Abstract
The primary aim of this experiment was to evaluate the intestinal barrier permeability in vivo in rainbow trout (Oncorhynchus mykiss) fed increasing levels of soyabean meal (SBM). The relationship between SBM-induced enteritis (SBMIE) and the permeability markers was also investigated. Our results showed that the mean score of morphological parameters was significantly higher as a result of 37·5% SBM inclusion in the diet, while the scores of fish fed 25% SBM or lower were not different from those of the fish meal-fed controls (P<0·05). SBMIE was found in the distal intestine (DI) in 18% of the fish (eleven of sixty): ten in the 37·5% SBM-fed group and one in the 25% SBM-fed group. Sugar markers in plasma showed large variation among individuals probably due to variation in feed intake. We found, however, a significant linear increase in the level of plasma d-lactate with increasing SBM inclusion level (P<0·0001). Plasma concentration of endotoxin was not significantly different in groups with or without SBMIE. Some individual fish showed high values of endotoxin in blood, but the same individuals did not show any bacterial translocation. Plasma bacterial DNA was detected in 28% of the fish with SBMIE, and 8% of non-SBMIE fish (P=0·07). Plasma concentration of d-lactate was significantly higher in fish with SBMIE (P<0·0001). To conclude, SBMIE in the DI of rainbow trout was associated with an increase in bacterial translocation and plasma d-lactate concentration, suggesting that these permeability markers can be used to evaluate intestinal permeability in vivo.
Highlights
The primary aim of this experiment was to evaluate the intestinal barrier permeability in vivo in rainbow trout (Oncorhynchus mykiss) fed increasing levels of soyabean meal (SBM)
There was a significant reduction in feed intake with the inclusion of 37·5 % SBM in the diet compared with the fish meal (FM) diet (P = 0·04)
The growth of fish fed increasing levels of SBM was comparable with that of the fish fed FM, as the Specific growth rate (SGR) did not change in response to SBM inclusion
Summary
The primary aim of this experiment was to evaluate the intestinal barrier permeability in vivo in rainbow trout (Oncorhynchus mykiss) fed increasing levels of soyabean meal (SBM). SBMIE in the DI of rainbow trout was associated with an increase in bacterial translocation and plasma D-lactate concentration, suggesting that these permeability markers can be used to evaluate intestinal permeability in vivo. Increased gut permeability due to the loss of barrier function potentiates systemic absorption of pathogens and toxic molecules which has been shown to be associated with intestinal inflammation in mammals and fish[15,16]. Urinary or plasma levels of orally administered sugars such as sucrose, mannitol, rhamnose, lactulose and sucralose have been used as markers in mammalian intestinal permeability evaluations[17,18] In these studies the ratio of disaccharides to monosaccharides in samples are calculated and used to assess barrier function[18]. Lipopolysaccharides are endotoxins which partially form the outer membrane of Gram-negative bacteria and are known to be toxic to humans and animals[22,23]
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