Heat stress impairs performance and induces intestinal inflammation in broiler chickens infected withSalmonellaEnteritidis

Abstract

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. We therefore designed the current experiment to analyse 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. We observed that HS decreased body weight gain and feed intake. However, feed conversion was only increased when HS was combined with Salmonella Enteritidis infection. In addition, we observed an increase in serum corticosterone levels in all of the birds that were subjected to HS, showing 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, we observed an increase in Salmonella counts in the spleens of the stressed and Salmonella-infected chickens. 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.

Overcrowding stress decreases macrophage activity and increasesSalmonellaEnteritidis invasion in broiler chickens

“…The results obtained reinforce the hypothesis that the decreased performance observed in stressed broiler chickens might be related to alterations in the HPA axis function via corticosterone release (Shini & Kaiser, 2008;Shini et al, 2009;Quinteiro-Filho et al, 2010, 2012a, 2012b. Moreover, the observed intestinal inflammation could lead to a decrease in nutritional absorption because of the presence of intestinal lesions and because of sickness-related behaviour by release of certain interleukins (i.e.…”

“…Other results obtained in our laboratory revealed that different stressors such as footshock, chemical stressors and individual housing decreased the macrophage activity in mice (Fonseca et al, 2002;Palermo-Neto et al, 2003Quinteiro-Filho et al, 2009;Costa-Pinto & Palermo-Neto, 2010). In broiler chickens, we observed that heat stress decreased the macrophage oxidative burst (Quinteiro-Filho et al, 2010); this finding was linked to the observed increase of Salmonella migration to the spleen of heat-stressed chickens (Quinteiro-Filho et al, 2012a). In our study, overcrowding stress increased the Salmonella Enteritidis invasion to the liver but not to the spleen of the stressed chickens.…”

“…Different types of stressors, including chemical stressors, prenatal stress, individual housing, inescapable foot shock and others, can activate the HPA axis in rodents (Costa-Pinto & Palermo-Neto, 2010). As in heat stress situations (Quinteiro-Filho et al, 2010, 2012a, the overcrowding stress increased the serum corticosterone levels in broiler chickens. This "stress" hormone can subsequently dysregulate immune responses and may be potentially harmful to the health of the organism.…”

“…Heat stress was linked to a decrease in immune activity in poultry and mammals, following invasion by pathogenic bacteria (such as Salmonella spp.) through the intestinal epithelium (Burkholder et al, 2008;Quinteiro-Filho et al, 2012a;Verbrugghe et al, 2012).…”

“…Welfare assessment studies in chickens have been traditionally conducted by observing their mortality, physiology, behaviour and health, with emphasis placed on a bird's leg health and walking ability (Ekstrand et al, 1998;Weeks et al, 2000;Kestin et al, 2001;Martrenchar et al, 2002;Shepherd & Fairchild, 2010). Welfare concepts are being expanded to include glucocorticoid hormone release, performance parameters, immunological functions and disease susceptibility Shini et al, 2010;Quinteiro-Filho et al, 2012a). Because of these findings, stressful situations-including inadequate housing conditions, overcrowding, environmental temperature extremes, nutritional deprivation and others-must be carefully considered in the practices of broiler chicken production (Dawkins et al, 2004;Hoerr, 2010;QuinteiroFilho et al, 2010;Lay et al, 2011).…”