Responses of dietary supplementation of probiotic effective microorganisms (EMs) in Oreochromis niloticus on growth, hematological, intestinal histopathological, and antiparasitic activities

Abstract

Effective microorganisms (EMs) were commonly used to improve water quality in aquaculture, but its use as a fish nutritional supplement has not been investigated. Thus, two experiments were conducted. The first experiment aimed to evaluate the effects of 0%, 2%, and 4% EM-supplemented diets on the growth, hematological, and histopathological parameters on Oreochromis niloticus under two feeding regimens A and B with either 2:1 meal ratio (morning-concentrated diet) or 1:2 (evening-concentrated diet), respectively. EM-fed fish exhibited significantly higher rates of weight gain, specific growth, survival, and feed conversion efficiency mainly in the morning-concentrated diet. WBC count, HGB, and HCT showed significant differential values at different feeding regimens, with the highest recorded with 2% EM diets. Histopathological parameters such as the intestinal perimeter ratio, mucosal fold length, intraepithelial lymphocyte, and goblet cells were elevated exponentially with increased EMs dose. In the second experiment, EM-supplemented diets were assessed for the antiparasitic activity in fish that was experimentally challenged with Trichodina species. Lower infection rates of 28% and 35% were recorded in EM-treated groups at 2% and 4% EM groups, respectively. We concluded that 2% was more efficient than 4% EMs, both for its beneficial health effects and in avoiding the overdosage-associated toxicity risk.