Trond Storebakken

Availability of protein, phosphorus and other elements in fish meal, soy-protein concentrate and phytase-treated soy-protein-concentrate-based diets to Atlantic salmon, Salmo salar

Abstract An experiment with 0.1-kg Atlantic salmon in saltwater was conducted to evaluate soy-protein concentrate as a source of dietary protein and to determine if phytase treatment of soy concentrate affected the availability of protein and essential elements. Three diets were fed to triplicate groups of fish for 84 days: Diet 1 with 61% fish meal, Diet 2 with 50% soy concentrate and 16% fish meal, and Diet 3 with 50% phytase-treated soy concentrate. The soy concentrate contained 18 g phytic acid kg −1 , and no phytate remained after phytase treatment. Soy concentrate was equivalent to fish meal as a source of dietary protein for Atlantic salmon, and incubation with phytase resulted in improved protein digestibility, feed conversion, protein retention, and reduced metabolic N-excretion. Whole-body Ca, Mg, and Zn levels, apparent digestibility coefficients of the same elements, and retentions of P and Zn were lower in fish fed the untreated soy concentrate compared to the phytase treated soy. Whole-body concentrations of Ca, Sr and Zn were correlated to P independent of dietary treatment, but the ratios between P and the other elements were not constant. The faecal output of Na was high for both soy concentrate diets independent of phytase treatment.

Estimation of gastrointestinal evacuation rate in Atlantic salmon (Salmo salar) using inert markers and collection of faeces by sieving: evacuation of diets with fish meal, soybean meal or bacterial meal

Abstract Gastrointestinal evacuation of Atlantic salmon was estimated using yttrium and ytterbium oxides (Y2O3 and Yb2O3) and collection of faeces from the outlet water of the tanks by sieving. The fish were fed three diets with different protein sources: fish meal (FM) (55% FM); soybean meal (SBM) (35% FM and 31% SBM); and bacterial meal (BM) (34% FM and 20% BM). The fish size was 0.15–0.20 kg and the water temperature was 9°C. Rate of passage was estimated by first feeding the fish the diets labelled with the inert marker Y2O3 and then changing to the same diets labelled with Yb2O3. Faeces were obtained by sieving of the outlet water and were pooled by tank every 3 h for 81 h after the switch in diets. The evacuation of the diets was expressed as the percent-wise ratio between Yb2O3 and the sum of inert markers (Y2O3+Yb2O3) in the faeces. For all three diets, ytterbium (Yb2O3) was first quantifiable in the faeces 12–15 h after the change of marker, and the gastrointestinal evacuation was almost complete 30 h after the switch, when yttrium (Y2O3) still accounted for up to 2% of the marker. The estimated rates of passage were described by s-shaped curves (R2≥0.98). The estimated time for Yb2O3 to reach 50% of the maximum marker concentration was approximately 18 h after the marker change in the fish fed the diets with FM and BM, while the corresponding value was approximately 20 h for the SBM diet. This was attributed to a slower onset of evacuation for the diet with SBM. The combination of two inert dietary markers and continuous collection of faeces permitted accurate estimation of gastrointestinal evacuation in salmon during feeding, without disturbing or stressing the fish.

Apparent digestibility of protein, amino acids and energy in rainbow trout (Oncorhynchus mykiss) fed a fish meal based diet extruded at different temperatures

A fish meal/wheat flour based dry ingredient mix was extruded at three different temperatures (100, 125 and 150 °C), by varying extrusion conditions according to two different methods. Employing method 1, the temperature of the conditioner, torque, screw speed, pressure, feed rate and process water of the extruder were varied. Whereas in method 2, conditioner temperature and screw speed were kept constant, and the variation in process water input was restricted. The diets, which contained yttrium oxide as an inert maker, were fed to three replicate groups of rainbow trout. Feces for digestibility determination were obtained by stripping. The results showed that the differences in extrusion temperature caused no significant differences in apparent digestibilities of crude protein, individual amino acids or energy. The apparent digestibility of cysteine was significantly higher for diets produced by method 1 than by method 2.

Lactic acid fermentation of wheat and barley whole meal flours improves digestibility of nutrients and energy in Atlantic salmon (Salmo salar L.) diets

The effects of lactic acid fermentation of wheat and barley whole meal flours (WMF) on digestibility parameters in Atlantic salmon were studied. The WMFs were inoculated with a specific Lactobacillus strain and fermented for 16 h at 30 °C prior to mixing with other feed ingredients and processing by extrusion. Fermentation of the WMFs significantly decreased total starch (P<0.01) and total mixed-linked (1–3)(1–4)-β-glucan (P<0.001) contents in both cereals. Soluble β-glucans decreased (P<0.001) from 25.2 to 12.0 g kg−1 dry matter in barley WMF during fermentation. In Experiment 1, where diets with 24% untreated wheat or barley WMF and 12%, 24%, or 36% fermented WMFs were fed to Atlantic salmon (0.5 kg) for 25 days, there were indications of improved starch and fat digestibility by fermentation. Experiment 2 comprised diets containing 24% untreated or fermented wheat or barley WMFs fed to each of triplicate groups of Atlantic salmon (0.5 kg) during a 17-day experimental period. This experiment showed that protein (P<0.001), fat (P<0.05) and energy (P<0.001) were more efficiently digested in diets with wheat than in diets with barley. Apparent digestibility of starch was greatly improved by fermentation (P<0.001), more in barley diets (from 47.5% to 67.0%) than in wheat diets (from 51.7% to 65.4%). Improvements in digestibility of fat (P<0.05) and energy (P<0.001) were obtained by fermenting the cereals. The absorption of Na was higher for salmon fed wheat than barley diets (P<0.05). Fermentation resulted in improved Na absorption (P<0.01); from 68.8% to 73.2% for wheat diets and from 60.3% to 71.7% for barley diets. Fermentation caused a significant (P<0.05) improvement in Zn absorption from 32.7% to 40.5% for wheat diets and from 33.2% to 43.5% for barley diets. This may be related to the significant reduction in phytic acid levels seen in both fermented cereals (P<0.001). In conclusion, the potential of wheat and especially barley as ingredients in salmon diets is greatly improved by fermentation.

Digestibility of protein, amino acids and starch in mink (Mustela vison) fed diets processed by different extrusion conditions

An experiment was carried out to evaluate the effect of different extrusion processes on digestibility of a fish-meal-based diet fed to mink. The feed was processed in a twin-screw extruder with the exit temperatures of the meal of 100, 125 or 150°C. Feed production was carried out three times, using different extrusion conditions to achieve the target temperatures. An untreated meal mixture was included as a control diet. True digestibilities of crude protein and total amino acids were lower for diets extruded at 125 and 150°C than for the control (P 0.05). The highest reduction was seen for cysteine (6.8 percentage units). Starch digestibility was increased by extrusio...

Bacterial protein meal produced on natural gas replacing soybean meal or fish meal in broiler chicken diets

Abstract The effects of replacing soybean meal or fish meal with 2, 4 or 6% bacterial protein meal (BPM) on growth performance, ileal digestibility of amino acids and sensory quality of meat, were examined using 630 broiler chickens. Weight gain from 7 – 32 days of age did not differ significantly among the treatments. Efficiency of feed conversion was increased when BPM replaced soybean meal, and abdominal fat deposition tended to decline. Feed conversion was not affected when BPM replaced fish meal. Amino acid digestibility was unaffected or improved when BPM replaced soybean meal, whereas replacement of fishmeal with BPM resulted in similar digestibility. Sensory quality of fresh thigh meat was similar among treatments, but for freeze-stored chest meat replacement of fish meal with BPM reduced off-odour and off-flavour and increased juiciness. It was concluded that 6% BPM can replace soybean meal or fish meal protein in broiler chicken diets.