Manejo alimentar no desempenho produtivo de juvenis de tilápia-do-Nilo Oreochromius niloticus e lambari-do-rabo-amarelo Astyanax altiparanae em baixas temperaturas.

Abstract

The water temperature is one of the most important factors in aquaculture and in conditions that are not adequate, especially at low temperatures for tropical species, fish show a decreasing of consumption and growth. In this context, food restriction can be a alternative management to improve the use of nutrients in diets and, consequently, to optimize the growth of tropical fish species in adverse conditions for their physiology and development. The objective of this study was to evaluate the effect of short-period of dietary restrictions at low temperatures on performance, average feed cost (AFC), body composition, blood parameters in juveniles of Nile tilapia and yellow-tailed lambari. The experiments were carried out in 18 tanks, nine for each species, Nile tilapia and yellow-tail lambari. Three feeding managements were tested for both species: 1- formulated diet was offered at all meals (morning and afternoon); 2 - formulated diet was offered in the morning; and 3: formulated diet was offered in the afternoon. The temperature was 21.4 ± 2.9ºC (minimum 12.0º C and maximum 28.6º C), with 20.4 ± 2.7ºC in the morning and 22.5 ± 2.4ºC in the afternoon. The total ammonia, phosphate, pH, electrical conductivity and total dissolved solids were 0.41 ± 0.13 mg/L, 0.28 ± 0.21 mg/L, 8.34 ± 0.48, 0, 15 ± 0.01 µS/cm and 0.08 ± 0.01 ppt, respectively. Oxygen was above 5 mg/L. At the end of 90 days of experiment, the dietary intake and feed conversion for tilapia and dietary intake for lambari were different between treatments. The AFC was lower in restrictive treatments. The body composition was similar between treatments for both species, with the exception of lambari, in which the humidity was higher in animals fed in the morning. Feeding in the morning provided higher values of AST and urea for tilapia and plasma protein for lambaris. Finally, we can conclude that at low temperatures there is no need to keep feeding in the morning and in the afternoon for the tilapia and lambari species, because regardless of the food management adopted, the species showed similar performance. However, the restrictive management lead to changes in the body composition of lambari and in some blood parameters for both species.