Mananoligossacarídeo durante a reversão sexual de tilápia do nilo

Abstract

This present study aimed to evaluate the use of prebiotic mannanoligosaccharide (Bio-Mos®) during the sexual reversion to larvae of Nile tilapia. The study was realized in the Laboratory of Aquaculture of the Western Parana State University (Unioeste). Onethousand nd eighty larvae of Nile tilapia with three days old and initial average weight of 10.9 ± 1.2 mg were used. The larvae were distributed in 36 aquariums with 30 liters of usable volume each, in a completely randomized experimental design with six treatments and six replications. The treatments consisted of five levels, 0.2%, 0.4%, 0.6%, 0.8% and 1% for inclusion of Bio-Mos® and a control without the inclusion.The ad libitum feeding was carried out six times a day with diet formulated to obtain 38.6% of digestible protein, 3,500 kcal of digestible energy and 60 mg/kg of hormone masculine 17-α- methyltestosterone, keeping them isocaloric, isonitrogenous and isophosphoric. Aquariums were cleaned two times a day for withdrawal of surplus of feed and feces, and water renewal. The temperature was measured daily in the early morning and late afternoon. Dissolved oxygen, pH and conductivity were measured weekly. At the end of 30 days of reared period the fish were weighed and measured individually to obtain the zootechnical parameters as to final average weight, length, final biomass, survival, specific growth, condition factor and homogeneity of the lots. Ten fish from each replicate were preserved in formalin (10%) for later determination of sex ratio. The water quality parameters such as temperature, dissolved oxygen, pH and conductivity ranged from 24.76 to 26.16 °C, 5.7 to 5.85 mg/L, 7.32 to 7.65 and 87.67 to 111.33 μS/cm, respectively. The values of productive performance did not differ significantly (P>0.05). The values of final average weight, length, survival, specific growth and condition factor were 620 mg, 32.62 mm, 91.85%, 13.34%/day and 1.31, respectively. The effectiveness of sex reversal was 100% and there was not difference (P>0.05) in uniformity of lots of fish fed with different levels of inclusion of prebiotic in the ration. The average values of dry matter, ash, ether extract and crude protein from carcasses of fingerlings ranged from 22.93 to 28.45%, 11.80 to 13.61%, 23.67 to 29.97% and 60, 64 to 64.34%, respectively, but did not differ significantly (P>0.05) between the levels of prebiotic studied. The inclusion up to 1.0% Bio-Mos® did not affect the parameters of performance, sex ratio, survival, uniformity of lots and chemical composition of carcass of Nile tilapia during the sexual reversion.