentration was high perinatally and declined with age. The frequency of escape attempts and vocalisation intensity during collection, as well as the similarity in salivary cortisol concentration on day 22 in control piglets and piglets that had provided samples repeatedly from day 0 suggested that this was not an adaptive response. A circadian pattern was evident in female pigs from day 6, whereas males displayed a similar pattern from day 10. The collection of saliva in the piglet provides a viable alternative to blood sampling for the assessment of a glucocorticoid circadian rhythm. Copyright 2002 S. Karger AG, Basel