24 MARCH 2025 • WORLD AQUACULTURE • WWW.WAS.ORG inhibit pathogen proliferation in the intestine and promote fish growth. While evaluating the differences in the intestinal microbiota of hybrid catfish with great size disparities but from the same cohort, it was quite intriguing to observe a higher relative abundance of Lactococcus spp. using nextgeneration sequencing from the intestinal contents of fish that were overperforming in the ponds. In this study, we also isolated a bacterial species, Lactococcus lactis MA5, which presented beneficial features to be a potential native probiotic (Huang et al., 2024) for hybrid catfish. In a separate study comparing the microbiota of hybrids and channel catfish juveniles in different intestinal segments, we observed increasing bacterial community diversity along the intestinal tract, wherein the most diverse communities were found in the posterior segment. Additionally, differences between hybrids and channels were observed, including differences in abundances of Cetobacterium, a bacterial genus demonstrated to confer benefits to some fish hosts (Older et al., 2025 in press at Physiological Genomics). Several other catfish nutrition studies performed at Mississippi State within the past few years have assessed how various feed ingredients can affect the intestinal microbiota. These studies include the evaluation of feed supplements, alternative protein and lipid ingredients, and chemotherapeutics. For most studies, the catfish intestinal microbiome presented high resilience, with little to no modification in the composition, structure, and diversity of microbial communities. Although a 10-day course of the antibiotic florfenicol caused initial microbiota disruption, communities returned to homeostasis within a matter of days (Older et al., 2024). This robust intestinal microbiota may be linked to the natural biology and feeding behavior of catfish in the wild. Despite abrupt changes in nutrient sources during feeding trials, the bacterial communities appeared unaffected. But it is also important to point out the limited taxonomic resolution of the methods used, which only enable the bacterial genus to be the highest taxonomic level that can be reliably identified. Feed additives have been the most popular topic in catfish nutrition research conducted over the past 25 years, comprising 28% of the published articles (Figure 5). The use of probiotics, plantderived extracts, enzymes, insect by-products and different sources of minerals, amino acids, and vitamins were popular topics explored by scientists in the U.S., who used Ictalurus spp. as an animal model. It is of the utmost importance to better understand the nutritional strategies that we have at our disposal, such as feed additives, that can be used to intervene and reduce the frequency of disease outbreaks in catfish culture. Conclusions The U.S. catfish industry has come a long way, demonstrating resiliency and adaptability in the face of the challenges encountered over the last quarter century. Research innovations, such as hormone injections for spawning hybrids, development of vaccines, and improved aeration methods, have greatly assisted in increasing production efficiency. Still, there is always room for improvement in many areas of catfish aquaculture, including nutrition. Rising feed costs, driven by supply chain disruptions and global market volatility, have put pressure on feed millers to find affordable alternatives. Plant derived ingredients like high-protein distillers dried grains and corn fermented protein, and processed animal products have been refined and have emerged as viable and stable products to be included in catfish feed formulations. Catfish anemia remains a long-standing issue, with sporadic outbreaks causing concern across farms. While iron sulfate supplementation has been a go-to solution for iron-responsive anemia, recent findings suggest that excessive dietary iron could increase susceptibility to bacterial infections. Until the root causes of catfish anemia are fully understood, iron-fortified feeds should be used carefully as a reactive measure rather than a blanket preventative approach. The role of intestinal microbiota in catfish nutrition is another emerging area of interest. Studies indicate that dietary interventions, including probiotics and other feed additives, can positively influence gut health and improve disease resistance. Despite the resilience of the catfish intestinal microbiome, continued research into microbial interactions and their implications for fish health and growth is still needed. Looking ahead, a more holistic approach is envisioned to catfish nutrition research, by integrating not only the production performance measures, but also considering health parameters and how dietary manipulations can increase disease resistance. With advances in laboratorial technology, the development of novel ingredients, and a better understanding of how intestinal microorganisms can influence host health, the science of fish nutrition and health will continue to contribute to the productivity and sustainability of the U.S. catfish industry for years to come. FIGURE 5. Frequency of the nutrition topics surveyed from the scientific literature published for Ictalurus spp. from 2001-2025. The U.S. catfish industry has come a long way, demonstrating resiliency and adaptability in the face of the challenges encountered over the last quarter century. Research innovations, such as hormone injections for spawning hybrids, development of vaccines, and improved aeration methods, have greatly assisted in increasing production efficiency. Still, there is always room for improvement in many areas of catfish aquaculture, including nutrition.
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