ABSTRACT. Tilapia masculinization can be induced by oral administration of α-methyltestosterone (MT), which is commonly dissolved in ethanol to be added to the feed. However, there are many benefits in using alternative vehicles, such as oil. The incorporation time, vehicles quantity, safety for handlers, fish and the environment are favorable factors. In fry fed for 35 days under temperature control, we found that masculinization rate was similar in both incorporation vehicles of MT (oil or ethanol) in the concentrations studied (30 and 60 mg MT kg-1 feed). In an experiment, using hormone oil dissolution and oral administration at 30 mg MT kg-1 feed, it was observed that the longer the administration time, the lower the coefficient of variation in the masculinization rate. Therefore, administration for 32 days showed the lowest variability in the masculinization rate (99.8 ± 0.5 %), compared to 24 (98.5 ± 3.0 %), 16 (97.0 ± 6.0 %) and 8 (89.0 ± 8.8 %) days. The field experiment confirmed the results obtained in the lab. We concluded that the oil can be used as MT vehicle and we recommend to dispense it at the lowest hormonal concentration (30 mg MT kg-1 feed) for 32 days for tilapia masculinization. ABSTRACT αmethyltestosterone α methyltestosterone MT, , (MT) feed However time quantity handlers factors 3 control (3 6 kg1 kg 1 kg- . Therefore 99.8 998 99 (99. 05 0 5 0. %, % 2 98.5 985 98 (98. 3. 97.0 970 97 (97. 6. 89.0 890 89 (89. 88 8. lab (MT ( 99. 9 (99 98. (98 97. (97 89. (89 (9 (8

Abstract Tilapia is one of the most important aquaculture species due to the desirable characteristics as easy reproduction and quick growth in several farming systems, including the recirculating aquaculture systems RAS. In this, the high flow of water to remove waste casually stimulates the fish to swim backset, and growth performance may be improved. Increasing the speed of swimming can improve performance within certain limits, in which however if exceeded can be harmful. Fish may be exhausted leading to impaired growth or even mortality. The objective of this work was to evaluate the growth performance of tilapia juveniles under sustained swimming exercise at different speeds. Additionally, the fish stocking density effect was tested in the sustained swimming exercise condition. In the first experiment, Nile tilapia juveniles were submitted in triplicates to sustained swimming exercise in speeds of control (not exercised), 1 BL/s (body length per second), 1.5 BL/s and 2 BL/s. In the second experiment, two fish stocking densities were tested in triplicates in sustained swimming exercise in speed of 2 BL/s and control not exercised. Fish growth performance was improved by sustained swimming exercise in speeds up to 2 BL/s. No expressive fish mortalities were observed in both experiments. The comparison between the two stocking densities does not allow us to safely say tilapia can be reared at stocking densities in order of 1,000 fish/m3, even under sustained swimming exercise. Other densities need to be tested. RAS backset limits harmful mortality Additionally condition experiment exercised, exercised , exercised) BLs BL s body second, second) 15 5 1. experiments 1000 000 1,00 fishm3 fishm m3 m fish/m3 100 00 1,0 fish/m 10 0 1,

A constituição genética de cada cultivar de milho é fator preponderante para determinar o nível de dano provocado pela lagarta-do-cartucho, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae); contudo, são escassas as informações sobre o desempenho de diversas cultivares comerciais em relação ao ataque da praga. Objetivou-se, neste trabalho, identificar cultivares de milho menos danificadas pela lagarta-do-cartucho em condições de campo, visando aprimorar o manejo em áreas com histórico de altas infestações da praga e fornecer subsídios para programas de melhoramento genético. O trabalho foi realizado no período da safra de verão, anos agrícolas de 2006/2007 e 2007/2008; e da safrinha, ano agrícola 2007 nos municípios de Capão Bonito (SP), Tatuí (SP) e Coroados (SP). Em cada campo experimental foram realizados dois experimentos, sendo um para híbridos simples e triplos (HST) e outro para híbridos duplos e variedades (HDV). O delineamento experimental foi o de blocos ao acaso, com três e quatro repetições para HST e HDV respectivamente. Avaliou-se a injúria foliar provocada pela lagarta-do-cartucho após infestação natural, com base em escala de notas variando de 1 a 10. Constatou-se diferença significativa entre as cultivares em relação à injúria da lagarta-do-cartucho pelo teste F (P<0,05). Os resultados permitiram concluir que as cultivares DKB 390 (híbrido simples) e DKB 979 (híbrido triplo) são menos danificadas, constituindo germoplasma promissor quanto à resistência à lagarta-do-cartucho.

The genetics of maize cultivars is one of the factors that influence on damage level caused by fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae); however, there is no information about performance of commercial cultivars for this pest attack. The aim of the present research was to identify maize cultivars less damaged by the fall armyworm under field conditions, which could be used as an additional tool for managing the pest in areas with history of high infestations, as well as for genetic breeding programs. The experiments were accomplished during the summer season 2006/2007 and 2007/2008; and off-season 2007, in Capão Bonito (SP), Coroados (SP) e Tatuí (SP). Two experiments were set up in each area, one with simple and triple hybrids (HST) and other with double hybrids and varieties (HDV). The experimental design was in randomized blocks, with three and four replications for HST and HDV, respectively. The leaf injury caused by fall armyworm under natural infestation was evaluated using a rating scale ranging from 1 to 10. There were significant differences among cultivars for leaf injury, with the cultivars DKB 390 (simple hybrid) and DKB 979 (triple hybrid) being less damaged. These cultivars may serve as potential sources of resistance against the fall armyworm.