Dietary neem oil and nonylphenol accelerate somatic growth by suppressing sex steroids mediated gonadal growth in reproductively active Labeo bata (Hamilton, 1822)

A 90-day feeding trial was conducted to study the effect of neem oil and or nonylphenol on gonadal and somatic growth performance in active reproductive phase of Labeo bata. Two hundred twenty-five L. bata (avge. wt., 48.47 +/- 1.09 g) adults were randomly distributed in five treatments following completely randomized design in triplicates. Five iso-nitrogenous, iso-caloric and iso-lipidic (30% CP, 367 kcal DE/100 g, 6% EE) practical diets were prepared viz., C (no supplements), T1 (0.5% neem oil), T2 (0.5% nonylphenol), T3, 1% combined dose (0.5% neem oil + 0.5% nonylphenol) and T4, 2% combined dose (1.0% neem oil + 1.0% nonylphenol). Lowest (p < 0.05) serum glucose, plasma protein and lipid profile values were observed in T4 group. The inhibition of gonadal development was maximum (p < 0.05) in T4 group as evident from gonado-somatic index and reduced level of plasma sex steroids associated with gonadal growth. Highest (p < 0.05) somatic growth in terms of weight gain (%), SGR and PER in T4 groups and lowest in the control group. Highest (p < 0.05) AST, ALT and lowest (p < 0.05) SOD, catalase enzyme activities were recorded in T4 group. The findings suggest dietary neem oil and nonylphenol supplementation at 2% level (1:1) can inhibit gonadal development concomitant with increased somatic growth in reproductively active L. bata. This strategy may be helpful to enhance growth of L. bata during growout phases, where significant amount of energy is diverted for reproductive organ development at the cost of somatic growth.