The effect of plant-based diet and suboptimal environmental conditions on digestive function and diet-induced enteropathy in rainbow trout (Oncorhynchus mykiss )

Abstract

This experiment investigated intestinal enteropathy and digestive function of rainbow trout challenged with soybean meal-based diet (SBM) at optimal or suboptimal environments created by normal or reduced water flow, respectively. Oxygen level remained above 7 mg L -1 for optimal environment and between 4 and 5 mg L -1 for suboptimal environment. Triplicate groups of fish (mean body weight 74 g) were fedfishmeal-based diet (FM) or SBM at optimal environment in period 1 (28 days). In period 2 (42 days), fish were subjected to a change from FM to SBM or remained on the same diet as used in period 1. The fish were also exposed to change from optimal to suboptimal environment or remained under optimal conditions. The fish subjected to change from FM to SBM, regardless of their environment, showed similar degree of enteropathy from day 14. Lipid and starch digestibility was lower in SBM-fed fish at suboptimal environment compared to fish fed the same diet at optimal environment.Crude protein digestibility, however, was highest in SBM-fed fish at suboptimal environment throughout period 2. In conclusion, in SBM-fed rainbow trout, exposure to suboptimal environment did not change the degree of enteropathy; however, lipid and starch digestibility were further reduced. K E Y W O R D Sapparent digestibility coefficients, digestive function, enteritis, hypoxia, rainbow trout, soybean meal | INTRODUCTIONThe use of plant ingredients in salmonid feeds to improve sustainability of aquaculture may lead to challenges including impaired digestive function, reduced growth and increased risk of developing gastrointestinal disorders such as soybean meal-induced enteritis (SBMIE). The negative effects of plant ingredients are attributed to the presence of non-starch polysaccharides (NSP) and antinutritional factors (ANF).SBM has been used as a model to study the effect of plant ingredients on gut health and function of salmonids (Krogdahl, Bakke-Mckellep, & Baeverfjord, 2003;Mosberian-Tanha et al., 2016;Romarheim et al., 2008;Urán, Aydin, Schrama, Verreth, & Rombout, 2008). The inclusion of SBM has shown to adversely affect the apparent digestibility coefficients (ADC) of nutrients and energy (Opstvedt et al., 2003;Romarheim et al., 2006). Furthermore, it has been shown that SBM can reduce activity of digestive enzymes in the distal intestine (DI)of Atlantic salmon (Salmo salar) (Chikwati et al., 2013;Krogdahl et al., 2003). The reduced activity of digestive function may partly be due to to reduce feed intake and increase mortality in juvenile lake trout (Salvelinus namayeush) (Beamish & Tandler, 1990), and under chronic exposure, it also causes gill damage and hyperplasia (Meade, 1985). In contrary, in another experiment, chronic exposure to sublethal levels of ammonia did not change feed intake in Atlantic salmon kept at 12°C (Kolarevic et al., 2013).It is not known how the combination of a suboptimal environment (such as hypoxia) and a plant-based diet (such as SBM-based diet) may affect digestive function and intestinal h...

Corn gluten meal induces enteritis and decreases intestinal immunity and antioxidant capacity in turbot (Scophthalmus maximus) at high supplementation levels

“…Fish intestine health status was determined by endogenous and exogenous materials, in which the feedstuffs had been extensively researched [ 16 ]. It has earlier been established that the plant protein supplemented in the diet impairs the intestinal health status in several carnivorous fish species, accompanied with poor nutrient digestibility [ 17 – 26 ]. Our previous work also revealed that dietary soybean meal induced intestinal enteritis and reduced the digestive and absorptive functions in turbot [ 27 , 28 ].…”

Study of novel carbohydrate sources on rainbow trout (Oncorhynchus mykiss) diets

“…However, the effect of the carbohydrate fraction on histological tissues has not been enough studied. The negative effects of plant ingredients are mainly due to the presence of non-starch polysaccharides and antinutritional factors (Mosberian-Tanha et al 2017). The inclusion of soybean meal has shown to develop histological alterations in the intestine of Atlantic salmon and rainbow trout such as a shortening of mucosal folds, a loss of the normal supranuclear vacuolation of the absorptive cells in the intestinal epithelium, a widening of the central stroma within the mucosal folding, infiltration of inflammatory cells in the lamina propria or enteritis , Refstie et al 2000, Krogdahl et al 2003.…”

“…Wolf and Wolfe (2005) reported that these alterations could be macroscopically visible as changes in liver size. Under intensive rearing of Atlantic salmon, a decrease on the water-dissolved oxygen creates a stress on fish increasing the permeability of the intestinal walls (Olsen et al 2002, Mosberian-Tanha et al 2017.…”

“…Diet is an important stress factor in fish that can affect liver and gut characteristics (Caballero et al 2004, Martínez-Llorens et al 2012, Jalili et al 2013, Baeza-Ariño et al 2014, Mosberian-Tanha et al 2017. For this reason, the use in fish feed of alternative components can contribute to animals to enhance their health and to overcome adverse situations such as oxygen depletion that is one of the main problems in aquaculture closed systems.…”

“…Also, some of them study the effect of hypoxia on liver and gut histology Rogers 1980, Harper and. However, to the best of our knowledge there is a lack of works focused on the study of both factors and their interaction (Tran-Ngoc et al 2016, Mosberian-Tanha et al 2017. For this reason, in the present work the main purpose was to evaluate the effect of different red beet and betaine concentration on liver and gut histological parameters before and after an acute hypoxia.…”