Bt-maize (MON810) and Non-GM Soybean Meal in Diets for Atlantic Salmon (Salmo salar L.) Juveniles – Impact on Survival, Growth Performance, Development, Digestive Function, and Transcriptional Expression of Intestinal Immune and Stress Responses

Abstract

Responses in Atlantic salmon (Salmo salar L.) juveniles (fry) fed diets containing genetically modified maize (Bt-maize, MON810) expressing Cry1Ab protein from first-feeding were investigated during a 99-day feeding trial. Four experimental diets were made; each diet contained ∼20% maize, either Bt-maize or its near-isogenic maternal line (non-GM maize). One pair was fishmeal-based while the other pair included standard (extracted) soybean meal (SBM; 16.7% inclusion level), with the intention of investigating responses to the maize varieties in healthy fish as well as in immunologically challenged fish with SBM-induced distal intestinal inflammation, respectively. Three replicate tanks of fry (0.17±0.01 g; initial mean weight ± SEM) were fed one of the four diets and samples were taken on days 15, 36, 48 and 99. Survival, growth performance, whole body composition, digestive function, morphology of intestine, liver and skeleton, and mRNA expression of some immune and stress response parameters in the distal intestine were evaluated. After 99 days of feeding, survival was enhanced and the intended SBM-induced inflammatory response in the distal intestine of the two groups of SBM-fed fish was absent, indicating that the juvenile salmon were tolerant to SBM. Mortality, growth performance and body composition were similar in fish fed the two maize varieties. The Bt-maize fed fish, however, displayed minor but significantly decreased digestive enzyme activities of leucine aminopeptidase and maltase, as well as decreased concentration of gut bile salts, but significantly increased amylase activity at some sampling points. Histomorphological, radiographic and mRNA expression evaluations did not reveal any biologically relevant effects of Bt-maize in the gastrointestinal tract, liver or skeleton. The results suggest that the Cry1Ab protein or other compositional differences in GM Bt-maize may cause minor alterations in intestinal responses in juvenile salmon, but without affecting overall survival, growth performance, development or health.

Gross anatomical and histomorphological features of the Acanthopagrus schlegelii digestive tract (Bleeker 1854) Perciformes, Sparidae

“…Food components that are not needed or cannot be absorbed are excreted from the rectum by the help of some enzymes and cells secreting the mucous in the posteriorly intestine and rectum. However, digestive tract describes morphological and functional dissimilarities in relation to the nutritional categories, body weight and sex of the fish species (Gu, Bakke, Valen, Lein, & Krogdahl, ).…”

Chronic Responses ofDaphnia magnaUnder Dietary Exposure to Leaves of a Transgenic (Event MON810) Bt–Maize Hybrid and its Conventional Near-Isoline

“…In contrast, negative nontarget effects of Bt-maize were found in certain cases, particularly for aquatic organisms, such as Trichoptera larvae fed Bt-maize leaves (Rosi-Marshall et al, 2007;Chambers et al, 2010), and Daphnia magna fed ground Bt-maize kernels (Bøhn et al, 2008(Bøhn et al, , 2010. Significant effects of MON810 maize were recently noted in salmon (Salmo salar) (Gu et al 2013(Gu et al , 2014, but were considered to be of minor biological significance because the overall development and health of the animals was not affected. Nontarget effects of other Bt-plants (Populus spp.)…”

Interactions between Bt crops and aquatic ecosystems: A review

“…In terms of fish, most studies have been done on the use of Bt crops in fish food for commercial species—namely, salmon and zebrafish—rather than fish likely to live in aquatic environments adjacent to Bt crops. Overall, consumption of Cry1Ab‐expressing maize did not have a detrimental effect on the survival, growth, and development of either species, although some stress responses were observed in salmon . These included decreased activity of certain digestive enzymes , increased activity of superoxide dismutase, and changes in white blood cell population .…”

“…Overall, consumption of Cry1Ab‐expressing maize did not have a detrimental effect on the survival, growth, and development of either species, although some stress responses were observed in salmon . These included decreased activity of certain digestive enzymes , increased activity of superoxide dismutase, and changes in white blood cell population . Conversely, zebrafish growth improved, transcription of superoxide dismutase decreased, and white blood cell populations were not affected by diet .…”