The Role of Zinc Microelement in Aquaculture: a Review

LC3B-regulated autophagy mitigates zinc oxide nanoparticle-induced epithelial cell dysfunction and acute lung injury

Zinc oxide nanoparticles (ZnONPs) are widely utilized across various industries, raising concerns about their potential toxicity, especially in the respiratory system. This study explores the role of autophagy, regulated by microtubule-associated protein 1A/1B-light chain 3B (LC3B), in ZnONPs-induced toxicity using both in vivo (LC3B knockout mice) and in vitro (BEAS-2B cells) models. Our findings demonstrate that LC3B-regulated autophagy mitigates ZnONPs-induced epithelial cell dysfunction and acute lung injury. In the absence of LC3B, oxidative stress, inflammation, and intracellular zinc accumulation are exacerbated, resulting in mitochondrial dysfunction and epithelial cell death. In vitro, LC3B knockdown disrupted zinc ion transporter expression and impaired mitophagic flux in BEAS-2B cells. Treatment with zinc ion chelators alleviated these toxic effects, confirming that free zinc ions play a critical role in driving ZnONPs toxicity. These findings highlight that targeting autophagy and maintaining zinc homeostasis could offer therapeutic strategies to reduce ZnONPs-induced lung damage.

Bioaccumulation of trace metals by the gastropod Phorcus lineatus (Da Costa, 1778) from the Atlantic coast of El Jadida, Morocco

Heavy metals in coastal ecosystems represent an issue for human and environmental health worldwide. The objective of this study was to assess the state of health of Morocco's Atlantic coastline in the El Jadida region. The study was based on metal bioaccumulation in Phorcus lineatus, a species common to Atlantic coasts. Two polluted sites were selected: Haouzia (H) and Jorf-Lasfar (J). Animals were sampled monthly for determination of trace metals in the soft tissues of P. lineatus. Except for Cr, the results show a significant variation in bioaccumulation. The highest concentrations (μg g-1 dry weight) were found in individuals from J, with 10.68 ± 2.43 Cd, 107.36 ± 21.15 Zn, 666.55 ± 143.34 Fe and 184.47 ± 49.80 Cu. The maximum Metal Pollution Index value was 37.06 at site H in spring and 65.96 at site J in autumn. The J site appears significantly more polluted than H site.

Dietary zinc supplements: beneficial health effects and application in food, medicine and animals

Zinc, a crucial trace element is vital for the growth and development of humans. It is frequently described as 'the flower of life' and 'the source of intelligence'. Zinc supplements play a pivotal role in addressing zinc deficiency by serving as a vital source of this essential micronutrients, effectively replenishing depleted zinc levels in the body. In this paper, we first described the biological behavior of zinc in the human body and briefly described the physiological phenomena associated with zinc levels. The benefits and drawbacks of various zinc supplement forms are then discussed, with emphasis on the most recent zinc supplement formulations. Finally, the application of zinc supplements in food, medicine, and animal husbandry is further summarized. © 2024 Society of Chemical Industry.

Growth increase and gonadal dysfunction of the lined seahorse triggered by zinc exposure

Seahorses are characterized by unique characteristics such as a male pregnancy reproductive strategy and grasping preferences, which make these species vulnerable to various environmental risks. Zinc (Zn) is one of the most frequently occurring toxic elements in coastal waters; however, little is known about the effect of Zn exposure on seahorses. In the present study, line seahorses (Hippocampus erectus) were exposed to waterborne Zn (0.2 and 1.0 mg/L) and the impact on growth and gonadal development was investigated. Zn exposure induced growth improvement, but also led to gonadal dysfunction in the lined seahorse. Female seahorses exhibited high testosterone levels, immature follicles, and weight increase after Zn exposure, which is the typical characteristics of a polycystic ovary syndrome (PCOS)-like phenotype. Transcriptomic data suggested that the Zn-induced growth promotion resulted from the dysregulated expression of fat accumulation genes. Further investigation of gene expression profiles in the brain, ovaries, and testes indicated that Zn affected the expression of genes involved in growth, immunity, tissue remodeling, and gonadal development by regulating serum steroid hormone levels and androgen receptor expression. This study not only clarifies the complex impact of Zn on seahorses using physiological, histological, and molecular evidence but can also provide new insights into the mechanism underlying PCOS in reproductive-aged women. Moreover, this work demonstrates the risk of the common practice of Zn supplementation in the aquaculture industry as the consequent growth yield may not represent a healthy condition.

Mass variations and transfer process of shrimp farming pollutants in aquaculture drainage systems: Effects of DOM features and physicochemical properties

The expansion of aquaculture produces increasing pollutant loads, necessitating the use of drainage systems to discharge wastewater into surface water. To assess the mass variations and transfer process of aquaculture wastewater, an entire aquaculture drainage investigation lasting for 48 h was conducted, focusing on the nutrients, heavy metals, dissolved organic matter (DOM), and physicochemical properties of drainage in a commercial shrimp farm. The findings revealed that early drainage produced more heavy metals, total nitrogen (TN), dissolved organic nitrogen (DON), and feed-like proteins from aquaculture floating feed and additives, whereas late drainage produced more PO43--P and total dissolved phosphorus (TP). A few pollutants, including DON, Cu, and feed-like proteins, were effectively removed, whereas the contents of TN, dissolved inorganic nitrogen, and Zn increased in the multi-level aquaculture drainage system. Limited dilution indicated that in-stream transfer was the main process shaping pollutant concentrations within the drainage system. In the lower ditches, NO3--N, heavy metals, and feed-like proteins exhibited evident in-stream attenuation, while TN and NH4+-N underwent significant in-stream enrichment processes, especially in ditch C, with the transfer coefficient values (vf) of -1.74E-5 and -2.04E-5. This indicates that traditional aquaculture drainage systems serve as nitrogen sinks, rather than efficient nutrient purge facilitators. Notably, DOM was identified as a more influential factor in shaping the in-stream transfer process in aquaculture drainage systems, with an interpretation rate 40.79% higher than that of the physiochemical properties. Consequently, it is necessary to eliminate the obstacles posed by DOM to pollutant absorption and net zero emissions in aquaculture drainage systems in the future. ENVIRONMENTAL IMPLICATIONS: Nutrients, heavy metals, and dissolved organic matter are hazardous pollutants originating from high-density aquaculture. As the sole conduit to natural waters, aquaculture drainage systems have pivotal functions in receiving and purifying wastewater, in which the in-stream transfer process is affected by ambient conditions. This field study investigated the spatial variations, stage distinctions, effects of physicochemical properties, and dissolved organic matter (DOM) features. This finding suggests that the aquaculture drainage system as a nitrogen sink and DOM source. While the DOM is the key factor in shaping the in-stream transfer process, and obstacles for pollutant elimination. This study helps in understanding the fate of aquaculture pollutants and reveals the drawbacks of traditional aquaculture drainage systems.

Effects of Dietary Zinc on Growth Performance, Digestive Enzyme Activities, Antioxidant Status, and Immune Responses of Sea Cucumber Apostichopus japonicus

Zinc is an essential micronutrient for organisms involved in regulating various biological processes. This study evaluated the effects of dietary zinc on growth performance, digestive enzyme activities, antioxidant status, and immune responses of sea cucumber Apostichopus japonicus. Five experimental diets were formulated with graded levels of zinc (0, 20, 40, 60, and 80 mg/kg, respectively), and the actual dietary zinc values were 31.4, 51.0, 68.2, 91.9, and 110.8 mg/kg diet, respectively. Sea cucumbers were fed with diets for 2 months. The results showed the growth performance, amylase, and trypsin activities of sea cucumber increased significantly with zinc supplementation, and the best growth performance and enzyme activities were observed at 40 mg/kg zinc diet. Zinc supplementation significantly increased activities of superoxide dismutase, catalase, anti-superoxide anion, and inhibiting hydroxyl radical, while significantly reduced the malondialdehyde content. Furthermore, the higher zinc supplementation levels resulted in significantly upregulated immune-related genes of hsp90, p105, rel, and lsz, suggesting that excessive zinc caused oxidative stress. The broken-line regression analysis of specific growth rate indicated dietary zinc requirement in juvenile sea cucumber was ~ 66.3 mg/kg diet. Overall, dietary zinc contributes to the growth and immune resistance of juvenile sea cucumber, and our study will provide insights into the rational use of dietary zinc in aquaculture.

Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet's technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome.

Dietary Copper Requirements for Aquatic Animals: A Review

Copper (Cu) is a vital microelement required for the optimum growth performance and wellbeing of aquatic animals. It contributed to various biological, physiological, and metabolic function in the entire body of the aquatic animals. Further, Cu is a cofactor for several enzymes involved in the antioxidation capacity and metalloenzyme formation. Some ingredients used for aquafeed formulation include sufficient amounts of Cu that can provide aquatic animals with their requirements. Nevertheless, in some cases, external Cu sources are needed to optimize the essential needs of aquatic animals. Inorganic, organic, and nano Cu forms are included in aquafeed and result in regulated physiological and biological functions. The addition of Cu should be added at particular doses considering the species, size, duration, and environmental conditions. Water-borne Cu level should also be considered as long as aquatic animals can obtain their requirements through gills to avoid overdosing and toxicity. Several studies reported the optimum doses of Cu required for optimal growth, productivity, and health status in several aquatic animals. This review article presents the up-to-date results of Cu-related studies in aquafeed. It also helps academia design further studies to better understand the border between Cu requirements and toxicity. Besides, planning for more studies involved in the understanding of the primary mode of action of Cu in aquatic animals' entire bodies.

Effects of Chromium-L-Methionine in Combination with a Zinc Amino Acid Complex or Selenomethionine on Growth Performance, Intestinal Morphology, and Antioxidative Enzymes in Red Tilapia Oreochromis spp

To consider diet optimization for the growth and health of fish under intensive aquaculture systems, with a focus on the farming of Nile tilapia and red tilapia in Thailand, we conducted an experiment based on a completely randomized design (CRD), with three treatments and four replicates. Three diets, supplemented with different trace minerals, were applied to selected groups of fish: (a) a control diet, without organic trace minerals supplementation; (b) a T1 diet of chromium-L-methionine at 500 ppb, in combination with a zinc amino acid complex at 60 parts per million (ppm); and (c) a T2 diet of chromium-L-methionine at 500 ppb in combination with selenomethionine at 300 ppb. Red tilapia with an initial mean weight of 190 ± 12 g/fish were randomly distributed into cages of 2 × 2 × 2.5 m in a freshwater pond (12 cages in total), with 34 fish per cage and a density of 17 fish/m3. During the 8 week feeding trial, the fish were fed 3−4% of their body weight twice a day. The fish were weighed, then blood samples were collected to study their immune responses. The intestines were collected, measured, and analyzed at the end of the feeding trial. The results showed that the red tilapia that were fed with diets of chromium-L-methionine in combination with a zinc amino acid complex in the T1 treatment had significantly (p < 0.05) higher final weights, weight gains, average daily gains (ADGs), and better feed conversion ratios (FCRs), compared with fish that were fed with the control diet without organic trace minerals and with fish that were fed with the T2 diet (p < 0.05). The midgut and hindgut villus heights of the group fed with chromium-L-methionine in combination with a zinc amino acid complex in the T1 treatment were significantly higher than those of the other groups (p < 0.05). The levels of the antioxidative enzyme superoxide dismutase (SOD) and lysozyme activity were not significantly different from those of fish that were fed with the control diet (p > 0.05), whereas the glutathione level tended to increase (p < 0.1) in fish that were fed with chromium-L-methionine in combination with selenomethionine in the T2 treatment. Therefore, we concluded that chromium-L-methionine in combination with a zinc amino acid complex or selenomethionine clearly enhanced red tilapia’s growth performance and feed utilization through the promotion of antioxidative enzyme activity and immune response.

The Assessment of Dietary Organic Zinc on Zinc Homeostasis, Antioxidant Capacity, Immune Response, Glycolysis and Intestinal Microbiota in White Shrimp (Litopenaeus vannamei Boone, 1931)

This study aimed to assess dietary organic zinc on zinc homeostasis, antioxidant capacity, immune response, glycolysis and intestinal microbiota in white shrimp (Litopenaeus vannamei Boone, 1931). Six experimental diets were formulated: Control, zinc free; S120, 120 mg·kg-1 zinc from ZnSO4·7H2O added into control diet; O30, O60, O90 and O120, 30, 60, 90 and 120 mg·kg-1 zinc from Zn-proteinate added into control diet, respectively. The results showed that organic zinc significantly promoted zinc content and gene expression of ZnT1, ZIP11 and MT in the hepatopancreas and enhanced antioxidant capacity and immunity (in terms of increased activities of T-SOD, Cu/Zn SOD, PO, LZM, decreased content of MDA, upregulated expressions of GST, G6PDH, ProPO, LZM and Hemo, and increased resistance to Vibrio parahaemolyticus). Organic zinc significantly upregulated GluT1 expression in the intestine, increased glucose content of plasma and GCK, PFK and PDH activities of hepatopancreas, and decreased pyruvate content of hepatopancreas. Organic zinc improved intestinal microbiota communities, increased the abundance of potentially beneficial bacteria and decreased the abundance of potential pathogens. Inorganic zinc (S120) also had positive effects, but organic zinc (as low as O60) could achieve better effects. Overall, organic zinc had a higher bioavailability and was a more beneficial zinc resource than inorganic zinc in shrimp feeds.