Effect of dietary macronutrient composition and buffering capacity on chyme characteristics and digestion kinetics in the gastrointestinal tract of freshwater rainbow trout (Oncorhynchus mykiss)

The aim of this study was to investigate the impact of dietary macronutrient composition and buffering capacity (BC) on chyme characteristics and digestion kinetics in freshwater rainbow trout (Oncorhynchus mykiss). Dietary macronutrient composition was altered by changing the protein-to-energy ratio (P:E) while keeping the fat-to-starch ratio constant. Dietary BC was increased by supplementation of CaCO3. The experiment lasted for 6 weeks. Fish were fed four diets having high and low P:E ratio and high and low CaCO3 level. This experiment was planned according to a 2x2x2 factorial design. The three factors were dietary P:E ratio, BC and time sampling after feeding (3 and 7 h). Chyme was collected from four gastrointestinal tract (GIT) segments (stomach, proximal, middle and distal intestine) and analysed for dry matter (DM), pH, osmolality, crude protein (CP) and mineral content. Relative water fluxes (RWF), electrolyte fluxes, kinetic of digestion and faecal digestibility (ADCs) were measured using yttrium oxide (Y2O3) as an inert marker. All chyme characteristics (including water fluxes) were not influenced by the interaction effect between dietary factors and sampling time (p > 0.05). Both dietary treatments did not affect chyme DM in the stomach. Low P:E diet increased (p < 0.001) chyme DM in all the intestinal segments. Dietary CaCO3 only affected (p < 0.05) chyme DM in the distal intestine. Low P:E diet decreased (p < 0.001) chyme pH in all GIT segments compared to the high P:E diet. Low CaCO3 diet decreased chyme pH in the proximal and middle intestine (p < 0.05) compared to the high CaCO3 diet. RWF were affected only by the dietary P:E ratio in the stomach and in the proximal intestine. Fish fed the high P:E diet had a lower water influx in the stomach and a higher water influx in the proximal intestine than fish fed the low P:E diet. Dietary P:E ratio affected electrolyte fluxes in the GIT, while no effect of CaCO3 was detected. Both dietary factors had a minimal or no effect on the kinetic of digestion in the different GIT segments, while a significant effect was present in all ADCs. Our findings suggest that dietary macronutrient composition, rather than buffering capacity, is the primary factor responsible for changes in chyme characteristics, water and ion fluxes in the GIT of freshwater rainbow trout. Furthermore, changes in dietary macronutrient composition and buffering capacity significantly affect faecal digestibility but are not reflected in digestion kinetics.publishedVersio

Assessing amino acid solubility of black soldier fly larvae meal in Atlantic salmon (Salmo salar) in vivo and in vitro

In vitro and in vivo methods were used to evaluate amino acids solubility of black soldier fly (BSF) larvae meal and two experimental diets (reference and test diets) for Atlantic salmon. The current study used in vitro method such as pH stat to compare and standardise the salmon extracted enzyme (SE), and commercial enzyme (CE) based on their hydrolytic capacity on a purified protein substrate. Further, an in vitro amino acid solubility of feed ingredients and diets were measured using the standardised enzyme volume from SE and CE. Results showed that SE and CE exhibit similar protein hydrolytic capacity upon standardisation on purified substrates. However, when using the two-stage hydrolysis (acidic and alkaline steps), significantly higher amino acid solubility was observed with CE except for glycine, and proline which were equally solubilised by both SE, and CE. No significant difference was observed between reference and test diet using the SE except for tyrosine, valine, leucine, and phenylalanine, which were significantly higher solubilised in reference diet than test diet. Whereas higher solubility of valine, isoleucine, aspartic acid, and glutamic acid was observed in test diet using CE than SE. Similarly, the solubility of valine, isoleucine, and glutamic acid were higher in BSF larvae meal when CE was used. The in vivo true protein digestibility of BSF larvae meal was 99%, and 81% for the test diet containing BSF larvae meal. The results demonstrated a positive correlation (r = 0.91; p < 0.01) between salmon and commercial enzymes but overall, no significant correlation was observed for amino acid solubility between in vivo and in vitro. However, there was a strong positive correlation for protein solubility using SE (r = 0.98) than CE (r = 0.74) with the in vivo true protein digestibility. The efficiency of SE, and CE can be compared, and standardised based on DH%, and hence correlates better with the in vivo protein digestibility but not with amino acid solubilities.publishedVersio

Zinc nutrition at first feeding imprints a programming effect on growth and hepatic lipid metabolism in juvenile rainbow trout

publishedVersio

Antioxidant and osteoinductive properties of organic selenium in microdiets for gilthead seabream (Sparus aurata) larvae

publishedVersio

Effect of feed ingredients on nutrient digestibility, waste production and physical characteristics of rainbow trout (Oncorhynchus mykiss) faeces.

This study assessed the effect of different dietary ingredients on the quantity and characteristics of faecal waste produced by rainbow trout (Oncorhynchus mykiss). Seven ingredients were tested: fish meal (FM), mussel meal (MM), poultry meal wet rendered (PM-W) or dry rendered (PM-D), insect meal (IM), single cell protein (SCP) and brewers grain protein (BGP). Eight experimental diets were formulated: a control diet (CON) being predominantly plant-based and seven test diets, which contained 70% of the CON diet and 30% of one of the test ingredients. Rainbow trout juveniles (65 g, 30 fish/tank) were fed the experimental diets at satiation for six weeks in triplicate groups. Dry matter (DM) and nutrient digestibility of diets and the test ingredients were measured. To estimate the faecal characteristics, particle size distribution (PSD) and removal efficiency of the faecal waste was determined. Nutrient digestibility of diets and ingredients differed significantly. Growth did not differ between the experimental diets, but DM digestibility was affected by the diet. Diets affected the amount of faecal waste produced, its removal efficiency (%) and the amount of non-removed faeces (g DM/kg DM feed). The highest and lowest removal efficiency was observed at FM and BGP diets, respectively. Accordingly, FM diet resulted in the lowest (37 g DM/kg DM feed), while BGP diet resulted in the highest (125 g DM/kg DM feed) amount of non-removed faeces. Additionally, it was also observed that differences in faecal removal efficiency can compensate for the variation in the quantity of faecal waste produced. Consistent with the faecal removal efficiency data, faeces PSD was also influenced by diets. FM and MM diets resulted in faeces with the lowest proportion of particles of <40 μm size, while BGP diet had the largest proportion of faecal particles of this size range. Furthermore, the effect of dietary ingredient composition was evident in the stability of faeces, with FM producing the most stable, whereas CON, BGP and SCP diets resulting in relatively unstable faecal pellets. In addition, due to differences in inclusion level of nutrients and their corresponding digestibility, the chemical composition of faeces differed between the diets. Overall, the study showed that dietary ingredient composition influences nutrient digestibility and is an important factor determining the amount of faecal waste produced, its removal efficiency, PSD, stability and composition in rainbow trout.publishedVersio

Does the processing of black soldier fly larvae meal affect the amino acid solubility in Atlantic salmon (Salmo salar)?

publishedVersio

Effects of the dietary supplementation of copper on growth, oxidative stress, fatty acid profile and skeletal development in gilthead seabream (Sparus aurata) larvae

The effect of dietary copper (Cu) levels on growth, oxidative stress, fatty acid profile and bone health of gilthead seabream larvae (Sparus aurata) was studied in 47 days-post-hatching fish fed 4 experimental diets containing 17, 18, 19 and 25 mg Cu/kg diet. After 21 days of feeding, larval growth and survival were not affected by the dietary Cu levels. However, larvae fed the non-supplemented diet (17 mg Cu/kg) showed clear symptoms of Cu deficiency, including increased lipid peroxidation and reduced bone mineralization. Increased peroxidation risk caused a reduction in essential fatty acids and n-3 PUFA (polyunsaturated fatty acids) contents in whole body lipids, whereas the poor vertebral body mineralization in seabream larvae was related to a marked increase in abdominal vertebrae anomalies. On the contrary, dietary Cu supplementation raised whole-body contents in DHA, EPA and n-3 PUFA and reduced MUFA, TBARS and the incidence of severe, cranial, branchiostegal rays and abdominal vertebral anomalies. Polynomial regression models applied to all these parameters suggested optimum dietary Cu levels to be 21.5–22.6 mg/kg in gilthead seabream larvae microdiets supplemented with CuSO4.5H2O. These levels (21.5–22.6 mg/kg) are in the range of the Cu contents in copepods (12–38 mg/kg) and on the verge of the dietary levels authorized by EU Commission in feeds for cultured fish species (25 mg Cu/kg diet).publishedVersio

Dietary zinc, selenium and water temperature during early seawater phase influences the development of vertebral deformities and cataract in adult Atlantic salmon

The impact of dietary trace minerals (TM; zinc and selenium) and water temperature during early seawater phase on the development of vertebral deformities and cataracts in adult Atlantic salmon was studied. Two experimental feeds (control and High TM) and two water temperatures (12 and 16 °C) were designed in a 2 × 2 factorial arrangement. The Zn and Se levels in the control and high TM diet corresponded to 150 or 200 mg Zn/kg and 0.5 or 0.7 mg Se/kg diet, respectively. Atlantic salmon post-smolts (mean weight, 138 g) were distributed in 12 tanks and were randomly assigned to one of the treatments in triplicate groups. The experimental regime lasted for 12 weeks and thereafter the fish were sampled or transferred to three net pens comprising all four treatments in a common garden. The fish were further grown on a common commercial feed and assessed for vertebral deformities and cataracts as adults (4 to 4.5 kg). Atlantic salmon post-smolt fed the control diet or reared at 16 °C grew more than those fed the high TM diet or reared at 12 °C at the end of the 12-week experimental feeding period. Vertebral mineral density, concentration of Zn and Se in the whole body, plasma and bile were influenced by the dietary treatments. The fast growth rates observed in the control diet and 16 °C exposed fish were associated with increased risk of vertebral deformities and cataract at adult stage. The preventive effect of the high TM diet on incidence and severity of vertebral deformities and cataracts was highly effective if the fish were reared at 12 °C during early seawater phase, but was reduced or absent if reared at 16 °C. Cataract inducing effect of high temperature at 16 °C was much stronger than the cataract mitigating effect of high TM diet at 16 °C. Overall, feeding Atlantic salmon post-smolts a high TM diet (Zn: 200 mg/kg; Se: 0.7 mg/kg diet) during early seawater phase for 12 weeks reduced the incidence of vertebral deformity and cataracts in adult fish, albeit subject to water temperature.publishedVersio

Blue mussel (Mytilus edulis) silage, a possible low trophic marine protein source for Atlantic salmon (Salmo salar L.)

publishedVersio

Growth Performance, Nutrient Digestibility, and Retention in Atlantic Salmon, Salmo salar L., Fed Diets with Fermented Sugar Kelp, Saccharina latissima

publishedVersio