This study investigated the effects of dietary Aloe vera on growth performance, some histological alterations in rainbow trout skin and gastrointestinal tract and disease resistance against Streptococcus agalactiae (S. agalactiae). Four treatments were designed including a control and Aloe vera incorporated in the fish feed at 0.01%, 0.1% and 1%, which were administrated for a period of six weeks. Results showed that Aloe vera at 0.1% and 1% administration resulted in improved specific growth rate (SGR) and feed conversion ratio (FCR). The Aloe vera-treated groups, improvement in proximal intestine, pyloric caeca and skin epidermis histology were also noted. The mortality rate after challenge with S. agalactiae was significantly low in fish fed 0.1% and 1% Aloe vera. The present study suggests that Aloe vera especially at 0.1% and 1% feed administration may enhance effectively the growth performance, gastrointestinal and skin morphology and resistance against S. agalactiae in rainbow trout
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