GENETIC-STUDY OF BEHAVIORAL AND PITUITARY-ADRENOCORTICAL REACTIVITY IN RESPONSE TO AN ENVIRONMENTAL CHALLENGE IN PIGS

The adaptive response to environmental challenges involves both behavi oral and neuroendocrine adjustments, and genetic factors have been sho wn to partly determine the intra- and interspecific variability observ ed in stress responses. To gain access to the biological and genetic b asis of this variability, differences in neuroendocrine and behavioral responses to a 10-min novel environment exposure were studied in Meis han (MS) and Large White (LW) pig breeds, as well as in their F1 (MS x LW), F1R (LW x MS), and F2 (F1 x F1) crossings. Different behavioral scores were recorded and blood was taken by venipuncture, before and a fter the test, to measure Levels of stress hormones (adrenocorticotrop ic hormone: ACTH and cortisol). MS pigs exhibited low vocalization, lo comotion, and defecation scores when compared to LW. F1s showed interm ediate locomotion scores. The vocalization scores of F1s were not sign ificantly different from the respective scores of their parental MS an d LW breeds. The defecation scores in F1s showed that there was some d egree of dominance in the MS direction. Basal and poststress cortisol levels were higher in MS, F1s, and F2 than in LW, suggesting the domin ance of this trait. Basal ACTH levels did not differ between the genet ic types, whereas LW displayed higher poststress ACTH levels than MS. Phenotypic correlations were analyzed in the F2 segregating cross to s tudy a possible link between behavioral and neuroendocrine traits. All behavioral variables were intercorrelated with 3 levels of associatio n. The correlations between vocalization and locomotion scores and pos tstress ACTH levels suggest that these measures reflect the level of r eactivity to the environmental challenge, and that they may share a co mmon genetic control. (C) 1997 Elsevier Science Inc.