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Dietary organic acids are increasingly being investigated as a potential means of improving growth and nutrient utilization in aquatic animals. A 9-week study was performed to compare equal amounts (2%) of different organic acids (sodium butyrate, acetate, propionate, or formate) on the growth, muscle proximate composition, fatty acid composition, cholesterol and lipid peroxidation, differential cell counts, plasma biochemistry, intestinal short-chain fatty acid (SCFA) level, and liver histopathology to red hybrid tilapia (Oreochromis sp.) (initial mean weight of 2.87 g). A second experiment was performed to determine their effects on lipid peroxidation and trimethylamine (TMA) when added at 1% to tilapia meat and left out for 24 h. The results of the first experiment showed no treatment effect to growth, feeding efficiencies, or muscle fatty acid composition, but all dietary organic acids significantly decreased intestinal SCFA. Dietary butyrate and propionate significantly decreased muscle lipid peroxidation compared to the control group, but the dietary formate treatment had the lowest lipid peroxidation compared to all treatments. Muscle crude protein and lipid in tilapia fed the formate diet were significantly lower and higher, respectively, and showed evidence of stress based on the differential cell counts, significantly higher plasma glucose and liver glycogen, as well as inflammatory responses in the liver. Although a potential benefit of dietary organic acids was a reduction to lipid peroxidation, this could be accomplished post-harvest by direct additions to the meat. In addition, inclusions of butyrate and propionate to tilapia meat significantly decreased TMA, which might be a more cost-effective option to improve the shelf life of tilapia products.

An 8-week study was conducted on the use of native tapioca starch (TS) or pre-gelatinized tapioca starch (PGTS), with or without the inclusion of isomaltooligosaccharides (IMO) at 0.5% on the growth, feeding efficiencies, muscle and plasma biochemical composition, intestinal short chain fatty acids (SCFA), differential cell counts, phagocytic ability/capacity, and liver glycogen content in African catfish, Clarias gariepinus. Each treatment was triplicated with each replicate consisting of 10 fish (initial weight of 6.2 ± 0.3 g). The bulk density (BD), pellet durability index (PDI), water stability (WS), water absorption index (WAI), water solubility index (WSI), and protein solubility (PS) were measured in all experimental diets. The results showed no significant (p > 0.05) growth differences among the treatments, but feed intake was significantly lowest (p < 0.05) in the PGTS diet, followed by the PGTS + IMO, while the significantly (p < 0.05) highest was in the TS treatment. Catfish fed the PG diets had significantly (p < 0.05) higher crude lipid but significantly (p < 0.05) lower crude protein and ash compared to those fed the TS diets. Both trypsin and chymotrypsin activities were significantly (p < 0.05) higher in the PG diets. The TS + IMO diet significantly increased the white blood cells and phagocytic activity compared to the TS diet. Meanwhile, fish fed the PGTS diet had significantly (p < 0.05) lower intestinal acetic and butyric acid than all others, but the inclusion of IMO in the PGTS diet mitigated a decrease of these. The PG starch diets had significantly (p < 0.05) higher PDI, WS, WAI, and PS than the TS diets. The uncompromised growth may have been due to dietary PG starch and IMO enhancing available energy to the fish. The mitigating effect of IMO on increasing intestinal SCFA when using PG diets may have implications to disease management, but requires further investigation.

The emerging literature has suggested essential oils (EOs) as new possible weapons to fight antimicrobial resistance due to their inherent antimicrobial properties. However, the potential pharmaceutical use of EOs is confronted by several limitations, including being non-specific in terms of drug targeting, possessing a high cytotoxicity as well as posing a high risk for causing skin irritation. Furthermore, some EOs have been demonstrated to adversely affect the cellular lipid profiles and permeability of the cell membrane, which may result in undesirable outcomes for the cells. Nevertheless, owing to their naturally complex compositions, EOs still hold undiscovered potential to mitigate antimicrobial resistance, as an alternative to existing antibiotics. To address the issue of overuse in antibiotics for crops which have led to the growing threat of antimicrobial resistance globally, EOs have also been proposed as potential biopesticides. Since the perceived advantages of antimicrobial attributes in EOs remain largely unexplored, this review aims to provide a discourse into its current practical usefulness in the agricultural setting. Finally, updated bioengineering techniques with emphasis of the biopesticide potential of EOs as a means to alleviate antimicrobial resistance will be included.

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