Influência da genética bovina na suscetibilidade ao estresse durante o manejo e seus efeitos na qualidade da carne

Abstract

This thesis is composed of four works that seek to characterize the temperament of two genetic groups and its influences in beef cattle production and meat quality produced in the South Area of RS. The first refers to the evaluation of the temperament in animals raised extensively, as well as the evaluation of the quality of the produced meat, through pH and cortisol levels. Forty were studied castrated males, of two genetic " groups Bos taurus taurus " and " Bos taurus taurus x Bos taurus indicus ". There was a positive linear association between the presence of zebu blood and reactivity. Weight gain was negatively correlated with the average behavior score. There was no difference among the genetic groups for weight gain. Significant differences for pH were detected among the genetic groups and temperament classes. The second work evaluated the temperament of 79 beef cattle maintained in confinement and divided in agreement with 8 degrees of Charolais x Nelore blood. There was a negative linear association between behavior score and genetic group. The increase of the participation of Charolais blood was associated with decreased behavior scores values. Animals with larger percentage of Charolais blood presented larger weight gain. Initial pH values in xvii the carcass increased as increased percentage of Charolais blood. They were not found differences for water retention capacity and plasmatic cortisol level. The third work characterized the temperament of bovine handled in an action ring. 1572 animals of two genetic groups (" Bos taurus taurus x Bos taurus indicus " and " Bos taurus taurus ") were evaluated. Crossbred animals presented larger values than European breeds for the entrance and movement in the action ring scores. The males presented smaller reactivity compared with the females for the entrance and movement scores. The fourth work evaluated the effect of the genotype of 163 crossbred and European steers extensively raised on their temperament. Indian pure presented larger reactivity to the handling. The genotype can influence the temperament, modulating the reactivity of the animals during handling activities, and, of this form, the their weight gain and quality of the meat.