Margareth Øverland

Modulation of splenic immune responses to bacterial lipopolysaccharide in rainbow trout (Oncorhynchus mykiss) fed lentinan, a beta-glucan from mushroom Lentinula edodes.

Immunostimulants (IS) are considered a promising approach for improving resistance to pathogens in fish aquaculture. At present, development of IS are complicated due to limited knowledge on the mechanisms of their action. To assess the use of global gene expression analysis for screening of candidate IS we applied lentinan, a beta-glucan from the mushroom Lentinula edodes, as a model. After feeding rainbow trout (Oncorhynchus mykiss) with lentinan-supplemented (L) and control (C) diets for 37 days, fish were injected with bacterial lipopolysaccharide (LPS), a classical inducer of inflammation. Gene expression was analyzed in LPS-challenged compared to saline-injected fish using a salmonid 1.8k cDNA microarray (SFA2.0 immunochip) and real-time qPCR. Spleen was selected for data analyses due to highest magnitude of responses and its key role in the fish immune system. A group of genes implicated in acute inflammatory responses was higher induced in C versus L, including IFN-related and TNF-dependent genes (galectins and receptors, signal transducers and transcription factors), genes involved in MHC class I antigen presentation and leukocyte recruitment. A similar trend was observed in metabolism of iron and xenobiotics, markers of oxidative and cellular stress. Interestingly, differences between C and L were similar to those observed between salmon with low and high resistance to infectious salmon anemia virus. Genes with equal responses to LPS in L and C were related to cell communication (cytokines, chemokines and receptors), signal transduction, activation of immune cells, apoptosis, cellular maintenance and energy metabolism. In conclusion, lentinan decreased the expression of genes involved in acute inflammatory reactions to the inflammatory agent while major parts of the immune response remained unchanged. Such effects are expected for IS, which should modify immunity by enhancing beneficial and reducing detrimental responses.

Evaluation of methane-utilising bacteria products as feed ingredients for monogastric animals

Bacterial proteins represent a potential future nutrient source for monogastric animal production because they can be grown rapidly on substrates with minimum dependence on soil, water, and climate conditions. This review summarises the current knowledge on methane-utilising bacteria as feed ingredients for animals. We present results from earlier work and recent findings concerning bacterial protein, including the production process, chemical composition, effects on nutrient digestibility, metabolism, and growth performance in several monogastric species, including pigs, broiler chickens, mink (Mustela vison), fox (Alopex lagopus), Atlantic salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss), and Atlantic halibut (Hippoglossus hippoglossus). It is concluded that bacterial meal (BM) derived from natural gas fermentation, utilising a bacteria culture containing mainly the methanotroph Methylococcus capsulatus (Bath), is a promising source of protein based on criteria such as amino acid composition, digestibility, and animal performance and health. Future research challenges include modified downstream processing to produce value-added products, and improved understanding of factors contributing to nutrient availability and animal performance.

Bacteria Grown on Natural Gas Prevent Soybean Meal-Induced Enteritis in Atlantic Salmon

Dietary inclusion of solvent extracted soybean meal (SBM) is associated with inflammation in the distal intestine of salmonid fish, commonly referred to as SBM-induced enteritis. The enteritis is linked to alcohol soluble components in SBM, but the mechanisms have not been established. Previous studies show that bacterial meal (BM) containing mainly Methylococcus capsulatus grown on natural gas is a suitable protein source for salmonids. The BM is rich in nucleotides, phospholipids, and small peptides that might be beneficial for intestinal homeostasis. In this study, a fish meal (FM)-based control diet (FM diet) and diets with 200 g/kg SBM (SBM diet), 300 g/kg BM (BM diet), and 300 g/kg BM and 200 g/kg SBM (BM-SBM diet) were fed to juvenile Atlantic salmon (Salmo salar) for 80 d. Dietary inclusion of SBM reduced growth (P = 0.007). Inclusion of BM reduced digestibility of protein (P = 0.002) and lipids (P = 0.011) and increased (P < 0.01) the relative weights (g/kg whole body) of total gut, liver, and stomach, and mid and distal intestine. Fish fed the SBM diet developed enteritis, lacked carbonic anhydrase 12 in the brush border of epithelial cells in distal intestine, and had more epithelial cells reacting for proliferating cell nuclear antigen compared with fish fed the other diets. Fish fed the same amount of SBM combined with BM showed no signs of inflammation in the distal intestine. Our results demonstrate that BM grown on natural gas can be used to prevent SBM-induced enteritis in Atlantic salmon.

Bacterial Protein Grown on Natural Gas as Feed for Pigs

Bacterial protein meal (BPM) produced by a mixture of Methylococcus capsulatus (Bath), Alcaligenes acidovorans, Bacillus brevis and Bacillus firmus grown on natural gas, was studied as a protein source for pigs. Three growth trials were conducted, one with weanling pigs (Expt 1) and two with growing-finishing pigs (Expts 2 and 3). In Expt 1, 64 appetitefed weanling pigs (10.4 kg average initial weight) were used to determine the effect of adding BPM (0 g, 40 g, 80 g and 120 g kg-1) to diets replacing traditional protein feedstuffs on growth performance. During week 0-2, adding BPM to diets increased average daily gain (ADG) (linear P < 0.03). During week 0-2 and week 0-4, the 120 g kg-1 BPM diet increased (P < 0.01) average daily feed intake compared with the control and the 50 g kg-1

Candida utilis and Chlorella vulgaris counteract intestinal inflammation in Atlantic salmon (Salmo salar L.).

Intestinal inflammation, caused by impaired intestinal homeostasis, is a serious condition in both animals and humans. The use of conventional extracted soybean meal (SBM) in diets for Atlantic salmon and several other fish species is known to induce enteropathy in the distal intestine, a condition often referred to as SBM induced enteropathy (SBMIE). In the present study, we investigated the potential of different microbial ingredients to alleviate SBMIE in Atlantic salmon, as a model of feed-induced inflammation. The dietary treatments consisted of a negative control based on fish meal (FM), a positive control based on 20% SBM, and four experimental diets combining 20% SBM with either one of the three yeasts Candida utilis (CU), Kluyveromyces marxianus (KM), Saccharomyces cerevisiae (SC) or the microalgae Chlorella vulgaris (CV). Histopathological examination of the distal intestine showed that all fish fed the SC or SBM diets developed characteristic signs of SBMIE, while those fed the FM, CV or CU diets showed a healthy intestine. Fish fed the KM diet showed intermediate signs of SBMIE. Corroborating results were obtained when measuring the relative length of PCNA positive cells in the crypts of the distal intestine. Gene set enrichment analysis revealed decreased expression of amino acid, fat and drug metabolism pathways as well as increased expression of the pathways for NOD-like receptor signalling and chemokine signalling in both the SC and SBM groups while CV and CU were similar to FM and KM was intermediate. Gene expression of antimicrobial peptides was reduced in the groups showing SBMIE. The characterisation of microbial communities using PCR-DGGE showed a relative increased abundance of Firmicutes bacteria in fish fed the SC or SBM diets. Overall, our results show that both CU and CV were highly effective to counteract SBMIE, while KM had less effect and SC had no functional effects.

Prevention of soya-induced enteritis in Atlantic salmon ( Salmo salar ) by bacteria grown on natural gas is dose dependent and related to epithelial MHC II reactivity and CD8α + intraepithelial lymphocytes

An experiment was carried out to study the preventive effect of bacterial meal (BM) produced from natural gas against plant-induced enteropathy in Atlantic salmon (Salmo salar). Salmon were fed a diet based on fish meal (FM) or seven diets with 200 g/kg solvent-extracted soyabean meal (SBM) to induce enteritis in combination with increasing levels of BM from 0 to 300 g/kg. Salmon fed a SBM-containing diet without BM developed typical SBM-induced enteritis. The enteritis gradually disappeared with increasing inclusion of BM. By morphometry, no significant (P>0.05) differences in the size of stretches stained for proliferating cell nuclear antigen were found with 150 g/kg BM compared with the FM diet. Increasing BM inclusion caused a gradual decline in the number of cluster of differentiation 8 α positive (CD8α+) intraepithelial lymphocytes, and fish fed BM at 200 g/kg or higher revealed no significant difference from the FM diet. Histological sections stained with antibody for MHC class II (MHC II) showed that fish with intestinal inflammation had more MHC II-reactive cells in the lamina propria and submucosa, but less in the epithelium and brush border, compared with fish without inflammation. There were no significant (P>0.05) differences in growth among the diets, but the highest levels of BM slightly reduced protein digestibility and increased the weight of the distal intestine. In conclusion, the prevention of SBM-induced enteritis by BM is dose dependent and related to intestinal levels of MHC II- and CD8α-reactive cells.

Feeding Jerusalem artichoke reduced skatole level and changed intestinal microbiota in the gut of entire male pigs

Different levels of dried Jerusalem artichoke were fed to entire male pigs 1 week before slaughter. The objective was to investigate the effect on skatole level in the hindgut and in adipose tissue, as well as the effect on microflora and short-chain fatty acids (SCFA) in the hindgut. Five experimental groups (n = 11) were given different dietary treatments 7 days before slaughtering: negative control (basal diet), positive control (basal diet + 9% chicory-inulin), basal diet + 4.1% Jerusalem artichoke, basal diet + 8.1% Jerusalem artichoke and basal diet + 12.2% Jerusalem artichoke. Samples from colon, rectum, faeces and adipose tissue were collected. Effect of dietary treatment on skatole, indole and androstenone levels in adipose tissue and on skatole, indole, pH, dry matter (DM), microbiota and SCFA in the hindgut was evaluated. Feeding increasing levels of Jerusalem artichoke to entire male pigs reduced skatole in digesta from colon and in faeces (linear, P < 0.01). There was also a tendency towards a decreased level of skatole in adipose tissue (linear, P = 0.06). Feeding Jerusalem artichoke decreased DM content in colon and faeces and pH in colon (linear, P < 0.01). Increasing levels of Jerusalem artichoke resulted in a reduced level of Clostridium perfringens in both colon and rectum (linear, P < 0.05) and a tendency towards decreased levels of enterobacteria in colon (linear, P = 0.05). Further, there was an increase in total amount of SCFA (linear, P < 0.05), acetic acid (linear, P < 0.05) and valerianic acid (linear, P < 0.01) in faeces. In conclusion, adding dried Jerusalem artichoke to diets for entire male pigs 1 week before slaughter resulted in a dose-dependent decrease in skatole levels in the hindgut and adipose tissue. The reduced skatole levels might be related to the decrease in C. perfringens and the increase in SCFA with subsequent reduction in pH.

Effect of bacterial protein meal grown on natural gas on growth performance and carcass traits of pigs

Abstract Bacterial protein meal (BPM), a new protein feedstuff produced by bacteria (Methylococcus capsulatus, Alcaligenes acidovorans, Bacillus brevis and Bacillus firmus) grown on natural gas, was evaluated as a protein source for pigs. Two growth trials were conducted, one with growing-finishing pigs and one with pigs from weaning until slaughter. In Exp. 1, 18 pigs fed restrictively (26.0 and 109.4 kg initial and final weight) were used to determine the effect of dietary inclusion of BPM (0, 60, or 120 g kg-1), replacing protein from soybean meal on growth performance and carcass traits. Adding 60 and 120 g kg-1 BPM to diets reduced (P < 0.01) ADG and feed efficiency during the growing period, but had no effect on growth performance during the finishing or overall periods. Both levels of BPM improved amino acid and lysine utilization (P < 0.01) compared with the control. Fat firmness tended to increase with inclusion of BPM. When using orthogonal contrast, both levels of BPM tended to increase carcass meatiness. In Exp. 2, 48 pigs (11.4 and 107.2 kg initial and final weight) were used to evaluate increasing levels of BPM (0, 50, 100, or 150 g kg –1) on growth performance and carcass traits from weaning at 34.5 days of age until slaughter. Bacterial protein meal reduced ADG (linear P < 0.03) during the period from weaning until five weeks post weaning and during the period from weaning until slaughter. Increasing levels of BPM tended to increase overall feed/gain. Also, BPM increased backfat firmness (linear P < 0.01), but reduced percent carcass lean (linear P < 0.05) and carcass meatiness (linear P < 0.01), and increased P2 backfat thickness and fat area in cutlet (linear P < 0.05). All levels of BPM improved amino acid and lysine utilization (linear P < 0.05) compared with the control. In conclusion, up to 120 g kg –1 BPM in diets for pigs from 26 kg live weight until slaughter had no adverse effect on overall growth performance or carcass lean or fat content. Up to 150 g kg –1 BPM to diets for pigs from weaning until slaughter reduced growth rates during the piglet period and increased carcass fat content due to marginal dietary lysine levels. Bacterial protein meal gave a dose dependent improvement in the utilization of total amino acids and lysine and the quality of back fat determined as fat firmness and fat color.

Dietary Butyrate Helps to Restore the Intestinal Status of a Marine Teleost (Sparus aurata) Fed Extreme Diets Low in Fish Meal and Fish Oil.

There is a constant need to find feed additives that improve health and nutrition of farmed fish and lessen the intestinal inflammation induced by plant-based ingredients. The objective of this study was to evaluate the effects of adding an organic acid salt to alleviate some of the detrimental effects of extreme plant-ingredient substitution of fish meal (FM) and fish oil (FO) in gilthead sea bream diet. Three experiments were conducted. In a first trial (T1), the best dose (0.4%) of sodium butyrate (BP-70 ®NOREL) was chosen after a short (9-weeks) feeding period. In a second longer trial (T2) (8 months), four diets were used: a control diet containing 25% FM (T2-D1) and three experimental diets containing 5% FM (T2-D2, T2-D3, T2-D4). FO was the only added oil in D1, while a blend of plant oils replaced 58% and 84% of FO in T2-D2, and T2-D3 and T2-D4, respectively. The latter was supplemented with 0.4% BP-70. In a third trial (T3), two groups of fish were fed for 12 and 38 months with D1, D3 and D4 diets of T2. The effects of dietary changes were studied using histochemical, immunohistochemical, molecular and electrophysiological tools. The extreme diet (T2-D3) modified significantly the transcriptomic profile, especially at the anterior intestine, up-regulating the expression of inflammatory markers, in coincidence with a higher presence of granulocytes and lymphocytes in the submucosa, and changing genes involved in antioxidant defences, epithelial permeability and mucus production. Trans-epithelial electrical resistance (Rt) was also decreased (T3-D3). Most of these modifications were returned to control values with the addition of BP-70. None of the experimental diets modified the staining pattern of PCNA, FABP2 or ALPI. These results further confirm the potential of this additive to improve or reverse the detrimental effects of extreme fish diet formulations.

HIGH-FAT DIETS IMPROVE THE PERFORMANCE OF GROWING-FINISHING PIGS

A growth experiment was conducted to evaluate the effect of high-fat diets (10% added fat) for growing-finishing pigs. The experiment comprised 40 growing-finishing pigs from 10 litters with an average initial weight of 23.4 kg and average final weight of 104.1 kg. The experiment consisted of a growing period from week 0 to 7 and a finishing period from week 8 to slaughter. During the growing, finishing and overall periods, the high-fat diet gave a significantly higher average daily gain (ADG) and better feed efficiency as kg feed per kg of weight gain (F/G) compared with a low-fat diet (1.5% added fat). Overall, the high-fat diet also gave higher ADG, lower total feed intake, better feed/gain and a shorter time to market of 6.3 days (P<0.01), compared with the low-fat diet. There were no significant differences between diets for P2 backfat thickness, lean percentage (GP2Q), carcass meatiness or meat area in cutlet, but the high-fat diets tended to reduce the fat area in the cutlet. Carcass quality determ...