Small crumbled diet versus powdered diet in restricted feeding management of juvenile Nile tilapia

Abstract

ABSTRACT. The pellet size of the diet can affect both fish growth performance and the water quality of the rearing units. The present work assessed the effects of feeding juvenile Nile tilapia, Oreochromis niloticus (L.) a small crumbled diet (SCD; 0.8 mm) on water quality and growth performance. Fish were reared for six weeks in twenty 250-L polyethylene outdoor tanks at a density of 10 juveniles tank ). There were two feeding rates (standard and restricted) and two types of artificial fish diet (powdered and SCD). The standard feeding rates were reduced by 30% for restricted feeding. The concentrations of free CO 2 , reactive phosphorus, total ammonia nitrogen (TAN) and nitrite were higher in the full-fed tanks relative to the restricted-fed tanks. In the standard feeding rate groups, those tanks fed SCD had lower TAN and nitrite concentrations than tanks fed a powdered diet. The final body weight and specific growth rate of fish fed a restricted SCD were higher than the full-fed tanks. The higher levels of food waste in the powdered-diet tanks lead to impairment of fish growth performance.Keywords: unpelleted diet, crumble, particle size, restricted feeding, water quality, Oreochromis niloticus.Ração farelada versus ração desintegrada no manejo alimentar restritivo de juvenis de tilápia do Nilo ). Havia duas taxas alimentares (padrão e restritiva) e dois tipos de dietas artificiais (farelada e desintegrada). As taxas padronizadas de alimentação foram reduzidas em 30% no manejo restritivo. As concentrações de CO 2 livre, fósforo reativo, nitrogênio amoniacal total (NAT) e de nitrito foram maiores nos tanques com manejo alimentar regular em relação aos tanques com alimentação restritiva. Nos grupos alimentados segundo a tabela-padrão, aqueles tanques que receberam a ração desintegrada apresentaram menor concentração de NAT e nitrito que os tanques arraçoados com a dieta farelada. O peso corporal final e a taxa de crescimento específico dos peixes alimentados restritivamente com a ração desintegrada foram maiores que o observado nos tanques alimentados regularmente. O grande desperdício de ração nos tanques alimentados com ração farelada comprometeu o desempenho zootécnico dos peixes.Palavras-chave: ração farelada, ração desintegrada, tamanho de partícula, restrição alimentar, qualidade de água, Oreochromis niloticus.

Stability and phosphorus leaching of tilapia feed in water

“…Increasing production of fish in feed lot systems has raised concerns about the environmental impact that diets can cause in the aquatic environment (BuENO et al, 2016;HARdy, 2010). These diets, when in contact with the water, lose nutrients and, when not consumed, raise nutrient concentrations in the environment (SOARES-JúNIOR et al, 2007;OlIvEIRA-SEGuNdO et al, 2013). Among the nutrients lost from diets, phosphorus is the most critical, since it influences directly the eutrophication process (Martin et al, 2010;HAN et al, 2016;Wang et al, 2016).…”