Overfeeding-Induced Obesity Could Cause Potential Immuno-Physiological Disorders in Rainbow Trout (Oncorhynchus mykiss)

Abstract

Although over-nutrition from overfeeding-induced obesity is known to be highly associated with metabolic and immunological disorders in humans, little is known about overfeeding-induced obesity in fish farming. The purpose of this study was to investigate changes in immuno-physiological parameters, to better understand the potential risk of overfeeding–induced obesity in fish. Commercial feed was provided to fish in the overfed group until they refuse to eat, but fish in the control group was fed with the feed at 1% bodyweight per day. The hemato-serological, histological, and immunological changes were observed at weeks 2 and 8. Rainbow trout leukocytes were co-incubated with oxidized low-density lipoprotein (OxLDL), and the phagocytes engulfing the OxLDL and the presence of apoptotic cells were evaluated. The body weight, body mass index (BMI), and hepatosomatic index (HSI) index were significantly higher in the overfed group, and high lipid accumulation and fatty changes were also observed in their livers, indicating that the feeding regime used in this study led to overfeeding-induced obesity. Likewise, much higher numbers of and larger vacuoles were observed in overfed fish macrophages, showing unclear boundaries between the cytoplasm and extracellular space. In the overfed group, the expression of IL-10, HSP70, TLR2, and CD36 was significantly higher, and lymphocyte apoptosis was more evident, indicating that overfeeding-induced obese fish might have immunologic disorders. This was the first study to demonstrate that overfeeding-induced obesity could cause an immune-physiological imbalance in rainbow trout, making them more vulnerable to infectious diseases and various stressful conditions. This study will contribute to improvements in fish nutrition, feeding practices, fish nutrition, and disease prevention in the aquaculture industry.

Feed Restriction Modulates Growth, Gut Morphology and Gene Expression in Zebrafish

“…On the contrary, it has been observed that short term overfeeding of zebrafish with a high fat diet led to metabolic alterations, such as hyperglycemia and ectopic lipid accumulation in the liver [ 77 ]. Another study on overfeeding in rainbow trout observed the development of immunological disorders and increased susceptibility to infectious diseases [ 78 ]. In aquaculture, fish with better immunity and health would be preferred, as they would be more resistant to disease outbreaks, protecting the farmers from substantial loss.…”

Research Before Policy: Identifying Gaps in Salmonid Welfare Research That Require Further Study to Inform Evidence-Based Aquaculture Guidelines in Canada

“…In contrast, over-feeding (as a possible result of strong dominance hierarchies, incomplete training of personnel, etc. ), though less studied, may have welfare consequences such as fouling of the holding tank or net-pen and/or obesity resulting in possible immunological disorders (131).…”

Probiotics Have the Potential to Significantly Mitigate the Environmental Impact of Freshwater Fish Farms

“…Intestinal pathological problems resulting from experimental fish diets reflecting an obstacle in the replacement of fish proteins with alternative sources have frequently been reported [27,28,38,41,51]. Intestinal health is crucial for animal growth and the efficiency of animal feeds [52][53][54]. Intestinal pathological problems in farmed fish can be associated with the disruption of intestinal function and reduction in the efficiency of feed conversion [37].…”

“…Intestinal pathological problems in farmed fish can be associated with the disruption of intestinal function and reduction in the efficiency of feed conversion [37]. Subacute intestinal pathological problems, such as sub-acute intestinal inflammation [54], can affect feed digestibility [52]. Intestinal pathological issues may affect normal intestinal functions and produce a higher intestinal pathological index score; the subsequent inflammation can therefore result in higher excretion of nutrients resulting from impaired digestion [52][53][54].…”