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The effects of crowding and heat stress on the intestinal flora, body-weight gains and feed efficiencies of rats and chicks were investigated. For the condition of crowding 25 rats were kept in a cage and 3 rats were kept in a cage for the control group. For the condition of heat stress, rats were kept at 31°C and 25°C for the control. The chicks were kept at 35°C for the heat stress and 25°C for the control. Irrespective of the types of stress and host species, aerobic bacteria, i.e., staphylococci and one or two bacterial groups of streptococci, enterobacteria and corynebacteria increased commonly in the small intestine. Sometimes anaerobes, i.e., peptococcaceae and bacteroides in rats increased under crowding condition and peptococcaceae and clostridia in chicks increased under heat stress. The changes of flora in the large intestine showed the similar tendency as in the small intestine. Body-weight gains and feed efficiencies were markedly suppressed under these stress conditions. These results showed that the changes of the intestinal flora and growth of host were affected with environmental stress.
Suzuki et al. (Sat,) studied this question.