{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,30]],"date-time":"2026-07-30T10:50:13Z","timestamp":1785408613441,"version":"3.56.0"},"reference-count":14,"publisher":"MDPI AG","issue":"7","license":[{"start":{"date-parts":[[2026,3,29]],"date-time":"2026-03-29T00:00:00Z","timestamp":1774742400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001807","name":"Funda\u00e7\u00e3o de Amparo \u00e0 Pesquisa do Estado de S\u00e3o Paulo","doi-asserted-by":"crossref","award":["2017\/14269-2"],"award-info":[{"award-number":["2017\/14269-2"]}],"id":[{"id":"10.13039\/501100001807","id-type":"DOI","asserted-by":"crossref"}]},{"award":["2017\/14269-2"],"award-info":[{"award-number":["2017\/14269-2"]}],"id":[{"id":"https:\/\/ror.org\/02ddkpn78","id-type":"ROR","asserted-by":"publisher"}]},{"name":"Coordena\u00e7\u00e3o de Aperfei\u00e7oamento de Pessoal de N\u00edvel Superior do Brasil","award":["88887672231202200"],"award-info":[{"award-number":["88887672231202200"]}]},{"award":["88887672231202200"],"award-info":[{"award-number":["88887672231202200"]}],"id":[{"id":"https:\/\/ror.org\/00x0ma614","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>Intensive recirculating aquaculture systems are vulnerable to spikes of nitrite, which oxidizes hemoglobin to methemoglobin and compromises oxygen transport. Methylene blue (MB) is a classical antidote for methemoglobinemia, yet its use in fish has been limited to injections or immersion baths that are impractical for large-scale operations. This study assessed whether MB incorporated into a medicated feed could mitigate acute nitrite intoxication in Nile tilapia. Fish received either a control diet or 0.1% MB diet. After five days on the experimental diets, fish were exposed to nitrite for 48 h. Control fish experienced five deaths, whereas no mortality or behavioral distress was observed in MB-treated fish. Hematology indicated significantly lower circulating methemoglobin concentration in the MB group, while the control fish had higher hemoglobin concentration and erythrocyte counts, consistent with compensatory erythropoiesis. Gill histology revealed preserved lamellae with only mild changes in MB-fed fish, whereas control fish displayed lamellar aneurysm, edema, capillary congestion, fusion and epithelial hyperplasia. Therefore, oral MB administration appears to ameliorate the physiological consequences of acute nitrite exposure, offering a scalable intervention for emergency management of nitrite spikes. Future work should define dose\u2013response relationships, evaluate post-exposure rescue, quantify gill lesions and assess MB residues in food fish.<\/jats:p>","DOI":"10.3390\/ani16071042","type":"journal-article","created":{"date-parts":[[2026,3,30]],"date-time":"2026-03-30T09:57:11Z","timestamp":1774864631000},"page":"1042","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Methylene Blue-Enriched Feed Mitigates Acute Nitrite Intoxication in Nile tilapia (Oreochromis niloticus)"],"prefix":"10.3390","volume":"16","author":[{"given":"Karoline M.","family":"Barbuio","sequence":"first","affiliation":[{"name":"Department of Animal Science, College of Agriculture, University of Sao Paulo, Avenida Padua Dias, 11, Piracicaba 13418\u2013900, SP, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gustavo H. G.","family":"Pinto","sequence":"additional","affiliation":[{"name":"Department of Animal Science, College of Agriculture, University of Sao Paulo, Avenida Padua Dias, 11, Piracicaba 13418\u2013900, SP, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-3520-0793","authenticated-orcid":false,"given":"Brunno S.","family":"Cerozi","sequence":"additional","affiliation":[{"name":"Department of Animal Science, College of Agriculture, University of Sao Paulo, Avenida Padua Dias, 11, Piracicaba 13418\u2013900, SP, Brazil"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,3,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1002\/aah.10149","article-title":"Acute Nitrite Exposure Induces Dysfunction and Oxidative Damage in Grass Carp Isolated Hemocytes","volume":"34","author":"Zhang","year":"2022","journal-title":"J. Aquat. Anim. Health"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"525","DOI":"10.1111\/raq.12184","article-title":"Toxic Effects of Nitrite on Freshwater Organisms: A Review","volume":"10","year":"2018","journal-title":"Rev. Aquac."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"e14081","DOI":"10.1111\/apha.14081","article-title":"Erythrocyte Metabolism","volume":"240","author":"Chatzinikolaou","year":"2024","journal-title":"Acta Physiol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"102022","DOI":"10.1016\/j.aqrep.2024.102022","article-title":"Effects of Chronic Nitrite Exposure on Hematological Parameters, Oxidative Stress and Apoptosis in Spotted Seabass (Lateolabrax maculatus) Reared at High Temperature","volume":"35","author":"Shen","year":"2024","journal-title":"Aquac. Rep."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1007\/s11270-023-06260-5","article-title":"A Critical Review on the Effect of Nitrate Pollution in Aquatic Invertebrates and Fish","volume":"234","author":"Banerjee","year":"2023","journal-title":"Water Air Soil Pollut."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"20","DOI":"10.1016\/j.aquaeng.2012.03.004","article-title":"Kinetics of Nitrogen Compounds in a Commercial Marine Recirculating Aquaculture System","volume":"50","author":"Urtiaga","year":"2012","journal-title":"Aquac. Eng."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"711","DOI":"10.1093\/toxres\/tfac050","article-title":"Methylene Blue: A Controversial Diagnostic Acid and Medication?","volume":"11","author":"Buzga","year":"2022","journal-title":"Toxicol. Res."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"943","DOI":"10.1111\/raq.12365","article-title":"Sustainable Aquaculture Requires Environmental-Friendly Treatment Strategies for Fish Diseases","volume":"12","author":"Lieke","year":"2020","journal-title":"Rev. Aquac."},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Zhang, X., Hui, Y., Fang, C., Wang, Y., Han, F., Lou, X., Fodjo, E.K., Cai, Y., and Kong, C. (2021). Determination of Methylene Blue and Its Metabolite Residues in Aquatic Products by High-Performance Liquid Chromatography\u2013Tandem Mass Spectrometry. Molecules, 26.","DOI":"10.3390\/molecules26164975"},{"key":"ref_10","unstructured":"Bortz, B.M. (1977). 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Aquac."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"734484","DOI":"10.1016\/j.aquaculture.2019.734484","article-title":"Hypoxia Tolerance in a Selectively Bred F4 Population of Blunt Snout Bream (Megalobrama amblycephala) under Hypoxic Stress","volume":"518","author":"Wu","year":"2020","journal-title":"Aquaculture"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"997","DOI":"10.1007\/s10695-019-00614-9","article-title":"Fish Response to Hypoxia Stress: Growth, Physiological, and Immunological Biomarkers","volume":"45","author":"Monier","year":"2019","journal-title":"Fish Physiol. Biochem."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/7\/1042\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,1]],"date-time":"2026-04-01T16:05:38Z","timestamp":1775059538000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/7\/1042"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,3,29]]},"references-count":14,"journal-issue":{"issue":"7","published-online":{"date-parts":[[2026,4]]}},"alternative-id":["ani16071042"],"URL":"https:\/\/doi.org\/10.3390\/ani16071042","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,3,29]]}}}