Background Pesticide exposure is thought to be a major contributor to living organism health deterioration, as evidenced by its impact on both cultured fish species and human health. Commercial fish diets are typically deficient in selenium (Se); hence, supplementation may be necessary to meet requirements during stress. Therefore, this study was conducted to investigate the protective role of selenium yeast (SY) supplementation for 60 days against the deleterious effects of glyphosate and or malathion chronic toxicity at sublethal concentrations in Oreochromis niloticus . Methods Two hundred and ten fish were divided into seven groups (n = 30/group) as follows: G1 (negative control); G2 (2 mg L− 1 glyphosate); G3 (0.5 mg L− 1 malathion); G4 (glyphosate 1.6 mg L− 1 and malathion 0.3 mg L− 1); G5 (glyphosate 2 mg L− 1 and SY 3.3 mg kg− 1); G6 (malathion 0.5 mg L− 1 and SY 3.3 mg kg− 1); and G7 (glyphosate 1.6 mg L− 1; malathion 0.3 mg L− 1 and SY 3.3 mg kg− 1). Results Results revealed significant alteration in growth performance parameters including feed intake (FI), body weight (BW), body weight gain (BWG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). G4 has the highest documented cumulative mortalities (40%), followed by G3 (30%). Additionally, the greatest impact was documented in G4, followed by G3 and then G2 as severe anemia with significant thrombocytopenia; leukocytosis; hypoproteinemia; increased Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST), urea, and creatinine, as well as malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Considering the previously mentioned parameters, selenium yeast (Saccharomyces cerevisiae) (3.3 mg kg− 1 available selenium) mitigated the negative impact of both the agrochemicals, whether exposed singly or in combination, in addition to their antioxidative action. Conclusions In conclusion, our study found that organophosphorus agrochemicals, single or combined, had negative impacts on Oreochromis niloticus regarding growth performance, biochemical and hematological changes in the serum, as well as induced oxidative damage in liver and kidney tissues. Supplementation of SY at the rate of 3.3 mg kg− 1 diet (2.36 mg kg− 1 selenomethionine and 0.94 mg organic selenium) ameliorated the fish performance and health status adversely affected by organophosphorus agrochemical intoxication.

A field survey was conducted on five fish farms to trace glyphosate and malathion pollution with some physicochemical parameters. A precise half-life time, LC50-96h, of these agrochemicals on Oreochromis niloticus, as well as chronic exposure with organic selenium (OS) supplementation, were experimentally investigated. Oreochromis niloticus was subjected to the following: (negative control); (2 mg L−1 glyphosate); (0.5 mg L−1 malathion); (glyphosate 1.6 mg L−1 and 0.3 mg L−1 malathion); (glyphosate 2 mg L−1 and OS 0.8 g kg−1 diet); (malathion 0.5 mg L−1 and OS 0.8 g kg−1 diet) and (glyphosate 1.6 mg L−1; malathion 0.3 mg L−1 and OS 0.8 g kg−1 diet). Furthermore, data from the analyzed pond revealed a medium risk quotient (RQ) for both agrochemicals. The detected agrochemicals were related to their application, and vegetation type surrounding the farms, also their biodegradation was correlated to water pH, temperature, and salinity. Glyphosate and malathion had half-lives of 2.8 and 2.3 days and LC50-96h of 2.331 and 0.738 mg L−1, respectively. The severest nervous symptoms; increased oxidative stress markers, as well as high bacterial count in the livers and kidneys of fish challenged with Aeromonas hydrophila, were observed in the combined exposure, followed by a single exposure to malathion and then glyphosate. Organic selenium mitigated these impacts.