Influence of three spice powders on the survival and histopathology of Oreochromis mossambicus before and after Streptococcus iniae infection

The aim of this study was to determine the effects of thyme, rosemary and fenugreek powders on disease resistance and histopathological changes in intestine and liver tissues of Oreochromis mossambicus before and after exposure to Streptococcus iniae. Four isonitrogenic (37% crude protein) and isolipidic (10% crude lipid) diets were formulated containing 0% (control) or 1.0% thyme (Thymus vulgaris), rosemary (Rosmarinus officinalis), or fenugreek (Trigonella foenum graecum). Fish were stocked at 20 fish (0.51±0.01 g), each, in twelve 21-L plastic tanks, fed for 60 days, and then infected with S. iniae. At the end of the challenge experiment the survival rates in the thyme, rosemary and fenugreek supplemented diets and unsupplemented control diet were 83.3%, 81.7%, 81.7% and 48.3%, respectively. The present study suggested the protective potential of thyme, rosemary and fenugreek in alleviating the intestinal and hepatic damage that can occur after infection with S. iniae. It was concluded that 1.0% thyme, rosemary or fenugreek can enhance disease resistance of O. mossambicus, suggesting that thyme, rosemary or fenugreek may be an alternative to antibiotics in controlling streptococcal disease in tilapia culture.