Pinus tabulaeformis Pollen as Replacement for 17-alpha-methyltestosterone in the Diet of Oreochromis niloticus Larvae for Sex Reversal and Growth

Abstract

Three experiments were conducted to investigate the use of pollen from Pinus tabulaeformis (PP), as a possible replacement for synthetic 17-alpha-methyltestosterone (MT) in Nile tilapia, Oreochromis niloticus larvae diets. In experiment 1, the attractability of a diet containing PP (640mg/kg) compared to a control diet containing no PP was assessed. Experiment 2, lasting 8 weeks, evaluated the effects of PP on growth, food conversion efficiency, survival, and sex inversion compared with that of 17a-methyltestosterone (MT). Results showed that after 60 days of feeding, 100% of Nile tilapia fed the MT diet converted to male; this was statistically similar to the percentage of fish fed the PP diets (81.0% to 89.1% male, p<0.05). Results of the growth trial showed that final weight (FW) and weight gain (WG) of fish fed diets containing 0.08 g/kg PP and 0.64 g PP/kg were significantly higher than those fed the MT diet (p<0.05). Feed intake (FI) of all experimental fish were statistically similar (p>0.05). The group fed 0.08 g PP/kg diet exhibited significantly higher SGR than the MT group. The MT group exhibited lower food conversion efficiency (i.e. higher FCR) than the control group. Fish fed diets containing 0.08 and 0.64 g PP/kg exhibited better FCR than those fed the MT diet. Survival was statistically similar for all dietary treatments (p>0.05). In experiment 3, fish larvae were fed: no PP (control diet), a medium dose (0.32 g/kg), and a high dose (0.64 g/kg) of PP for 14 days and assayed for alpha amylase and trypsin activities. Results showed that diets containing PP were significantly more attractive to the fish than the control diet (p<0.05) for the first 5 min. At the 6th min, results were statistically similar for both PP diets. In conclusion, PP could replace MT in effecting sex reversal from female to male with statistically similar results; it could also promote better growth and food conversion efficiency at the minimum dietary level of 0.08 mg PP/kg.