Compensatory Growth, Feed Utilization, Whole-Body Composition, and Hematological Changes in Starved Juvenile Nile Tilapia,Oreochromis niloticus(L.)

Abstract

Compensatory weight gain and some hematological changes in starved Nile tilapia, Oreochromis niloticus (L.), were studied. Nile tilapia (8.9±0.2 g) were distributed randomly at a rate of 20 fish per 100-L aquarium. Water temperature was about 25±1⁸C. Fish were classified into five groups and each group included three replicates. The control fish were fed throughout the experiment (13 weeks), and fish in the other four groups were subjected to food fasting for 1, 2, 3, or 4 weeks, and refed again up to the end of the experiment. Fish of fed groups were fed to satiation twice daily with dry pellets (30% crude protein). The fish growth decreased with increase of the fasting period except the fish group fasted for 1 week; however, its growth is enhanced after refeeding. Fish fasted for 2–4 weeks could not recover the lost weight after refeeding. The fish became hyperphagic after each fasting period. The duration of hyperphagia, which varied from few days (in W1) to several weeks (in W4), was dictated by the length of the fasting period. Fasting of Nile tilapia caused a cessation of body and skeletal growth and a reduction in Fulton condition factor (FQ) and liver-somatic index (LSI). FQ and LSI of fish fasted for 1–3 weeks were dramatically increased after refeeding compared to full-fed control. Hemoglobin (Hb) and red blood cells (RBCs) counts are significantly decreased with increase of the fasting period. After fish refeeding, Hb and RBCs values are returned to the normal level of full-fed control fish showing that the fish had recovered and became healthy. Fasted fish exhibited reduced plasma glucose concentration. After fish refeeding, glucose level of fish fasted for 1–3 weeks and refed are not significantly less than that of control fish. The group fasted for 4 weeks and refed up to 13 weeks has glucose levels significantly less than the other treatments. It could be recommended that fish fasting should not exceed one week, whereby fish growth could be compensated.