A.M. Bakke-McKellep

Bio: A.M. Bakke-McKellep is an academic researcher from Norwegian University of Life Sciences. The author has contributed to research in topics: Fish meal & Soybean meal. The author has an hindex of 20, co-authored 24 publications receiving 2194 citations.

Effects of graded levels of standard soybean meal on intestinal structure, mucosal enzyme activities, and pancreatic response in Atlantic salmon (Salmo salar L.)

Abstract: Duplicate tanks of c.280 g Atlantic salmon (Salmo salar L.) were fed for 60 days on diets in which fishmeal was substituted with graded levels of extracted soybean meal (SBM) comprising 0%, 10%, 15%, 20%, 25% or 35% of total protein. The effects on feed intake, growth, feed conversion, apparent digestibility and utilization of macronutrients and energy, pathohistological response of the distal intestine (DI), activities of digestive enzymes in the mid and distal intestinal mucosa, and faecal trypsin and plasma insulin concentrations were studied. A negative, dose-dependent effect of SBM was observed on nearly all performance parameters with a notable exception of feed intake. The lowest SBM inclusion level of 10% resulted in moderate pathohistological changes in the DI. Each subsequent increase in SBM level increased the number of fish displaying severe changes. In contrast to the mid-intestine (MI), all enzyme activities in the distal intestinal mucosa decreased dose-dependently with increasing SBM inclusion. Faecal trypsin increased up to an SBM inclusion level of 20% and then levelled off. Plasma insulin increased from 0% to 15% SBM inclusion and then decreased. The results suggest that caution should be exercised in the use of even low levels of extracted SBM in salmon feeds.

Effects of dietary soyabean meal, inulin and oxytetracycline on intestinal microbiota and epithelial cell stress, apoptosis and proliferation in the teleost Atlantic salmon (Salmo salar L.).

Abstract: Soyabean meal (SBM)-induced enteritis in the distal intestine of the teleost Atlantic salmon (Salmo salar L.) and other salmonids may be considered a model for diet-related mucosal disorders in other animals and man. The role of the intestinal microbiota in its pathogenesis was explored. Compared to diets containing fishmeal (FM) as the sole protein source, responses to extracted SBM or the prebiotic inulin, with or without oxytetracycline (OTC) inclusion, were studied following a 3-week feeding trial. Intestinal microbiota, organosomatic indices and histology, as well as immunohistochemical detection of proliferating cell nuclear antigen (PCNA), heat shock protein 70 (HSP70) and caspase-3-positive cells in the distal intestine, were studied. Distal intestine somatic indices (DISI) were higher in inulin and lower in SBM compared to FM-fed fish. The low DISI caused by SBM corresponded with histological changes, neither of which was affected by OTC, despite a significant decrease in adherent bacteria count. Image analysis of PCNA-stained sections showed a significant increase in the proliferative compartment length in SBM-fed fish, accompanied by apparent increases in reactivity to HSP70 and caspase-3 along the mucosal folds, indicating induction of cellular repair and apoptosis, respectively. Fish fed the SBM diet had higher total number as well as a more diverse population composition of adherent bacteria in the distal intestine. Thus SBM-induced enteritis is accompanied by induction of distal intestinal epithelial cell protective responses and changes in microbiota. Putative involvement of bacteria in the inflammatory response merits further investigation.

Changes in immune and enzyme histochemical phenotypes of cells in the intestinal mucosa of Atlantic salmon, Salmo salar L., with soybean meal‐induced enteritis

Abstract: Extracted soybean meal (SBM) in the diet for Atlantic salmon, Salmo salar L., causes an inflammatory response in the distal intestine. The morphological changes of the epithelial cells and a characterization of the inflammatory cell infiltrate of the distal intestinal mucosa were studied using a panel of enzyme and immunohistochemical markers. The salmon (average body weight 927 g) used in the study were fed either a fishmeal-based diet (control diet) or a diet in which 30% of the fishmeal protein was replaced with SBM protein (SBM diet). In salmon fed SBM, there were markedly reduced enzyme reactivities in the distal intestinal epithelial cells, both in the brush border [5′-nucleotidase (5′N), Mg2+-ATPase, alkaline phosphatase (ALP) and leucine aminopeptidase (LAP)] and in the intracellular structures [alkaline and acid phosphatase, non-specific esterase (NSE) and alanine aminopeptidase (AAP)]. There appeared to be an increased presence of cells of monocytic lineage, including macrophages, as well as neutrophilic granulocytes and immunoglobulin (Ig) M in the lamina propria of the SBM-fed fish. The mid intestine showed little response to the diet. The results suggest that toxic/antigenic component(s) of SBM affect the differentiation of the distal intestinal epithelial cells and may help explain the reduced nutrient digestibilities previously reported in salmonids fed extracted SBM.

Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.).

Abstract: Fasting and refeeding effects on gastrointestinal morphology and digestive enzyme activities of Atlantic salmon, held in tanks of seawater at 9 degrees C and 31 per thousand salinity, were addressed in two trials. Trial 1: Fish (mean body mass 1190 g) were fasted for 40 days and intestines sampled at day 0, 2, 4, 11, 19 and 40. Trial 2: Fish (1334 g), fasted for 50 days, were refed and sampled at day 0, 3 and 7. Mass, length, protein, and maltase, lactase, and leucine aminopeptidase (LAP) activities were analyzed for stomach (ST), pyloric caeca (PC), proximal (PI), mid (MI), and distal intestine (DI). PC contributed 50% of gastrointestinal mass and 75% of enzyme capacity. Fasting decreased mass and enzyme capacities by 20-50% within two days, and 40-75% after 40 days. In PC, specific brush border membrane (BBM) maltase activity decreased whereas BBM LAP increased during fasting. Upon refeeding, enzyme capacities were mostly regenerated after one week. The results suggest that refeeding should start slowly with about 25% of estimated feed requirement during the first 3 days, but may then be stepped up rapidly. Investigations of digestive processes of fed fish should only be performed when intestines are feed-filled to avoid bias due to effects of fasting.

Expanding the utilization of sustainable plant products in aquafeeds: a review

Abstract: Continued growth and intensi¢cation of aquaculture production depends upon the development of sustainable protein sources to replace ¢sh meal in aquafeeds. This document reviews various plant feedstuis, which currently are or potentially may be incorporated into aquafeeds to support the sustainable production of various ¢sh species in aquaculture. The plant feedstuis considered include oilseeds, legumes and cereal grains, which traditionally have been used as protein or energy concentrates as well as novel products developed through various processing technologies. The nutritional composition of these various feedstuis are considered along with the presence of any bioactive compounds that may positively or negatively aiect the target organism. Lipid composition of these feedstuis is not speci¢cally considered although it is recognized that incorporating lipid supplements in aquafeeds to achieve proper fatty acid pro¢les to meet the metabolic requirements of ¢sh and maximize human health bene¢ts are important aspects. Speci¢c strategies and techniques to optimize the nutritional composition of plant feedstuis and limit potentially adverse eiects of bioactive compounds are also described. Such information will provide a foundation for developing strategic research plans for increasing the use of plant feedstuis in aquaculture to reduce dependence of animal feedstuis and thereby enhance the sustainability of aquaculture.

Utilization of plant proteins in fish diets: effects of global demand and supplies of fishmeal

Abstract: Aquafeed ingredients are global commodities used in livestock, poultry and companion animal feeds. Cost and availability are ditated less by demand from the aquafeed sector than by demand from other animal feed sectors and global production of grains and oilseeds. The exceptions are fishmeal and fish oil; use patterns have shifted over the past two decades resulting in nearly exclusive use of these products in aquafeeds. Supplies of fishmeal and oil are finite, making it necessary for the aquafeed sector to seek alternative ingredients from plant sources whose global production is sufficient to supply the needs of aquafeeds for the foreseeable future. Significant progress has been made over the past decade in reducing levels of fishmeal in commercial feeds for farmed fish. Despite these advances, the quantity of fishmeal used by the aquafeed sector has increased as aquaculture production has expanded. Thus, further reduction in percentages of fishmeal in aquafeeds will be necessary. For some species of farmed fish, continued reduction in fishmeal and fish oil levels is likely; complete replacement of fishmeal has been achieved in research studies. However, complete replacement of fishmeal in feeds for marine species is more difficult and will require further research efforts to attain.

Role of gastrointestinal microbiota in fish

Abstract: The gastrointestinal (GI) tract of an animal consists of a very complex and dynamic microbial ecosystem that is very important from a nutritional, physiological and pathological point of view. A wide range of microbes derived from the surrounding aquatic environment, soil/sediment and feed are found to colonize in the GI tract of fish. Among the microbial groups, bacteria (aerobic, facultative anaerobic and obligate aneraobic forms) are the principal colonizers in the GI tract of fish, and in some fish, yeasts are also reported. The common bacterial colonizers in the GI tract of freshwater and marine fish include Vibrio, Aeromonas, Flavobacterium, Plesiomonas, Pseudomonas, Enterobacteriaceae, Micrococcus, Acinetobacter, Clostridium, Fusarium and Bacteroides, which may vary from species to species as well as environmental conditions. Besides, several unknown bacteria belonging to Mycoplasma, Arthrobacter, Brochothrix, Jeotgailbacillus, Ochrobactrum, Psychrobacter and Sejongia species in the GI tract of different fish species have now been identified successfully using culture-independent techniques. Gnotobiotic and conventional studies indicate the involvement of GI microbiota in fish nutrition, epithelial development, immunity as well as disease outbreak. This review also highlights the need for manipulating the gut microbiota with useful beneficial microbes through probiotic, prebiotic and synbiotic concepts for better fish health management.