Journal: Aquaculture, vol. 210, p. 305–321–17, 2002
International Standard Numbers:
Open Access: none
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)-beta-glucan (P < 0.001) contents in both cereals. Soluble beta-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.