Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/1996
Publication Date: N/A
Interpretive Summary: Reduction in the amount of salmonellae that colonizes the intestinal tract of commercial poultry can be achieved by providing newly-hatched chicks with cultures of normal intestinal microflora. This method of controlling salmonellae colonization is called competitive exclusion. Numerous researchers have developed different types of competitive exclusion cultures, but there are differences in the ability of these cultures to control salmonellae. One problem in comparing different cultures is the lack of a biological assay that is a direct result of culture treatment and is correlated with decreased intestinal colonization by salmonellae. Recently in our laboratory, we have shown that administration of bacterial cultures to newly-hatched chicks rapidly increases the number of bacteria and the amount of propionic acid in the gut. In this study, we developed competitive exclusion cultures by several different methods to determine if propionic acid is associated with salmonellae control by all protective cultures. Eight different competitive exclusion cultures were developed by different techniques. Cultures that increased intestinal propionic acid in baby chicks decreased salmonellae colonization. Cultures that failed to increase intestinal propionic acid concentration in baby chicks did not protect against salmonellae colonization. The results of these experiments are important to the poultry industry and the scientific community because it will allow different competitive exclusion cultures to be compared based on a biological parameter resulting from culture treatment and shown to be correlated with the reduction of intestinal salmonellae colonization.
Technical Abstract: Experiments were conducted to evaluate the effects of different types of competitive exclusion (CE) cultures on the concentration of cecal propionic acid in 3-day-old broiler chicks, and the correlation, if any, between cecal propionic acid and protection against cecal Salmonella colonization. CE cultures developed by continuous-flow (CF) culture that significantly (P<0.05) increased cecal propionic acid in 3-day-old chicks and a undefined CE culture that significantly (P<0.05) increased cecal propionic acid concentration in 3-day-old chicks also significantly (P<0.05) decreased cecal Salmonella colonization in 10-day-old chicks compared to the untreated controls. CF cultures that failed to significantly (P>0.05) increase cecal propionic acid concentrations in 3-day-old chicks also failed to significantly (P>0.05) protect against cecal Salmonella colonization in 10-day-old chicks compared to untreated controls. A significant (P<.05) correlation (-.88) was found between cecal propionic acid concentration in 3-day-old chicks and cecal Salmonella colonization in 10-day-old chicks. Although the relationship between cecal propionic acid concentration and protection against cecal Salmonella colonization is not understood, it appears that it is a biological parameter resulting from treatment with a efficacious CE culture that is highly correlated with Salmonella protection, and therefore may serve as a standard measurement for comparing efficacy of different CE cultures.