Probiotics for freshwater fish farming can be administered as single or multiple mixtures. The expected benefits of probiotics include disease prophylaxis, improved growth, and feed conversion parameters, such as the feed conversion rate (FCR) and specific growth rate (SGR). In the current work, we review the impact of probiotics on freshwater finfish aquaculture. Data were gathered from articles published during the last decade that examined the effects of probiotics on fish growth, FCR, and water quality in freshwater fishponds/tanks. While the expected benefits of probiotics are significant, the reviewed data indicate a range in the level of effects, with an average reduction in ammonia of 50.7%, SGR increase of 17.1%, and FCR decrease of 10.7%. Despite the variability in the reported benefits, probiotics appear to offer a practical solution for sustainable freshwater aquaculture. Disease prophylaxis with probiotics can reduce the need for antibiotics and maintain gut health and feed conversion. Considering that fish feed and waste are two significant parameters of the aquaculture ecological footprint, it can be argued that probiotics can contribute to reducing the environmental impact of aquaculture. In this direction, it would be beneficial if more researchers incorporated water quality parameters in future aquaculture research and protocols to minimize aquaculture’s environmental impact.

Legislation and interest exists to protect and restore freshwater and marine ecosystems from the environmental impact of aquaculture. However, aquaculture-induced eutrophication remains a major environmental concern. Water soluble phosphorus, uneaten feed, feces, and metabolic waste from farmed fish increase phosphorus concentrations in adjacent waters. In open freshwater fish farms, in particular, the effects can be more immediate, as excess phosphorus is introduced directly into ecosystems. Several intestinal enzymes, transporters, and regulating factors have been implicated in farmed fish dietary phosphorus retention. For example, alkaline phosphatase and other transporters aid in the absorption of phosphorus in the anterior intestine, while pH, calcium, and vitamin D influence these enzymes and transporters. This process may also be influenced by intestinal morphology and the gut microbiome. To reduce phosphorus pollution from open flow fish farms, a thorough understanding of the processes that affect nutrient retention and absorption, as well as the impact of dietary factors, anti-nutritional substances, and intestinal morphology, is required. Aquaculture can be made more sustainable by reducing phosphorus release. This can be achieved by optimizing feed composition, adding functional feed ingredients, managing gut health, and treating effluent aquaculture waters with bioremediation and absorbing materials. Anti-nutritional factors can be mitigated through processing and through the use of functional feed additives. Addressing these issues will reduce aquaculture’s environmental impact, ensuring aquatic ecosystem health and global food security. In addition, treating effluent aquaculture waters with bioremediation and absorbing materials can remove phosphorus from the water, preventing it from entering the environment. This can further reduce the environmental impact of aquaculture and help to ensure the sustainability of this sector.

The purpose of this study was to evaluate the dietary use of novel silage that was created by combining three agro-industrial wastes produced in bulk, i.e., olive mill wastewater, grape pomace, and deproteinized feta cheese whey, in the diets of broiler chickens. A total of 216 one-day-old male Ross-308 chicks were randomly allocated to three treatment groups with six replications (12 chicks per pen). Three isocaloric and isonitrogenous diets were formulated to include the examined silage at 0%, 5%, or 10%. Commercial breeding and management procedures were employed throughout the trial. At the end of the trial (day 35), tissue samples were collected for analysis. Feeding 10% silage resulted in increased (p ≤ 0.001) final body weight (p ≤ 0.001) and feed intake. Jejunum and cecum microflora, as well as breast and thigh meat microflora, were modified (p ≤ 0.05) by the dietary inclusion. Thigh meat oxidative stability was improved (p < 0.01) by the silage supplementation. In addition, breast and thigh meat fatty acid profiles were different, respectively, (p < 0.05) in the supplemented treatments compared to the control. The examined silage was successfully tested in broiler diets with potential benefits for their performance and meat quality.

The use of antibiotics in open-water aquaculture is often unavoidable when faced with pathogens with high mortality rates. In addition, seasonal pathogen surges have become more common and more intense over the years. Apart from the apparent cost of antibiotic treatment, it has been observed that, in aquaculture practice, the surviving fish often display measurable growth impairment. To understand the role of gut microbiota on the observed growth impairment, in this study, we follow the incidence of Photobacterium damselae subsp. piscicida in a seabass commercial open-water aquaculture setting in Galaxidi (Greece). Fish around 10 months of age were fed with feed containing oxytetracycline (120 mg/kg/day) for twelve days, followed by a twelve-day withdrawal period, and another eighteen days of treatment. The fish were sampled 19 days before the start of the first treatment and one month after the end of the second treatment cycle. Sequencing of the 16S rRNA gene was used to measure changes in the gut microbiome. Overall, the gut microbiota community, even a month after treatment, was highly dysbiotic and characterized by very low alpha diversity. High abundances of alkalophilic bacteria in the post-antibiotic-treated fish indicated a rise in pH that was coupled with a significant increase in gut parasites. This study’s results indicate that oxytetracycline (OTC) treatment causes persistent dysbiosis even one month after withdrawal and provides a more suitable environment for an increase in parasites. These findings highlight the need for interventions to restore a healthy and protective gut microbiome.

The present study investigated the effects of two feed additives, the first containing an herbal mixture of oregano, garlic, sage, and rock samphire extracts and the second containing tributyrin (glyceryl tributyrate) when fed to broiler chickens. A total of 360 one-day-old chicks were randomly allocated to four treatments (6 replicate pens of 15 chicks). One treatment served as the unsupplemented control, whereas the feeds of the other three treatments were supplemented either with the herbal additive (3 g/kg), the tributyrin additive (1 g/kg), or both additives. The duration of the trial was 37 days. Data were collected on growth performance, intestinal microbiota and morphology, and some meat quality parameters. The combined supplementation improved (p < 0.05) weigh gain, feed conversion ratio, and the European Efficiency Factor. In the cecum, the combined supplementation lowered (p < 0.05) the microbial populations of aerobes, anaerobes, Escherichia coli, total Enterobacteriaceae, and Clostridium spp. compared to the other treatments. Fecal coccidial oocyst counts were also reduced (p < 0.01) by the combined supplementation. The herbal mixture supplementation improved (p < 0.05) breast and thigh meat resistance to oxidation. In conclusion, the combined dietary supplementation with the examined feed additives could be utilized to improve the performance and intestinal health of broiler chickens.