3. Results
At the end of the feeding trial, final weight of both species was not
affected by dietary treatments (meagre final body weight: 188.54 ±
10.61 control diet, 215.59 ± 5.44 1% BSY diet, 193.92 ± 0.44 2% BSY
diet; white seabream final body weight: 102.35 ± 3.33 control diet,
103.8 ± 4.28 1% BSY diet, 104.21 ± 2.18 2% BSY diet). Feed efficiency
in meagre averaged 0.77 ± 0.03 control diet, 0.89 ± 0.03 1% BSY diet,
0.91 ± 0.02 2% BSY diet and was significantly higher in fish fed BSY
supplemented diets. In white seabream feed efficiency was unaffected
by dietary treatments (0.39 ± 0.05 control diet, 0.39 ± 0.04 1% BSY
diet, 0.46 ± 0.02 2% BSY diet).
Amylase, lipase and protease activities (expressed as mU mg
protein−1) of the sum of assayed digestive sections (pyloric caeca and
intestine) and ratios between digestive enzymes of meagre and white
seabream fed the control diet are presented in Table 2. Comparatively
to white seabream, meagre exhibited significantly lower amylase and
lipase activities while the opposite was observed for protease activity.
Higher amylase:protease, lipase:protease and amylase:lipase ratios
were found in white seabream than in meagre.
In meagre, digestive protease and amylase activities were identical
in the pyloric caeca and intestine, while in white seabream activities
of both enzymes were higher in the pyloric caeca (Tables 3 and 4).
Inmeagre, and relatively to the control, dietary supplementationwith
2% BSY increased amylase activity in the pyloric caeca but not in the
intestine. Contrarily, dietary supplementation with 1% BSY decreased
amylase activity in the intestine but not in the other region of the digestive
tract. Also, no effects of dietary BSY supplementation were observed
in lipase activity irrespectively of the digestive tract section. Protease
activity was also unaffected by dietary supplementation with 2% BSY supplementation,
irrespectively the digestive section, but supplementation
with 1% BSY decreased intestine protease activity (Table 3).
In white seabream, and also comparatively to the control, amylase
activity increased in the pyloric caeca with both BSY supplementation
levels, but in the intestine itwas only increasedwith 2% BSY supplementation.
Lipase activity increased with 2% BSY supplementation only in
the pyloric caeca. Protease activity increased with dietary supplementation
of BSY in the pyloric caecawith the 2% BSY diet and in the intestine
with the 1% BSY diet (Table 4).
Similar profiles of protease activity, in relation to pH values, were
observed in the pyloric caeca and intestine of meagre and white
seabream (Fig. 1). In both species, differences in protease activities
over the pH range assayed were only detected in the pyloric caeca of
fish fed 2% BSY diet. Protease activities were higher at pH 10 than at
pH 7.
In meagre, proteolytic activity was however higher in the pyloric
caeca at pH 7, 8 and 9, in fish fed the 2% BSY diet, than with the 1% BSY
diet, but not with the control diet, while in white seabream proteases