Maria Angélica da Silva

This study assessed the effects of dietary shrimp head meal (SHM) on growth performance, metabolism, antioxidant status, and health of Nile tilapia ( Oreochromis niloticus ) fingerlings. Five isonitrogenous and isoenergetic diets were precisely formulated on a digestible nutrient basis, containing graded SHM levels (0, 5, 10, 15, and 20%), and fed for 45 days to fish (3.24 ± 0.07 g) reared in 50 L tanks (10 fish tank ⁻¹ ; four replicates diet ⁻¹ ) within a recirculating aquaculture system. Growth performance increased significantly with SHM inclusion, and quadratic regression analyses suggested an estimated inclusion level near 16% associated with maximal weight gain and feed conversion efficiency. Improved eviscerated weight and whole-body protein, together with reduced hepatosomatic and viscerosomatic indexes and lipid content, indicated a shift toward lean growth and efficient nutrient utilization. Enhanced villus height and elevated digestive enzyme activities (amylase, proteases, and lipases) confirmed superior nutrient assimilation. Antioxidant defenses were strengthened by higher catalase and glutathione activities in liver and muscle, while feed malondialdehyde content decreased with increasing SHM levels during storage. Hematological and biochemical improvements, including higher erythrocyte, leukocyte, and platelet counts, elevated serum protein fractions, and lower glucose, cholesterol, alanine aminotransferase, and aspartate aminotransferase levels, reflected enhanced metabolic regulation, immune competence, and hepatoprotection. Collectively, these results demonstrate that SHM functions not only as a sustainable protein source but also as a functional feed ingredient that enhances physiological resilience. The valorization of shrimp-processing residues through SHM inclusion supports circular bioeconomic development and sustainable intensification in aquaculture.

Zinc is an essential metal to living organisms, including corals and their symbiotic microalgae (Symbiodiniaceae). Both Zn(II) deprivation and overload are capable of leading to dysfunctional metabolism, coral bleaching, and even organism death. The present work investigated the effects of chemically defined Zn species (free Zn, ZnO nanoparticles, and the complexes Zn-histidinate and Zn-EDTA) over the growth of the dinoflagellates Symbiodinium microadriaticum, Breviolum minutum, and Effrenium voratum, and on the trypsin-like proteolytic activity of the hydrocoral Millepora alcicornis. B. minutum was the most sensitive strain to any form of added Zn. For the other strains, the complex [Zn(His)₂] better translated metal load into growth. This complex was the only tested compound that did not interfere with the trypsin-like activity of Millepora alcicornis extracts. Also, histidine was able to recover the activity of the enzyme inhibited by zinc. [Zn(His)₂] is a potential biocarrier of zinc for microalgae or coral cultivation. These findings suggest that the control of chemical speciation of an essential metal could lead to useful compounds that assist autotrophy, while not affecting heterotrophy, in the coral holobiont.

The inclusion of agro-industrial residues in fish diets represents a sustainable strategy for modern aquaculture. This study investigated the effects of incorporating yellow passion fruit (Passiflora edulis) residue into diets for Nile tilapia (Oreochromis niloticus) fingerlings reared in a recirculating aquaculture system (RAS) integrated with lettuce (Lactuca sativa) cultivation. Over a 60-day period, 12 tanks were used in a completely randomized design with four treatments: T1 (12% yellow passion fruit residue (PFR) with lettuce), T2 (12% PFR without lettuce), T3 (0% PFR with lettuce), and T4 (0% PFR without lettuce), each with three replicates and a stocking density of 25 fish per tank (3.75 ± 0.40 g; 5.84 ± 0.50 cm). The presence of lettuce significantly reduced ammonia levels, improving water quality. No significant differences in growth performance were observed among treatments. Antioxidant capacity was enhanced by the inclusion of 12% PFR, showing higher activities of catalase, superoxide dismutase and glutathione S-transferase. Despite a reduction in intestinal villi height in fish fed 12% PFR, no negative impacts on growth performance were identified. The study demonstrates that integrating lettuce into the RAS is effective for water treatment and that using up to 12% PFR in diets is a sustainable, functional, and promising approach for Nile tilapia, contributing to more efficient and environmentally responsible production systems.

Aquaculture plays a critical role in food security, with Nile tilapia (Oreochromis niloticus) being one of the most widely farmed species due to its resilience and adaptability. However, the reliance on traditional feed ingredients poses sustainability challenges. This study aimed to investigate the immunomodulatory effects of incorporating shrimp cephalothorax lipid extract (SCLE) and shrimp cephalothorax meal (SCM) in Nile tilapia diets as sustainable feed alternatives. Two experiments were conducted using diets with varying levels of SCLE (0.4%, 0.8%, 1.2%, and 1.6%) and SCM (5%, 10%, 15%, and 20%). A total of 200 healthy, uniformly sized Nile tilapia fingerlings were selected for two trials with average weights of 4.38±0.13 g and 3.24±0.07 g, respectively. Fish were distributed across 20 tanks and fed ad libitum for 45 days. Hematological parameters were analyzed, revealing that diets with SCLE significantly increased leukocyte, thrombocyte, and hematocrit levels, particularly at 1.6% inclusion. SCM inclusion also led to higher leukocyte counts, especially at 20%. These findings suggest that SCLE and SCM positively impact the innate immune system of Nile tilapia, enhancing their ability to resist pathogens. Additionally, the use of shrimp by-products in aquafeeds presents a viable strategy for reducing environmental waste and promoting more sustainable practices in aquaculture.