ABSTRACT
Lactobacillus spp. inhibit the growth of Campylobacter spp. in vitro. However, in chicken crops, in which Lactobacillus spp. predominate, such inhibition of Campylobacter has not been confirmed. In our previous study, feeding paddy rice to broiler chicks increased the residence time of the food, which might enhance the bactericidal activity of the crop. Here, the bactericidal activity against the remaining Campylobacter spp. in broiler crops was evaluated. A suspension prepared by mixing Campylobacter jejuni and titanium dioxide (TiO2) was inoculated into the pharynx of 26-day-old broiler chicks fed a paddy rice-based diet. The crop contents were sampled at 20-min intervals. The TiO2 residual ratio in the crop gradually decreased with time after inoculation, with 57% of the inoculated TiO2 remaining in the crop 60 min after inoculation. The survival fraction of C. jejuni in the crops was 11% at 40 min, only 1% at 60 min, and was undetectable at 80 min. Most of the inoculated C. jejuni died in the crop before entering the next segment. These data indicated that bacterial death occurred between 30 min and 40 min after inoculation. The average survival time of C. jejuni in the crop was calculated to be 37.1 min. Thus, C. jejuni remaining in a chicken crop for more than 40 min died.
ABSTRACT
We previously reported that a diet containing 65% paddy rice suppressed the colonization of Campylobacter jejuni in the cecum of broiler chicks, suggesting that this type of diet has positive effects on upper gastrointestinal tract function in broilers. To reveal the possible mechanisms involved in this antibacterial effect of the whole-grain paddy rice diet, we performed experiments comparing the digesta passage rate in the crop and gizzard, the development of gizzard, and the pH distribution in the gizzard between groups of chicks fed two different diets, such as ground corn and whole-grain paddy rice. During these experiments, we made the following observations: the chicks in the group fed the whole-grain paddy rice diet had more developed gizzards and significantly larger crop content than the chicks in the group fed the ground corn diet. The chicks fed the whole-grain paddy rice diet retained the digesta in the crop for much longer and had less variation in the pH values in the gizzard than those fed ground corn. On the basis of these observations, we concluded that the hardness of the rice hull in whole-grain paddy rice leads to a larger amount and longer retention of content in the crop, as well as the uniformity of the internal pH of the gizzard, by promoting gizzard activity. We speculate that the hardness of the rice hulls promoted the grinding activity of the gizzard, resulting in the long retention time of the digesta in the crop and uniformity of the internal pH of the gizzard, which may sterilize or suppress Campylobacter growth in the gastrointestinal tract of broiler chicks.
