Interactive effects of cyclical fasting, refeeding, and dietary protein regimes on the growth performance, blood health, and intestinal histology of Nile tilapia (Oreochromis niloticus)

Abstract

Diet composition and frequency of feeding are significant elements affecting the feeding cost and revenue of fish farming. Hence, this study evaluated the interactive effects of cyclical fasting, refeeding, and dietary protein regimes on the growth performance, blood health, intestinal histology, and economic efficiency of Nile tilapia. Fish were allocated into eight groups with triplicate glass aquaria; four groups received 30% protein, and four were fed on a 25% protein feed. Fish fed on 30% or 25% protein daily or after one, two, or three days. After one, two, or three days of feeding with 30% or 25% protein feed, fish were starved in a cycling fasting refeeding regime for 60 days. After this trial, no significant (P > 0.05) differences were found between tilapia refed 30% protein after three days and that fed on 25% protein continuously in terms of the growth performance and feed conversion ratio. Dietary protein levels, cyclical fasting and refeeding, and their interaction were significant (P < 0.05) factors on the lipase, alpha-amylase, and protease activity. The intestine of Nile tilapia showed normal histological structures, while the liver showed normal hepatocytes in the fish groups fed on 30% or 25% dietary protein daily or after one or two days. Tilapia refed 30% protein after one, two, and three days as well as those fed 25% protein daily or after one day had similar red blood cells (RBCs), hemoglobulin (Hb), and hematocrit (HCT) levels. The interactive effects of cyclical fasting, refeeding, and dietary protein regimes were significant (P < 0.05) factors in alanine transaminase (ALT), aspartate transaminase (AST), total protein, albumin, and globulin levels. The superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) were markedly higher in tilapia-fed on dietary 25% protein after one, two, or three days than in the remaining groups. Tilapia fed on dietary 25% protein daily or after one or two days had higher malondialdehyde (MDA) levels than those refed on dietary 30% after one, two, or three days. The economic efficiency recorded the highest value in tilapia fed on 30% protein daily (30%) without significant differences (P > 0.05) with those fed 25% dietary protein daily (28.23%) or after one day (27.44%). In summary, the results stated that Nile tilapia fasted and refed after one day with 30% could show compensated growth without interrupting the feed utilization and health status. Further, cyclical fasting, refeeding, and dietary protein (25% or 30%) regimes are economically feasible strategies for tilapia production.