Reactivity of Nellore steers in two feedlot housing systems and its relationship with plasmatic cortisol

Abstract

To evaluate reactivity to assess the temperament of Nellore steers in two feedlot housing systems (group pen or individual pen) and its relationship with plasmatic cortisol, 36 experimental units were observed five times at 28-day intervals of weight management during a 112-day feedlot confinement. A reactivity score scale ranging from 1 to 5 was applied when an animal was in the chute system. To the calmest animal, a reactivity score of 1 was ascribed and to the most agitated, 5. Blood samples were collected for cortisol analysis. No differences were found in reactivity and feedlot system. There was a relationship noted between reactivity and feedlot time in both housing systems (Pb0.01). There was a relation between reactivity and cortisol levels for group animals (P=0.0616) and for individual ones (Pb0.01). Cortisol levels varied among housing systems (Pb0.01). Feedlot time influenced the cortisol levels (Pb0.09 individual; Pb0.01 group) and when variable time was included, these levels changed, decreasing in the group pen and increasing in individual pens. The continuous handling reduces reactivity and plasmatic cortisol, and group pen system seems to be less stressfully than individual pens.