Institution: University of Maryland
Principal Investigator: Dr. Shawna Weimer
University of Maryland
Department of Animal and Avian Sciences
8127 Regents Dr.
College Park, MD 20742
The prevalence of Salmonella in broiler flocks and products is an important production, food safety and human health concern. Colonization of Salmonella in the chicken gastrointestinal tract can be affected by many physiological and environmental factors such as age, genetics, nutrition, gut health, environment, stress and management. However, research is needed that focuses on the contribution of broiler genetics to the gut microbiome or to pathogen resistance.
Gut microbiota stimulate digestive tract development and impact nutrient digestion, digestive enzymes and gut mucosal proliferation. It also plays an important role in the control and resistance of pathogen colonization. Some human health research has identified the substantial impact of host genetics on the gut microbiota and the direct affect gut microbiota have on the innate and adaptive immune responses. In chickens, genetic selection and gut microbiome modulation methods have been identified to enhance Salmonella resistance. Due to both the commensal nature of most Salmonella strains in the gut and the stoic nature of broilers, birds carrying Salmonella do not show clinical signs of illness. However, subclinical physiological and behavioral indicators may exist. The links connecting the genotypic to phenotypic relationships with the gut microbiome and the immune response to pathogens in broilers remain relatively nebulous.
The objective of this study was to evaluate the differences in immune response, gut morphology and microbiome, and behavior of fast- and slow-growing broiler chickens challenged with Salmonella Typhimurium.
Overall findings showed that breed had a much stronger effect than Salmonella challenge. Salmonella did induce a small variety of responses, including impaired intestinal morphology in fast-growing birds at 24 days and elevated IgA concentrations at 21 days in the slow-growing birds. The fast-growing birds were heavier, had greater jejunum gut integrity, and greater concentrations of immunoglobulins IgA and IgG in blood plasma by 24 days. Slow-growing birds had greater IgG concentrations at 7 days and their gut integrity was more resilient to challenge by 24 days. Behaviorally, fast-growing broilers were less exploratory, social and aggressive than slow growing. Birds from both breeds and challenge treatments sat more and stood less on days 16 and 20 after challenge, which the researchers hypothesize could have been due to the stress of subjection to oral gavage.
The results of this study indicate that meaningful genotypic and phenotypic differences exist between fast- and slow-growing broiler body weight, immune response, gut morphology and microbial communities, and behavior when challenged with Salmonella Typhimurium. Delineating the differences in basal and Salmonella-challenged phenotypes of broilers with divergent growth rates provides useful information for genetic, nutritional and management decisions.
