Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aquaculture Dietary Tridax procumbens leaves extract stimulated growth, antioxidants, immunity, and resistance of Nile tilapia, Oreochromis niloticus, to monogenean parasitic infection Ibrahim Adeshina a , Mohsen Abdel-Tawwab b, ⁎ , Zainab A. Tijjani a , Lateef O. Tiamiyu a , Abdolreza Jahanbakhshi c a Department of Aquaculture and Fisheries, University of Ilorin, Ilorin, Nigeria b Department of Fish Biology and Ecology, Central Laboratory for Aquaculture Research, Agriculture Research Center, Abbassa, Abo-Hammad, Sharqia, Egypt c Agricultural Research Education and Extension Organization, Iranian Fisheries Science Research Institute, Offshore Fisheries Research Centre, Chabahar, Iran ARTICLEINFO Keywords: Nile tilapia Growth Feed supplements Tridax procumbent Parasites Dactylogyrus vastator ABSTRACT Dactylogyrus vastator is a hermaphroditic monogenean ectoparasite that attacks fsh gills and can rapidly infect entire fsh stocks causing economic losses. Chemotherapy is still the frst choice among drugs used for the treatment of monogenean infections. However, these chemo-drugs are expensive and may have severe side efects. Hence, there is a need to fnd out alternative and eco-friendly therapeutics to control and treat these parasitic diseases in fsh. Therefore, the present study was conducted to assess the use of dietary Tridax pro- cumbens leaves extract (TPLE) as a functional feed additive to control this possible parasitic infection. Four isonitrogenous diets (300 g/kg crude protein) were prepared to contain 0.0 (control), 2, 4, or 6 g TPLE/kg diet. Nile tilapia, Oreochromis niloticus, juveniles (4.6 ± 0.06 g) were fed one of the experimental diets up to apparent satiation thrice a day for 8 weeks. After that, fsh from each treatment were exposed to D. vastator solution (40 individual/L) and closely monitored for any fsh mortality for 14 days. It is noted that dietary TPLE levels signifcantly promoted the fsh growth and feed consumption but feed conversion ratio and fsh survival were not afected. Additionally, dietary TPLE levels signifcantly enhanced villi length/width and absorption area of fsh intestine. Dietary TPLE signifcantly elevated the antioxidant and immunity responses. Also, post-challenge mortality in TPLE-fed fsh was signifcantly reduced in a directly proportional manner. The lowest fsh mortality (10.0%) was observed in fsh fed a diet containing 6 g TPLE/kg diet, while highest mortality (36.7%) was recorded in the control fsh group. The current study concluded that dietary TPLE has no harm efect on fsh welfare and stimulated fsh performance, intestinal morphometry, antioxidant, and immunity responses of Nile tilapia as well as its resistance to D. vastator infection with optimum levels of 4–6 g/kg diet. 1. Introduction Nile tilapia, Oreochromis niloticus, as one of the most promising species is produced intensively all over the world because of its high growth rate and high acceptability in the market. It was ranked in the fourth place (4.2 mt) among major fnfsh species in the world ̓ s aquaculture production in 2016, accounting for 8% of total fnfsh production (FAO, 2018). In this sense, intensifying the production is one of the most important approaches for developing tilapia culture in terms of increasing the productivity and proftability (El-Sayed, 2019). Monogeneans are ectoparasitic fatworms those exhibit a direct, single-host life cycle, and are thus able to multiply rapidly in high- density aquaculture environments (Klinger and Floyd, 2002). Fish in- fected with monogenean parasites including Dactylogyrus vastator can attack fsh gills causing sufer serious disorders including gill in- fammation, excessive mucous secretions, and accelerated respiration leading to fnal fsh death (Thilakaratne et al., 2003; Reed et al., 2009; Shamsi et al., 2009; Borji et al., 2012; Šimková et al., 2017). For ex- ample, D. vastator found on the gills of cyprinid has caused serious economic damage to aquaculture industries worldwide (Galli et al., 2005; Ogawa and Egusa, 1979). Thus, management requires adequate control and preventative antiparasitic treatments. Monogeneans infections are generally treated using many conven- tional chemotherapeutics, which are toxic to the fsh, environment, and https://doi.org/10.1016/j.aquaculture.2020.736047 Received 19 August 2020; Received in revised form 6 October 2020; Accepted 11 October 2020 ⁎ Corresponding author at: Fish Biology and Ecology Department, Central Laboratory for Aquaculture Research, Agriculture Research Center, Abbassa, Abo- Hammad, Sharqia 44662, Egypt. E-mail address: mohsentawwab@gmail.com (M. Abdel-Tawwab). Aquaculture 532 (2021) 736047 Available online 14 October 2020 0044-8486/ © 2020 Elsevier B.V. All rights reserved. T