PROSTAGLANDIN F2-ALPHA-INDUCED NEST-BUILDING IN PSEUDOPREGNANT PIGS .1. EFFECTS OF ENVIRONMENT ON BEHAVIOR AND CORTISOL SECRETION

may be susceptible to stress when they are strongly motivated to nest- build in a space-restricted environment. This study aimed to explore w hether nest-building behaviour could be induced by prostaglandin F2 al pha (PG) administration to pseudopregnant gilts and to determine wheth er induced behaviour and cortisol output differed between animals chro nically placed in either farrowing crates or pens. Jugular vein cathet ers were placed on Day 39 of pseudopregnancy and blood samples collect ed daily from Day 40 to Day 48. On Day 42, gilts were either restricte d to farrowing crates 1.6 x 0.6 m with no straw (C: n = 11) or left in pens 2.8 x 1.74 m with straw (P: n = 11). On Day 47, blood and behavi our sampling was from 90 min pre-PG (Dinoprost; Lutalyse, Upjohn, Kala mazoo, MI) to 6 h post-PC. PG injection successfully induced nest-buil ding behaviour in P gilts within 15 min of injection. Penned gilts eng aged in more straw/floor-directed behaviour than C gilts (p < 0.01), w hereas attempts in C gilts seemed partial or incomplete. Conversely, C gilts showed increased (p < 0.05) amounts of fixture-directed behavio ur, whereas P gilts did not post-PG. For both groups, cortisol increas ed significantly (p < 0.05) post-PG compared to pre-PC values. Cortiso l concentrations in C gilts were significantly greater than in P gilts prior to and after PG (p < 0.05) on Day 47, whereas there were no sig nificant differences in concentrations of cortisol between C and P on other days. These results demonstrate that PG can induce nest-building behaviour in the absence of foetal signals. Whereas the pseudopregnan t gilt seemed to chronically adapt to the imposition of a farrowing cr ate, gilts subsequently attempting to nest-build showed increases in c ortisol output when compared to their penned counterparts, suggesting that a stress was imposed by the space-restricted environment. (C) 199 7 Elsevier Science Inc.