Effects of dietary inclusion of the beta-adrenergic agonist, salbutamol, on growth performance and whole-body composition of rohu Labeo rohita (Hamilton) fingerlings fed diets containing two protein levels
Aquaculture
Research, 32(9): 739-747
Abstract:
A 60-day feeding experiment was conducted in the
laboratory to evaluate the effect of oral administration of the
beta-adrenergic agonist (BAA), salbutamol, on growth, nutrient utilization
and whole-body composition of rohu Labeo rohita (Hamilton)
fingerlings (average weight 5.51 ± 0.07 g) acting as a
repartitioning agent in intermediary metabolism and redistributing nutrients
for muscle synthesis. Two diets (diets 30/0 and 40/0) were formulated
containing 30% and 40% crude protein to serve as basal diets containing the
same ingredient composition. Another four diets (diets 30/3, 30/6, 40/3 and
40/6) were prepared in the same way to contain either 3 or 6 mg kg-1
BAA salbutamol at each protein level making the total of six experimental
diets. Rohu fingerlings were fed with the experimental diets in three
replicate treatments at a restricted feeding regime equivalent to 2% of body
weight (BW) day-1. A significant (P < 0.05)
interaction effect was found between dietary protein level and BAA
treatment. Dietary incorporation of BAA at both protein levels significantly
(P < 0.05) increased growth and nutrient utilization in
terms of weight gain (%), specific growth rate (SGR), feed:gain ratio (FGR)
and protein efficiency ratio (PER). BAA treatment at the 6 mg kg-1
concentration led to a 12% rise in growth with the 30% protein diet and a 6%
rise with the 40% protein diet, above their respective controls (without BAA
treatment). However, no significant differences were found by raising the
BAA concentration from 3 to 6 mg kg-1. The apparent
digestibility values for protein, lipid and energy were only higher with the
30% protein diets containing BAA. At both protein levels tested, BAA exerted
a significant (P < 0.05) positive influence on protein
retention and a negative influence on lipid retention efficiency, although
the differences between the 3 and 6 mg kg-1 BAA diets
were not significant. This indicated that BAA acted as a repartitioning
agent in suppressing lipid deposition in favour of protein accretion. BAA
induced significantly (P < 0.05) higher whole-body
protein and lipid relative to the untreated groups. The condition factor
improved significantly (P < 0.05) in the BAA-treated
dietary groups. The fillet percentage displayed a direct correlation and the
frame percentage a negative correlation with BAA concentration in the diets.
The results indicate that the BAA, salbutamol, was effective in producing
growth enhancement, improved body composition (higher protein and lower
lipid accretion) and efficient nutrient utilization at the 3 mg kg-1
dietary incorporation level and thus has a potential for application in
formulated diets for the Indian major carp, rohu, under culture conditions.
(Fisheries Laboratory, Department of Zoology,
Visva-Bharati University, Santiniketan 731 235, West Bengal, India)