| The addition of exogenous enzymes to poultry diets was investigated with respect to the growth of Clostridium perfringens, the etiologic agent for necrotic enteritis (NE). Initially corn and wheat-based diets with and without exogenous enzyme supplements were chemically and enzymatically digested. The resulting supernatants in combination with fluid thiogycollate broth (FTG) were inoculated with either cells or spores of C. perfringens and anaerobically incubated for 6 h at 40°C. Results indicated that supernatants prepared from diets containing exogenous enzymes had no effect on the proliferation or germination of C. perfringens. Supernatants, especially those prepared from wheat and without the use of the digestive enzymes, pepsin and pancreatin, contained the least number of germinated spores. In supernatants without FTG both vegetative cell growth (five-strain cocktail) and spore (three-strain cocktail) development decreased presumably due to nutrient limitation. Overall, growth of C. perfringens was higher in wheat-based supernatants compared to corn. The growth of C. perfringens cells and spores in jejunum and ileum digesta collected from broilers fed corn, wheat or flax-based diets with or without exogenous enzyme supplement was also investigated. Concomitant analyses for LAB, coliforms and Escherichia coli were performed in order to assess possible changes in the background population. Overall, clostridia cell levels decreased during incubation especially in jejunal digesta from broilers fed flax-based diet. However, results examining the effects of exogenous enzymes on growth of C. perfringens in various digesta were mixed. In wheat, the inclusion of dietary enzymes decreased clostridial populations by at least two fold. Clostridia populations also decreased in digesta inoculated with spores however, again no clear pattern could be established with respect to digesta type, GIT location and presence or absence of dietary enzymes. Spore germination, indicated by the number of survivors following heat treatment, appeared higher in jejunal digesta containing corn followed by flax. Overall, inclusion of exogenous enzymes appeared to result in a decrease in ail background groups, however, in the case of flax digesta the opposite effect was observed in both the jejunum and ileum. In the last part of the study, segments from the small intestine of birds fed either wheat or flax-based diets with and without exogenous enzyme were excised, ligated and inoculated with a C. perfringens spore cocktail. Results indicated that exogenous enzyme in both diets but particularly in flax, significantly reduced C. perfringens, however, the effects on spore germination were less clear. Spore germination in flax compared to wheat, however, was at least 1 log lower. LAB was significantly suppressed by the addition of enzyme supplement in wheat. Ail other background groups showed no significant difference in either diet with or without exogenous enzyme. |
