The use of probiotics in the cultivation of carp, tilapia and rainbow trout in Iraq

The present study is devoted to evaluating the effectiveness of the probiotic supplement Lactobacillus aci-dophilus in the diets of three economically significant fish species in Iraq: warm–water common carp (Cyprinus carpio) and Nile tilapia (Oreochromis niloticus) and cold–water rainbow trout (Oncorhynchus mykiss). During the 90-day experiment, the fish were kept in cages and received either a control diet or a diet enriched with a probiotic based on Lactobacillus acidophilus. Growth indicators, feed efficiency, body chemistry, and intestinal microbiological profile were evaluated. The results demonstrated a statistically highly reliable (P < 0.001) improvement in all production indicators in groups using probiotic feed. The specific growth rate (SGR) increased by 18.9-21.3%, and the feed conversion coefficient (FCR) decreased by 15.9-18.8%, depending on the species. There was a significant increase in protein (by 9.5-10.3%) and fat (by 15.4-17.2%) in the body of fish. According to the results of microbiological analysis, it was found that there was a sharp increase in the population of lactic acid bacteria and suppression of opportunistic microflora (more than 98%) in the intestinal lumen of fish receiving probiotics, which had a positive effect on the physiological state of the fish body. Thus, a preparation based on Lactobacillus acidophilus is a highly effective feed additive that improves growth, increases feeding efficiency and modulates the intestinal microbiota, and can be recommended for the sustainable development of fish farming in Iraq. In the context of aquaculture in Iraq, which is facing challenges in the form of high feed costs and the need to increase production sustainability, the use of this probiotic represents a practically significant and environmentally sound strategy.