Estratégias alimentares em peixes e suas respostas fisiológicas associadas ao desempenho

Abstract

Feed constitutes the majority of costs in intensive fish farming, so adopting feeding strategies that produce healthy fish with maximum growth rate and high feed efficiency is important for productive success. Therefore, this thesis addresses questions with high knowledge demand in three manuscripts. In the first study, we investigated the effects of feeding frequency on growth parameters, feed efficiency, survival, deformities, body composition, and muscle growth in Chirostoma estor in a 45-day experiment. Fish (weight: 180.57 ± 3.02 mg) were fed at frequencies of 4.8 and 12 feedings per day. At the end of the experimental period, fish fed 12 times a day exhibited the highest growth performance (P < 0.05). Feed conversion rate was affected by feeding frequency (P < 0.05). Fish survival was similar between treatments (P > 0.05), while deformities were less incident in animals fed more frequently (P < 0.05). The proximal body composition of the fish was affected by the treatments, as lipid content increased significantly with increased feeding frequency, but ash content decreased. Muscle fiber diameters differed among the treated animals (P < 0.05). Therefore, under the conditions of the experiment, a feeding frequency of twelve feedings a day promoted better performance for juveniles of C. estor and a lower percentage of deformities. The second manuscript aimed to evaluate the effect of restricted feeding and refeeding phases on the compensatory responses of growth, survival, digestive enzymes, intestinal histomorphology, proximal composition, plasma metabolites, and antioxidant activities in Colossoma macropomum. Fish (average weight: 7.12 ± 0.18 g) were fed with five feeding rates (FR = 2%, 4%, 6%, 8%, and 10% of live weight per day) for 30 days (restricted feeding phase) and then re-fed to apparent satiation for another 30 days (re-feeding phase). Growth parameters increased with increasing feeding rate (P < 0.05), while feed efficiency decreased. The reduction in feeding rate negatively affected physiological variables (P < 0.05); however, after refeeding, these variables were largely restored (P > 0.05). Our results indicate that a feeding rate of 6% per day provided the highest growth and feed efficiency, while full growth was achieved at 4% per day after refeeding. Considering the physiological responses, it can be concluded that a decrease in the feeding rate by 2% per day can trigger catabolism of endogenous reserves, which is an impeding factor for compensatory growth. The third manuscript investigated the effects of starvation on antioxidant responses using a cellular (multi-tissue) diagnostic approach in Colossoma macropomum. In conclusion, our results confirm that antioxidant responses are tissue-specific, and a 7-day fasting period induced oxidative stress in tambaqui liver and intestine.