Abstract
O efeito de diferentes níveis de proteína bruta (32A, 32B, 36, 38, 44 e 50% PB; 3.500 kcal energia digestível) em reprodutores de tilápia-do-nilo foi avaliado. Após 30 semanas experimentais (set./14 a mar./15), 91,0% dos ovos de peixes alimentados com 44% PB eclodiram e produziram 16,4% de larvas viáveis a mais do que o tratamento que recebeu 32% PB. A produção de ovos e a fecundidade absoluta foram semelhantes entre os tratamentos (p>0,05). A motilidade e a velocidade médias do esperma, em linha reta e curvilínea, apresentaram valores satisfatórios no tratamento em 44% CP, ao contrário de 36% PB. Observou-se baixa rentabilidade com 32% PB; todavia, o lucro aumentou com o nível de proteínas na dieta. Respostas estatisticamente significativas não foram encontradas para o desempenho reprodutivo de fêmeas. Os resultados foram satisfatórios para a produção em escala comercial com o aumento da proteína bruta. A hipótese inicial foi demonstrada para a maioria dos parí¢metros avaliados em machos, crescimento de larvas e viabilidade econômica. Portanto, recomenda-se dieta com 44% PB para reprodutores de tilápia-do-nilo.
Highlights
In the last few years considerable progress has been made in the knowledge of the nutritional demands of Nile tilapia, there is still a need for further studies on nutrition that consider different categories of weight or age, as well as specific studies about broodfish (FURUYA et al, 2013), especially the supply of essential nutrients for the development of gonads, eggs and larvae (LUPATSCH et al, 2010), which is an immediate need since the aquaculture activity has shown rapid expansion recently
That kind of behavior was observed, so at the end of 30 weeks of experiment the values of weight gain (WG) and final length (FL), both in males and females, were minimal and without significant differences between the treatments, corroborating what had been mentioned by COWARD and BROMAGE (2000) and LUPATSCH et al (2010), who had found low values of WG in broodfish fed different levels of crude protein (CP)
The results obtained in this study presented growing number of viable larvae as the concentration of CP increased in the feed: the treatment with 50% CP produced 21.9% more larvae (226,318) than the treatment with 32% CP (32A; 185,573); the treatment with 44% CP exhibited survival rate 16.4% higher than the treatment with 32% CP (32A), these values do not show statistical differences
Summary
In the last few years considerable progress has been made in the knowledge of the nutritional demands of Nile tilapia, there is still a need for further studies on nutrition that consider different categories of weight or age, as well as specific studies about broodfish (FURUYA et al, 2013), especially the supply of essential nutrients for the development of gonads, eggs and larvae (LUPATSCH et al, 2010), which is an immediate need since the aquaculture activity has shown rapid expansion recently In this context, it is important to emphasize the relevance of providing adequate diets to Nile tilapia broodfish, a species raised all over the world and characterized by presenting parceled asynchronic spawning, with low fecundity rate, whose reproductive process received special attention in the last few years (NG and ROMANO, 2013; LUPATSCH et al, 2010; COWARD and BROMAGE, 2000). Comparatively to other nutrients, protein is the most expensive item in diet formulation for aquatic organisms (NRC, 2011), and that wide range may considerably interfere with the final cost of production
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