Zinc Supplements Boost Fish Growth, Health, Zinc Levels, and Enzyme Activity

Jim Crocker
20th March, 2025

Zinc Supplements Boost Fish Growth, Health, Zinc Levels, and Enzyme Activity

Rohu (Labeo rohita)

Photo adapted from: Utain Pummarin / CC BY (Source)

Key Findings

  • Researchers in Lahore, Pakistan discovered that adding zinc gluconate to rohu fish diets significantly boosts their growth and makes feed use more efficient
  • Fish fed with zinc gluconate absorbed more zinc, resulting in stronger bones and a healthier immune system
  • Zinc gluconate also helped the fish better manage stress and reduce harmful oxidative damage
Minerals are crucial for the health and growth of aquatic animals, playing a key role in their physiological and metabolic functions. Understanding how different minerals affect fish can lead to better farming practices and healthier aquatic populations. This is particularly important for species like Labeo rohita, commonly known as rohu, which is widely farmed for food in many parts of the world. Previous research has highlighted that aquatic animals need a balanced intake of minerals to thrive. Deficiencies or excesses in minerals such as calcium, phosphorus, magnesium, and trace elements like zinc can lead to various health problems in fish[2]. For instance, inadequate zinc levels can cause issues like reduced bone strength, poor appetite, and weakened immune systems. On the other hand, too much zinc can be toxic, disrupting the delicate balance that fish require to maintain their health. Zinc, in particular, has been recognized not only for its general nutritional importance but also for its role in immune function. Studies have shown that zinc helps regulate the immune system by controlling the availability of zinc within the body, which in turn affects the survival and activity of immune cells[3]. A deficiency in zinc can impair both the innate and adaptive immune responses, making fish more susceptible to diseases and increasing inflammation over time. Building on this foundation, a recent study conducted by the University of Veterinary and Animal Sciences in Lahore, Pakistan, investigated how different sources of zinc in the diet affect the growth and health of Labeo rohita[1]. The research aimed to determine which zinc supplement would best support the fish's development and overall well-being. In this study, researchers set up a controlled feeding trial with 300 rohu fish, each weighing approximately 15.84 grams. The fish were divided into five groups, each receiving a different zinc supplement: zinc sulfate (control), zinc citrate, zinc acetate, zinc monomethionine, and zinc gluconate. The concentrations of zinc varied across these supplements to assess their effectiveness and safety. After the trial period, the results were telling. Fish fed with zinc gluconate showed significantly better growth metrics, including higher final body weight, better feed conversion ratio (which measures how efficiently the fish convert feed into body mass), greater body weight gain, and improved sediment growth rate compared to the other groups. Notably, the zinc gluconate group also consumed less feed, indicating more efficient nutrient utilization. Interestingly, the initial body weight and survival rates of the fish were similar across all groups, suggesting that the differences observed were specifically due to the type of zinc supplement used. Further analysis revealed that fish fed with zinc gluconate had higher zinc levels in their tissues, indicating better absorption and retention of this mineral. This aligns with earlier findings that trace elements like zinc are essential for proper bone formation and immune function in fish[2][3]. The study also examined the antioxidant enzyme activity in the fish, which is a marker of how well the fish can manage oxidative stress. Oxidative stress occurs when there is an imbalance between free radicals and antioxidants in the body, leading to cell damage. The zinc gluconate group had lower levels of thiobarbituric acid reactive substances (TBARS), which are indicators of oxidative damage, and higher levels of key antioxidant enzymes like glutathione peroxidase, catalase, and superoxide dismutase. This suggests that zinc gluconate enhances the fish's ability to combat oxidative stress, promoting better overall health. Stress and immune responses were also assessed by measuring hematocrit (the proportion of red blood cells), cortisol (a stress hormone), and glucose levels. Fish fed with zinc gluconate had lower hematocrit, cortisol, and glucose levels, indicating reduced stress and a more robust immune response. Additionally, blood serum parameters such as alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase remained lower in the zinc gluconate group, further supporting its beneficial effects on fish health. These findings are significant because they build upon previous research that identified critical mineral requirements in fish and the adverse effects of mineral imbalances[2]. By demonstrating that zinc gluconate is a particularly effective source of zinc, this study provides practical insights for aquaculture practices. Farmers can use this information to choose the best zinc supplements, ensuring that their fish grow efficiently and remain healthy, thereby reducing the risk of disease and improving overall yields. Moreover, the study addresses environmental concerns related to mineral intake in aquaculture. Excess minerals from uneaten or undigested feed can lead to water pollution, which harms natural ecosystems. By identifying zinc sources that are more effectively absorbed by fish, such as zinc gluconate, the research suggests a way to minimize waste and reduce the environmental impact of fish farming[2]. In summary, the study from the University of Veterinary and Animal Sciences in Lahore provides valuable insights into the optimal use of zinc supplements in aquaculture. By comparing different zinc sources, the researchers found that zinc gluconate not only promotes better growth and health in Labeo rohita but also enhances their ability to manage stress and maintain a strong immune system. These findings help bridge the gap in knowledge about trace mineral requirements in fish and offer practical solutions for improving aquaculture practices, supporting both fish health and environmental sustainability[2][3].

NutritionBiochemAnimal Science

References

Main Study

1) Bioavailability of zinc from different organic zinc chelates and their effect on the growth, whole body, tissue zinc content, enzymes activity and proximate composition of L. rohita

Published 19th March, 2025

https://doi.org/10.1371/journal.pone.0314146

Related Studies

2) Nutrition and Metabolism of Minerals in Fish.

https://doi.org/10.3390/ani11092711

3) Zinc and its role in immunity and inflammation.

https://doi.org/10.1016/j.autrev.2014.11.008


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