Effect of heat stress on Salmonella infected broilers

Brazilian researchers have published a paper investigating the effects of heat stress on broiler chickens already infected with Salmonella. They find that the combination of both a Salmonella infection with heat stress disrupts the intestinal barrier, allowing the bacteria to infiltrate the gut, contributing to a decrease in performance parameters.

Stressful situations reduce the welfare, production indices and immune status of chickens. Salmonella spp. are a major zoonotic pathogens that annually cause over 1 billion infections worldwide. The experiment analysed the effects of 31±1°C heat stress (HS) (from 35 to 41 days) on performance parameters, Salmonella invasion and small intestine integrity in broiler chickens infected with Salmonella Enteritidis.

Heat stress decreased body weight gain and feed intake. However, feed conversion was only increased when HS was combined with Salmonella Enteritidis infection.

In addition, all heat stressed birds showed an increase in serum corticosterone levels with a hypothalamus–pituitary–adrenal axis activation. Furthermore, mild acute multifocal lymphoplasmacytic enteritis, characterized by foci of heterophil infiltration in the duodenum, jejunum and ileum, was observed in the HS group.

In contrast, similar but more evident enteritis was noted in the heat-stressed and Salmonella-infected group. In this group, moderate enteritis was observed in all parts of the small intestine.

Lastly, Salmonella counts in the spleens of the stressed and Salmonella-infected chickens were increased. The combination of HS and Salmonella Enteritidis infection may therefore disrupt the intestinal barrier, which would allow pathogenic bacteria to migrate through the intestinal mucosa to the spleen and generate an inflammatory infiltrate in the gut, decreasing performance parameters.

Source: Avian Pathology