Veterinary Research Forum

Abstract Aquaculture has a fundamental role in supporting global food security. In response to the escalating human requirement for protein, the production of aquatic species is expanding rapidly. Conversely, aquatic animals are frequently subjected to a variety of husbandry stress, including handling and high stocking densities. They trigger physiological stress responses negatively affecting biological processes, such as somatic growth, reproduction, and immune function, ultimately resulting in inferior performance and high mortality rates. Although antibiotics are still extensively employed, their persistent administration is associated with the emergence of bacterial resistance, destabilizes endogenous microbiota, and causes chemical residues accumulation within aquatic environments. Therefore, the industry has shifted towards eco-friendly therapeutic strategies. In this context, plant essential oils have emerged as promising feed additives. The EOs contain a rich array of bioactive compounds, possessing anti-bacterial, anti-oxidant, and immuno-stimulatory activities. The administration of EOs has been evaluated in a wide range of aquatic species to characterize their therapeutic potential and establish optimal inclusion levels. Research findings indicate that plant EOs represent effective substitutes for antibiotics, playing prominent roles in growth promotion, oxidative stress mitigation, and immune modulation. The present context reviews the beneficial roles of essential oils in modern aquaculture.

Abstract Use of various nanoparticles and vitamins to strengthen the immune system of fish to improve growth and biochemical indice, and to mitigate the harmful effects of free radicals through enhanced antioxidant enzyme activity has become the subject of numerous studies. In this study, fish with an average weight of 55.20 ± 7.90 g, after a two-week acclimation period, were randomly distributed into 18 polyethylene 300-L tanks, with 25 fish per tank. The experiment consisted of six treatments with three replicates: Control, vitamin (Vit) C100, nano-selenium (N-Se)0.40, Vit C100 + N-Se0.10, Vit C200 + N-Se0.20, and Vit C400 + N-Se0.40. Blood samples were collected post-treatment for analysis of antioxidant enzyme activities, biochemical and hematological indices as well as post-handling stress. Results indicated significant differences in antioxidant enzyme activities among treatments. The highest catalase activity was observed in Vit C100 and Vit C100 + N-Se0.10 groups. Glutathione peroxidase activity was significantly higher in the control and Vit C200 + N-Se0.20 groups. Malondialdehyde was the highest in Vit C100 + N-Se0.10 group. Superoxide dismutase activity peaked in Vit C200 + N-Se0.20 group. Biochemical indices showed significant differences among treatments except for high-density lipoprotein. Hemoglobin and red blood cell counts were significantly different. The Vit C100 + N-Se0.10 group showed the highest serum cortisol and glucose levels post-handling stress. Overall, dietary N-Se and Vit C supplementation improved antioxidant, biochemical, hematological indices and stress resistance in rainbow trout.

Abstract The effects of resveratrol as an anti-oxidant in improving growth and health have been shown in several experiments. This study aimed to evaluate the effects of different dietary resveratrol inclusion levels on digestive enzymes activity and serum biochemistry of rainbow trout (Oncorhynchus mykiss). Accordingly, 225 juvenile rainbow trout with an average body weight of 10.00 ± 1.50 g were stocked in nine experimental units. The study was performed as a completely randomized design including three dietary levels of resveratrol as follows: 0.00, 400 and 800 mg kg^-1 feed. During the experiment, fish were fed based on their respective body weight using standard feeding tables at three feeding times for 8 weeks. Nine fish were randomly selected from each treatment at the end of the 4^th and 8^th weeks of the experiment. Results revealed that supplementing 800 mg kg^-1 feed resveratrol significantly increased lipase activity (31.40 ± 0.32 U mg^-1 protein) compared to the control group (29.92 ± 0.52 U mg^-1 protein) at the end of week eight. Also, at the same time, it increased serum high-density lipoprotein (123.04 ± 1.57 mg dL^-1) compared to the control group (97.055 ± 1.463 mg dL^-1). In addition, dietary supplementation of 800 mg kg^-1 feed resveratrol effectively reduced serum alanine aminotransferase, alkaline phosphatase and aspartate aminotransferase activities along with glucose, cortisol and cholesterol. In conclusion, resveratrol can be used as a suitable food supplement to improve fish health by increasing digestive enzymes activities.

Abstract In this study the optimal amount of enriching Artemia franciscana with a synbiotic combination of Pediococcus acidilactici and fructooligosaccharide (FOS( was investigated. The experiment was conducted in a completely randomized design in ten treatments: multi-level probiotics P. acidilactici (1×10⁹, 1×10⁸ and 1× 10⁷ CFU per L) and multi-level enriched prebiotic FOS (1, 2 and 5) g per L of solution and control. To evaluate the enrichment of adult artemia with each treatment, sampling was performed at 2, 4 and 6 hr after initiation of enrichment. The results showed that a synbiotic containing a probiotic treatments P. acidilactici at 1 × 10⁹ and
1 × 10⁸ CFU per L had more bacteria than a synbiotic containing a probiotic treatment with 1 × 10⁷ CFU per L (p < 0.05), but did not show significant difference between levels of 1 × 10⁹ and 1 × 10⁸ CFU per L (p > 0.05). The highest number of attached bacteria (6.78 ± 0.03 log CFU g^-1) to adult artemia was shown after 6 hr of enrichment that showed significant difference with 2 hr, but did not show significant difference with 4 hr time. In conclusion, the results of this study showed that adult artemia in a short time (about 4 hr) unlike nauplii artemia can retain a large amount of probiotic (1 × 10⁸ CFU P. acidilactici per L and 5 g per L FOS prebiotic) on their own.

Abstract The aim of our study was to evaluate the effects of chitosan as immune stimulator on some hematological parameters and stress resistance in rainbow trout. Nine hundred rainbow trout (with initial body weight of 25 ± 0.1 g) were obtained from a local farm and acclimated to the laboratory conditions for one week. After that fish were randomly divided into four groups in three replicates. Each group received chitosan in diet at four concentrations as 0 (Control), 0.25, 0.5 and 1 percent chitosan, respectively. The trial was conducted for 8 weeks then feeding with chitosan stopped for 3 weeks later and during this time all fish were feed by control diet. The sampling was conducted to assay the hematological parameters of all groups every two weeks. In this study we assayed the resistance of fish against some environmental stresses immediately after changing the diet to the control. The results showed that using 0.25 percent chitosan in trout diets had a significant effect (P < 0.05) on hematological indices and stress resistance of rainbow trout in comparison the control group. Serum glucose level was higher in all treatment than control without any significance difference (P < 0.05). Based on the obtained results it concluded that the adding chitosan at 0.25 percent into the diet could enhance the hematological parameters and resistance against some environmental stresses in rainbow trout.