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Volume 17, Issue 4 (2025)
3 2025, 17(4): 371-376 |
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Received: 2025/12/22 | Accepted: 2026/01/1 | Published: 2025/11/19
Received: 2025/12/22 | Accepted: 2026/01/1 | Published: 2025/11/19
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Hussein B A. Effects of Dietary Zinc on Serum Proteins, Liver Enzyme Activities, Oxidative Stress Markers, and Biochemical Parameters in Male New Zealand White Rabbits. 3 2025; 17 (4) :371-376
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Introduction
The interest in micronutrient nutrition with mineral supplementation has increased recently, given the importance of minerals in supporting productive performance, enhancing immunity, and strengthening the functions of vital organs [1]. Zinc plays a crucial role in many vital bodily reactions, as it is considered one of the symbiotic elements (Zn++) and cannot lose an electron; additionally, it does not participate in the respiratory chain [2]. Therefore, zinc is considered an essential nutrient in animal nutrition. Zinc plays a fundamental and pivotal role in the synthesis, formation, and activity of various enzymes in the body, including protein formation and tissue structure stabilization, as well as participating in oxidation–reduction reactions [3]. Zinc works as a cofactor in many protein amino acids, involving amino groups, carboxyl groups, and thiol groups, which underlie about 300 enzymatic reactions in the body that depend on zinc [4]. Therefore, it participates in the metabolism of carbohydrates, fats, and fatty acids in the construction of proteins and serves as a cofactor for the enzyme superoxide dismutase, an antioxidant that removes reactive oxygen species [5].
Recent studies have shown that zinc supplementation in rabbit feed is vital and can significantly enhance antioxidant status and liver function indicators [6]. A study using rabbits fed zinc supplements found that glutathione peroxidase (GPx) activity and total antioxidant capacity are significantly increased [7]. Abdel-Wareth et al. [8] showed that adding nano-zinc oxide (Nano-ZnO) to the diet of rabbits results in a reduction in liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as a reduction in cholesterol and triglycerides, suggesting a potential improvement in liver function and metabolism [9]. This was confirmed by Thomas et al. [10] that animals receiving high doses of zinc, as recommended, show reduced disease symptoms and increased immunity after 4-9 days of zinc gluconate doses. However, Skrajnowska & Bobrowska-Korczak [11] indicate that any zinc deficiency leads to dysfunctional immune cells, which is a serious indicator of the importance of zinc in combating some infectious and immune diseases, most notably cancer. Zinc protects many cell types from apoptosis resulting from oxidative stress, and plays an effective role in transmitting various signals in eukaryotic cells involved in the process of genetic transcription [12]. Advances in microfluidic and acoustofluidic technology have provided powerful in vitro platforms to study how disease and immune cells respond to complex microenvironments, which can rapidly generate three-dimensional multicellular spheroids, enabling controlled investigation of cell viability, aggregation, and response to biochemical factors [13]. Likewise, porous-gradient microfluidic chips have been designed to create stable chemotactic gradients within engineered matrices [14]. Such models illustrate how both trace elements and physical microenvironments can modulate cellular behavior, complementing in vivo approaches like the present rabbit study.
Zinc transporters also act as regulators of ion balance in physiological processes and as components of systems involved in the absorption and transport of some micronutrients, such as zinc’s entry into and exit from cells [15]. Therefore, the need for zinc varies depending on age, the physiological state of the body, body weight, and animal type (ruminant or monogastric). Zinc availability also varies with soil zinc content and its availability through green fodder [16]. A study conducted on laboratory rabbits recommends that the optimal zinc dose is approximately 0.08mg per day. In the United States, the recommended dose is 15mg per day for adult males and 12mg per day for adult females, with an additional 5mg per day in cases of heat stress and 2.5mg per day for females [17]. In Britain, the recommended doses are 9.5mg per day for males and 7mg per day for adult females. In Norway, the recommended doses are 9mg per day for adult males and 7mg per day for adult females, with the maximum permissible dose being 45mg per day, according to The Standing Nordic Committee on Food, 1996 [18]. However, determining the optimal levels of zinc supplementation in many studies, including chemical source, bioavailability, time course of application, and subsequent changes in hepatic enzymes, antioxidants, and carbohydrate metabolism [19], still requires further study in commercial animals and the effect on improving physiology and biochemical metabolism in rearing conditions, such as male New Zealand White rabbits. Therefore, this study was designed to examine how different supplemental levels of dietary zinc (6 and 9mg/kg feed) influence serum protein profile, hepatic enzyme activities, antioxidant markers, and selected blood biochemical indices in male New Zealand White rabbits.
Materials and Methods
Thirty laboratory-bred male New Zealand White rabbits, weighing approximately 1.5-2.0kg, were used in this experiment. The animals were housed individually in metal cages under standard room conditions (temperature 22-28°C) and observed daily throughout the 25-day experimental period. Before starting the treatments, all rabbits underwent a 7-day acclimation period, during which they were examined to ensure they were clinically healthy and free from gastrointestinal parasites. During this time, they received prophylactic treatment against internal and external parasites and common infectious diseases. Throughout the study, rabbits were offered a basal complete-concentrate diet formulated according to [20], with free access to feed and drinking water. After acclimation, the animals were randomly allocated into three experimental groups (n=10 per group). The control group received only the basal diet and plain drinking water. The intervention groups 1 and 2 received the same basal diet but were supplemented once daily with 6mg and 9mg zinc, respectively, for 25 consecutive days. On day 25, blood samples were collected from the jugular vein of each rabbit for subsequent biochemical analyses. Zinc was added to rabbit feed by dosing the animals, with the quantity and timing of addition determined according to Sloup et al. [21].
All biochemical determinations were carried out using a fully automated clinical chemistry analyzer (Smart model, Genotech, USA). Blood was collected from each rabbit into plain, anticoagulant-free tubes and left to clot at room temperature. The samples were then centrifuged, and the separated serum was transferred into clean tubes for analysis. Serum total protein, albumin and globulin concentrations were measured, together with glutamic pyruvic transaminase (GPT) and glutamic oxaloacetate transaminase (GOT) activities. In addition, key blood biochemical indices, including glucose, total cholesterol and serum urea concentrations, were quantified.
Data were analyzed statistically using a general linear model to assess the effects of the experimental parameters on the studied traits, using SAS (version 2019) software. One-way ANOVA was used to assess significant differences between means, followed by a post hoc multiple range test according to Saleem et al. [22], at the significance level p≤0.05.
Findings
Total protein showed a numerical increase in the intervention 2 group compared to the control and intervention group 2; however, these differences were not statistically significant (p>0.05). Albumin showed a similar pattern, with higher values in the intervention group 1 than in the other groups, but this difference was not statistically significant (p>0.05). Globulin levels showed no significant differences between the three groups (Table 1).
Table 1. Comparison of zinc effect on serum protein profile in male New Zealand White rabbits
GPT and GOT activities decreased in the intervention 2 group compared to the control and intervention 1 groups. Malondialdehyde (MDA) levels declined in the intervention 2 group compared to the intervention 1 group. Glutathione (GSH) concentrations were reduced in all zinc-supplemented intervention groups (Table 2).
Table 2. Effect of zinc on mean liver enzyme activities and oxidative stress marker levels in male New Zealand White rabbits
Blood glucose concentrations were observed to differ between the zinc-supplemented groups and the control group. Urea concentrations were elevated in the intervention 2 group compared to the other groups. Regarding cholesterol and lipoprotein biomarkers, the intervention 1 group showed decreased cholesterol levels and a significant increase in HDL levels compared to the controls, whereas cholesterol levels increased in the intervention 2 group, correlating with reduced HDL concentrations. LDL values varied between the experimental groups (Table 3).
Table 3. Mean serum levels of biochemical parameters in male New Zealand White rabbits receiving a dietary zinc supplementation
Discussion
This study examined the effect of dietary zinc on serum protein profile, hepatic enzyme activities, antioxidant markers, and selected biochemical indices in male New Zealand White rabbits. Diet-induced zinc supplementation at different doses led to changes in concentrations of serum proteins, liver enzyme activity, oxidative stress biomarkers, and blood parameters in male New Zealand White rabbits. These results confirm the essential role of zinc as a beneficial basic nutrient when administered in moderate doses, and as a potential metabolic stress when administered in high concentrations.
An increase in total protein and albumin was observed in the intervention 2 group (moderate zinc group), providing evidence that zinc may boost protein synthesis and support the notion that zinc participates in the regulation of protein metabolism and protects proteins from oxidative degradation in cell membranes [23]. Zinc can form complexes with amine, carboxyl and thiol groups in amino acids and proteins, which helps preserve protein structures and safeguard them from oxidative degradation within cellular membranes. Nearly 300 enzymatic reactions depend on its presence; for this reason, zinc is a structural and catalytic component of many enzymes involved in transcription, translation, and cell growth processes [23-25].
A similar pattern was observed in albumin, although the differences were not statistically significant; the consistent rising trend supports the physiological importance of zinc in regulating protein synthesis. Similar findings were reported by Brown et al. [26] and Harold [27], who showed that the presence of zinc is associated with optimized albumin synthesis and tissue anabolic activity. In this context, albumin is required for building body tissues and cells, including immune cells and hormone-related proteins, which could explain why albumin concentrations do not increase dramatically despite zinc supplementation [28].
Regarding globulin, no significant differences were detected between the three groups. The globulin-to-total protein ratio is an important indicator of immune status, as it reflects the functional state of the immune response; increased globulin levels indicate adequate immunoglobulin concentrations that help protect the body against pathogens [18]. The absence of differences among groups suggested that the zinc levels used were sufficient to maintain immune-related protein synthesis without markedly altering them. In addition, zinc plays a crucial structural and regulatory role in several proteins, peptides, and growth factors [29], which supports its importance for tissue development and immune efficiency.
Zinc supplementation demonstrated remarkable effects on several indicators of liver function and oxidative stress. The activities of GPT and GOT decreased in the group that received a high dose of zinc compared to the other groups, which suggests improved liver status and less hepatocellular damage. This is consistent with the results of Kucková et al. [7], who report that zinc can protect hepatic tissue by supporting antioxidant defense mechanisms and lowering oxidative stress indices, such as MDA. This is supported by Lawi et al. [30], who verify the pivotal antioxidant pathways and delineated that oxidative stress contributes to tissue injury via pathways, including lipid peroxidation. Accordingly, markers, such as MDA (lipid peroxidation) and GSH (non-enzymatic antioxidant capacity) are widely applied to indicate changes in oxidative balance and cytoprotection [31].
Regarding lipid peroxidation, MDA concentration was markedly reduced in the group that received a high dose of zinc compared to the moderate zinc group, which may indicate attenuated membrane lipid oxidation and enhanced redox homeostasis [32]. However, the relatively high standard deviations indicate notable inter-individual variability among rabbits, which could partly explain the inconsistent intergroup pattern [33]. Conversely, levels of GSH were reduced in all experimental groups, and the response to zinc was modest. This may be related to the short duration of the experiment or to supplementation levels that were not sufficient to boost a potent glutathione response [34]. Previous findings substantiate that zinc leads to an increase in glutathione accumulation and prompts antioxidant enzymes to induce GPx and SOD, particularly at supraphysiological concentrations or under conditions of heightened oxidative stress [35]. The present experimental outcome shows that zinc plays a role in decreasing hepatic enzyme activity and contributing to improved physiological efficacy. Nevertheless, the high variability in the measurements and the unclear trends for GSH and MDA suggest that further work using longer feeding periods and a wider range of zinc doses is required to clarify the antioxidant response.
Adding zinc to rabbit diets influenced several blood biochemical indices compared to the control group. A decrease in blood glucose concentration was observed in the zinc-supplemented experimental groups. This suggests that zinc contributed to improving carbohydrate metabolism, possibly through supporting enzymes involved in glucose homeostasis and enhancing glucose utilization in metabolic pathways. This outcome corroborates with Banaszak et al. [36], who demonstrate that zinc supplementation in rabbit diets is associated with reduced blood glucose concentrations.
Urea concentrations were elevated in the intervention 2 group compared to the other groups. This may indicate increased protein catabolism or a low-grade metabolic burden associated with the increased zinc level, and may additionally reflect a dose-related influence on renal handling of nitrogenous waste. This observation is consistent with that of Banaszak et al. [36], who suggest that an overdose of zinc may induce metabolic stress and alter biochemical biomarkers.
Accordingly, the effect of zinc depends on the dose, whereby moderate supplementation may enhance lipid metabolism, whereas an overdose intake may alter homeostasis toward less favorable alterations. Adequate dietary zinc consumption can contribute to lowering LDL and supporting HDL, whereas excessive concentrations may lead to adverse metabolic outcomes. In the present study, LDL values also varied between groups, with the higher zinc level showing a reduction, while a significant rise was observed in the second group, which reflects instability in lipid regulation and individual variability across experimental groups. A previous study showed that zinc supplementation improved blood lipid levels, particularly by lowering total cholesterol, LDL cholesterol, and triglycerides. These findings suggested that zinc contributed to reducing the risk of atherosclerosis and mortality [37].
Overall, zinc supplementation at a moderate dose supported improvements in several metabolic parameters, whereas the higher dose appears to exceed the optimal range and lead to undesirable changes in several measurements. This substantiates the importance of identifying an appropriate zinc dose that provides beneficial effects without causing adverse metabolic effects.
The present study provides evidence that dietary zinc supplementation modulated biochemical and physiological biomarkers in male New Zealand White rabbits in a dose-dependent manner. Moderate-dose supplementation led to improvements in serum total protein, albumin, and lipid profile, indicative of enhanced protein synthesis, antioxidant status, and metabolic health. The higher dose showed a significant reduction in serum GPT and GOT activities, consistent with improved hepatic function and attenuation of oxidative damage, although changes in GSH and MDA were relatively limited. Zinc supplementation was associated with reduced blood glucose concentrations, suggesting improved carbohydrate metabolism and insulin sensitivity. However, the higher dose induced slight elevations in serum urea and cholesterol, indicating that excessive zinc intake disturbs metabolic equilibrium. In summary, moderate zinc supplementation can support liver function and overall metabolic health in rabbits, but careful optimization of the dose is required to achieve physiological benefits while reducing potential side effects. Moreover, more work is needed to determine the optimal level of dietary zinc supplementation and to explore long-term consequences under different management and dietary conditions.
Conclusion
Moderate dietary zinc supplementation supports liver function and metabolic health in adult male rabbits while maximizing physiological benefits and minimizing potential adverse effects.
Acknowledgments: The author expresses sincere gratitude to Al-Manara University for supporting this research project and for providing the resources necessary to advance scientific research.
Ethical Permissions: All experimental procedures involving animals were conducted in accordance with internationally accepted ethical standards for animal care and use. The study protocol was reviewed and approved by the Institutional Scientific Committee of Al-Manara University for Medical Sciences, Maysan, Iraq.
Conflicts of Interests: The authors declared no conflicts of interests.
Authors' Contribution: Hussein BA (First Author), Introduction Writer/Methodologist/Main Researcher/Discussion Writer/Statistical Analyst (100%)
Funding/Support: This study was supported by Al-Manara University through laboratory facilities and institutional resources.
The interest in micronutrient nutrition with mineral supplementation has increased recently, given the importance of minerals in supporting productive performance, enhancing immunity, and strengthening the functions of vital organs [1]. Zinc plays a crucial role in many vital bodily reactions, as it is considered one of the symbiotic elements (Zn++) and cannot lose an electron; additionally, it does not participate in the respiratory chain [2]. Therefore, zinc is considered an essential nutrient in animal nutrition. Zinc plays a fundamental and pivotal role in the synthesis, formation, and activity of various enzymes in the body, including protein formation and tissue structure stabilization, as well as participating in oxidation–reduction reactions [3]. Zinc works as a cofactor in many protein amino acids, involving amino groups, carboxyl groups, and thiol groups, which underlie about 300 enzymatic reactions in the body that depend on zinc [4]. Therefore, it participates in the metabolism of carbohydrates, fats, and fatty acids in the construction of proteins and serves as a cofactor for the enzyme superoxide dismutase, an antioxidant that removes reactive oxygen species [5].
Recent studies have shown that zinc supplementation in rabbit feed is vital and can significantly enhance antioxidant status and liver function indicators [6]. A study using rabbits fed zinc supplements found that glutathione peroxidase (GPx) activity and total antioxidant capacity are significantly increased [7]. Abdel-Wareth et al. [8] showed that adding nano-zinc oxide (Nano-ZnO) to the diet of rabbits results in a reduction in liver aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as a reduction in cholesterol and triglycerides, suggesting a potential improvement in liver function and metabolism [9]. This was confirmed by Thomas et al. [10] that animals receiving high doses of zinc, as recommended, show reduced disease symptoms and increased immunity after 4-9 days of zinc gluconate doses. However, Skrajnowska & Bobrowska-Korczak [11] indicate that any zinc deficiency leads to dysfunctional immune cells, which is a serious indicator of the importance of zinc in combating some infectious and immune diseases, most notably cancer. Zinc protects many cell types from apoptosis resulting from oxidative stress, and plays an effective role in transmitting various signals in eukaryotic cells involved in the process of genetic transcription [12]. Advances in microfluidic and acoustofluidic technology have provided powerful in vitro platforms to study how disease and immune cells respond to complex microenvironments, which can rapidly generate three-dimensional multicellular spheroids, enabling controlled investigation of cell viability, aggregation, and response to biochemical factors [13]. Likewise, porous-gradient microfluidic chips have been designed to create stable chemotactic gradients within engineered matrices [14]. Such models illustrate how both trace elements and physical microenvironments can modulate cellular behavior, complementing in vivo approaches like the present rabbit study.
Zinc transporters also act as regulators of ion balance in physiological processes and as components of systems involved in the absorption and transport of some micronutrients, such as zinc’s entry into and exit from cells [15]. Therefore, the need for zinc varies depending on age, the physiological state of the body, body weight, and animal type (ruminant or monogastric). Zinc availability also varies with soil zinc content and its availability through green fodder [16]. A study conducted on laboratory rabbits recommends that the optimal zinc dose is approximately 0.08mg per day. In the United States, the recommended dose is 15mg per day for adult males and 12mg per day for adult females, with an additional 5mg per day in cases of heat stress and 2.5mg per day for females [17]. In Britain, the recommended doses are 9.5mg per day for males and 7mg per day for adult females. In Norway, the recommended doses are 9mg per day for adult males and 7mg per day for adult females, with the maximum permissible dose being 45mg per day, according to The Standing Nordic Committee on Food, 1996 [18]. However, determining the optimal levels of zinc supplementation in many studies, including chemical source, bioavailability, time course of application, and subsequent changes in hepatic enzymes, antioxidants, and carbohydrate metabolism [19], still requires further study in commercial animals and the effect on improving physiology and biochemical metabolism in rearing conditions, such as male New Zealand White rabbits. Therefore, this study was designed to examine how different supplemental levels of dietary zinc (6 and 9mg/kg feed) influence serum protein profile, hepatic enzyme activities, antioxidant markers, and selected blood biochemical indices in male New Zealand White rabbits.
Materials and Methods
Thirty laboratory-bred male New Zealand White rabbits, weighing approximately 1.5-2.0kg, were used in this experiment. The animals were housed individually in metal cages under standard room conditions (temperature 22-28°C) and observed daily throughout the 25-day experimental period. Before starting the treatments, all rabbits underwent a 7-day acclimation period, during which they were examined to ensure they were clinically healthy and free from gastrointestinal parasites. During this time, they received prophylactic treatment against internal and external parasites and common infectious diseases. Throughout the study, rabbits were offered a basal complete-concentrate diet formulated according to [20], with free access to feed and drinking water. After acclimation, the animals were randomly allocated into three experimental groups (n=10 per group). The control group received only the basal diet and plain drinking water. The intervention groups 1 and 2 received the same basal diet but were supplemented once daily with 6mg and 9mg zinc, respectively, for 25 consecutive days. On day 25, blood samples were collected from the jugular vein of each rabbit for subsequent biochemical analyses. Zinc was added to rabbit feed by dosing the animals, with the quantity and timing of addition determined according to Sloup et al. [21].
All biochemical determinations were carried out using a fully automated clinical chemistry analyzer (Smart model, Genotech, USA). Blood was collected from each rabbit into plain, anticoagulant-free tubes and left to clot at room temperature. The samples were then centrifuged, and the separated serum was transferred into clean tubes for analysis. Serum total protein, albumin and globulin concentrations were measured, together with glutamic pyruvic transaminase (GPT) and glutamic oxaloacetate transaminase (GOT) activities. In addition, key blood biochemical indices, including glucose, total cholesterol and serum urea concentrations, were quantified.
Data were analyzed statistically using a general linear model to assess the effects of the experimental parameters on the studied traits, using SAS (version 2019) software. One-way ANOVA was used to assess significant differences between means, followed by a post hoc multiple range test according to Saleem et al. [22], at the significance level p≤0.05.
Findings
Total protein showed a numerical increase in the intervention 2 group compared to the control and intervention group 2; however, these differences were not statistically significant (p>0.05). Albumin showed a similar pattern, with higher values in the intervention group 1 than in the other groups, but this difference was not statistically significant (p>0.05). Globulin levels showed no significant differences between the three groups (Table 1).
Table 1. Comparison of zinc effect on serum protein profile in male New Zealand White rabbits
GPT and GOT activities decreased in the intervention 2 group compared to the control and intervention 1 groups. Malondialdehyde (MDA) levels declined in the intervention 2 group compared to the intervention 1 group. Glutathione (GSH) concentrations were reduced in all zinc-supplemented intervention groups (Table 2).
Table 2. Effect of zinc on mean liver enzyme activities and oxidative stress marker levels in male New Zealand White rabbits
Blood glucose concentrations were observed to differ between the zinc-supplemented groups and the control group. Urea concentrations were elevated in the intervention 2 group compared to the other groups. Regarding cholesterol and lipoprotein biomarkers, the intervention 1 group showed decreased cholesterol levels and a significant increase in HDL levels compared to the controls, whereas cholesterol levels increased in the intervention 2 group, correlating with reduced HDL concentrations. LDL values varied between the experimental groups (Table 3).
Table 3. Mean serum levels of biochemical parameters in male New Zealand White rabbits receiving a dietary zinc supplementation
Discussion
This study examined the effect of dietary zinc on serum protein profile, hepatic enzyme activities, antioxidant markers, and selected biochemical indices in male New Zealand White rabbits. Diet-induced zinc supplementation at different doses led to changes in concentrations of serum proteins, liver enzyme activity, oxidative stress biomarkers, and blood parameters in male New Zealand White rabbits. These results confirm the essential role of zinc as a beneficial basic nutrient when administered in moderate doses, and as a potential metabolic stress when administered in high concentrations.
An increase in total protein and albumin was observed in the intervention 2 group (moderate zinc group), providing evidence that zinc may boost protein synthesis and support the notion that zinc participates in the regulation of protein metabolism and protects proteins from oxidative degradation in cell membranes [23]. Zinc can form complexes with amine, carboxyl and thiol groups in amino acids and proteins, which helps preserve protein structures and safeguard them from oxidative degradation within cellular membranes. Nearly 300 enzymatic reactions depend on its presence; for this reason, zinc is a structural and catalytic component of many enzymes involved in transcription, translation, and cell growth processes [23-25].
A similar pattern was observed in albumin, although the differences were not statistically significant; the consistent rising trend supports the physiological importance of zinc in regulating protein synthesis. Similar findings were reported by Brown et al. [26] and Harold [27], who showed that the presence of zinc is associated with optimized albumin synthesis and tissue anabolic activity. In this context, albumin is required for building body tissues and cells, including immune cells and hormone-related proteins, which could explain why albumin concentrations do not increase dramatically despite zinc supplementation [28].
Regarding globulin, no significant differences were detected between the three groups. The globulin-to-total protein ratio is an important indicator of immune status, as it reflects the functional state of the immune response; increased globulin levels indicate adequate immunoglobulin concentrations that help protect the body against pathogens [18]. The absence of differences among groups suggested that the zinc levels used were sufficient to maintain immune-related protein synthesis without markedly altering them. In addition, zinc plays a crucial structural and regulatory role in several proteins, peptides, and growth factors [29], which supports its importance for tissue development and immune efficiency.
Zinc supplementation demonstrated remarkable effects on several indicators of liver function and oxidative stress. The activities of GPT and GOT decreased in the group that received a high dose of zinc compared to the other groups, which suggests improved liver status and less hepatocellular damage. This is consistent with the results of Kucková et al. [7], who report that zinc can protect hepatic tissue by supporting antioxidant defense mechanisms and lowering oxidative stress indices, such as MDA. This is supported by Lawi et al. [30], who verify the pivotal antioxidant pathways and delineated that oxidative stress contributes to tissue injury via pathways, including lipid peroxidation. Accordingly, markers, such as MDA (lipid peroxidation) and GSH (non-enzymatic antioxidant capacity) are widely applied to indicate changes in oxidative balance and cytoprotection [31].
Regarding lipid peroxidation, MDA concentration was markedly reduced in the group that received a high dose of zinc compared to the moderate zinc group, which may indicate attenuated membrane lipid oxidation and enhanced redox homeostasis [32]. However, the relatively high standard deviations indicate notable inter-individual variability among rabbits, which could partly explain the inconsistent intergroup pattern [33]. Conversely, levels of GSH were reduced in all experimental groups, and the response to zinc was modest. This may be related to the short duration of the experiment or to supplementation levels that were not sufficient to boost a potent glutathione response [34]. Previous findings substantiate that zinc leads to an increase in glutathione accumulation and prompts antioxidant enzymes to induce GPx and SOD, particularly at supraphysiological concentrations or under conditions of heightened oxidative stress [35]. The present experimental outcome shows that zinc plays a role in decreasing hepatic enzyme activity and contributing to improved physiological efficacy. Nevertheless, the high variability in the measurements and the unclear trends for GSH and MDA suggest that further work using longer feeding periods and a wider range of zinc doses is required to clarify the antioxidant response.
Adding zinc to rabbit diets influenced several blood biochemical indices compared to the control group. A decrease in blood glucose concentration was observed in the zinc-supplemented experimental groups. This suggests that zinc contributed to improving carbohydrate metabolism, possibly through supporting enzymes involved in glucose homeostasis and enhancing glucose utilization in metabolic pathways. This outcome corroborates with Banaszak et al. [36], who demonstrate that zinc supplementation in rabbit diets is associated with reduced blood glucose concentrations.
Urea concentrations were elevated in the intervention 2 group compared to the other groups. This may indicate increased protein catabolism or a low-grade metabolic burden associated with the increased zinc level, and may additionally reflect a dose-related influence on renal handling of nitrogenous waste. This observation is consistent with that of Banaszak et al. [36], who suggest that an overdose of zinc may induce metabolic stress and alter biochemical biomarkers.
Accordingly, the effect of zinc depends on the dose, whereby moderate supplementation may enhance lipid metabolism, whereas an overdose intake may alter homeostasis toward less favorable alterations. Adequate dietary zinc consumption can contribute to lowering LDL and supporting HDL, whereas excessive concentrations may lead to adverse metabolic outcomes. In the present study, LDL values also varied between groups, with the higher zinc level showing a reduction, while a significant rise was observed in the second group, which reflects instability in lipid regulation and individual variability across experimental groups. A previous study showed that zinc supplementation improved blood lipid levels, particularly by lowering total cholesterol, LDL cholesterol, and triglycerides. These findings suggested that zinc contributed to reducing the risk of atherosclerosis and mortality [37].
Overall, zinc supplementation at a moderate dose supported improvements in several metabolic parameters, whereas the higher dose appears to exceed the optimal range and lead to undesirable changes in several measurements. This substantiates the importance of identifying an appropriate zinc dose that provides beneficial effects without causing adverse metabolic effects.
The present study provides evidence that dietary zinc supplementation modulated biochemical and physiological biomarkers in male New Zealand White rabbits in a dose-dependent manner. Moderate-dose supplementation led to improvements in serum total protein, albumin, and lipid profile, indicative of enhanced protein synthesis, antioxidant status, and metabolic health. The higher dose showed a significant reduction in serum GPT and GOT activities, consistent with improved hepatic function and attenuation of oxidative damage, although changes in GSH and MDA were relatively limited. Zinc supplementation was associated with reduced blood glucose concentrations, suggesting improved carbohydrate metabolism and insulin sensitivity. However, the higher dose induced slight elevations in serum urea and cholesterol, indicating that excessive zinc intake disturbs metabolic equilibrium. In summary, moderate zinc supplementation can support liver function and overall metabolic health in rabbits, but careful optimization of the dose is required to achieve physiological benefits while reducing potential side effects. Moreover, more work is needed to determine the optimal level of dietary zinc supplementation and to explore long-term consequences under different management and dietary conditions.
Conclusion
Moderate dietary zinc supplementation supports liver function and metabolic health in adult male rabbits while maximizing physiological benefits and minimizing potential adverse effects.
Acknowledgments: The author expresses sincere gratitude to Al-Manara University for supporting this research project and for providing the resources necessary to advance scientific research.
Ethical Permissions: All experimental procedures involving animals were conducted in accordance with internationally accepted ethical standards for animal care and use. The study protocol was reviewed and approved by the Institutional Scientific Committee of Al-Manara University for Medical Sciences, Maysan, Iraq.
Conflicts of Interests: The authors declared no conflicts of interests.
Authors' Contribution: Hussein BA (First Author), Introduction Writer/Methodologist/Main Researcher/Discussion Writer/Statistical Analyst (100%)
Funding/Support: This study was supported by Al-Manara University through laboratory facilities and institutional resources.
Keywords:
References
1. Espinosa-Salas S, Gonzalez-Arias M. Nutrition: Micronutrient intake, imbalances, and interventions. Treasure Island, FL: StatPearls Publishing; 2023. [Link]
2. Ibrahim NK, Abd Almajeed M, Kadhum HJ. Essential role of zinc in human immunity: A subject review. Educ Med J. 2022;48(6):1-9. [Link]
3. Kokkali M, Dessen JE, Sveen L, Lefrancois A, Timmerhaus G, Kvamme E, et al. Dietary trace mineral (Cu, Fe, Mn, Zn, and Se) source and levels on production parameters, fillet quality, mineralization, and skin morphology of 1+ and 0+ Atlantic salmon across regions in Norway. Aquaculture. 2025;602:742375. [Link] [DOI:10.1016/j.aquaculture.2025.742375]
4. Stiles LI, Ferrao K, Mehta KJ. Role of zinc in health and disease. Clin Exp Med. 2024;24(1):38. [Link] [DOI:10.1007/s10238-024-01302-6]
5. Forrester SJ, Kikuchi DS, Hernandes MS, Xu Q, Griendling KK. Reactive oxygen species in metabolic and inflammatory signaling. Circ Res. 2018;122(6):877-902. [Link] [DOI:10.1161/CIRCRESAHA.117.311401]
6. Serra V, Castrica M, Agradi S, Curone G, Vigo D, Di Giancamillo A, et al. Antioxidant activity of different tissues from rabbits fed dietary bovine colostrum supplementation. Animals. 2023;13(5):850. [Link] [DOI:10.3390/ani13050850]
7. Kucková K, Grešáková LU, Takácsová M, Kandričáková A, Chrastinová LU, Polačiková M, et al. Changes in the antioxidant and mineral status of rabbits after administration of dietary zinc and/or thyme extract. Front Vet Sci. 2021;8:740658. [Link] [DOI:10.3389/fvets.2021.740658]
8. Abdel-Wareth AA, Ali AH, Amer SA, Younis EM, Abdel-Warith AA, Kassim ASN, et al. Effects of dietary supplementation with zinc oxide or selenium nanoparticles and their combination on rabbit productive performance, nutritional and physiological responses. Ital J Anim Sci. 2024;23(1):1258-68. [Link] [DOI:10.1080/1828051X.2024.2391550]
9. Barakat MAE, El-Manylawi MAF, Refaie AM. Impact of dietary zinc sources and levels on growth performance and immune response in fattening rabbits. Egypt J Vet Sci. 2025:1-9. [Link] [DOI:10.21608/ejvs.2025.337813.2507]
10. Thomas S, Patel D, Bittel B, Wolski K, Wang Q, Kumar A, et al. Effect of high-dose zinc and ascorbic acid supplementation vs usual care on symptom length and reduction among ambulatory patients with SARS-CoV-2 infection: The COVID A to Z randomized clinical trial. JAMA Netw Open. 2021;4(2):e210369. [Link] [DOI:10.1001/jamanetworkopen.2021.0369]
11. Skrajnowska D, Bobrowska-Korczak B. Role of zinc in immune system and anti-cancer defense mechanisms. Nutrients. 2019;11(10):2273. [Link] [DOI:10.3390/nu11102273]
12. Shati AA, Al-Taee HS, Saleem HD. Ser-surveying of caprine Q-fever (Coxiella burnetii) in milk. REDVET. 2022;23(3):467-78. [Link]
13. AlHasan L, Qi A, Al-Aboodi A, Rezk A, Shilton RR, Chan PP, et al. Surface acoustic streaming in microfluidic system for rapid multicellular tumor spheroids generation. Proc SPIE. 2013;8923:828-31. [Link] [DOI:10.1117/12.2034050]
14. Al-Abboodi A, Tjeung R, Doran P, Yeo L, Friend J, Chan P. Microfluidic chip containing porous gradient for chemotaxis study. Proc SPIE. 2011;8204:219-24. [Link] [DOI:10.1117/12.904870]
15. Kambe T, Taylor KM, Fu D. Zinc transporters and their functional integration in mammalian cells. J Biol Chem. 2021;296:100320. [Link] [DOI:10.1016/j.jbc.2021.100320]
16. Roohani N, Hurrell R, Kelishadi R, Schulin R. Zinc and its importance for human health: An integrative review. J Res Med Sci. 2013;18(2):144-57. [Link]
17. Saleem HD, Alfarras F, Hameed NM, Al-Zubaidi SH, Ali MS, Hamood SA, et al. Detection of Salmonella spp. by traditional and PCR assays in raw milk, Maysan, Iraq. Arch Razi Inst. 2022;77(4):1453-7. [Link]
18. Milman NT. Dietary iron intakes in men in Europe are distinctly above the recommendations: A review of 39 national studies from 20 countries in the period 1995-2016. Gastroenterol Res. 2020;13(6):233-45. [Link] [DOI:10.14740/gr1344]
19. He X, Chen A, Liao Z, Zhang Y, Lin G, Zhuang Z, et al. Diet supplementation of organic zinc positively affects growth, antioxidant capacity, immune response and lipid metabolism in juvenile largemouth bass, Micropterus salmoides. Br J Nutr. 2023;130(10):1689-703. [Link] [DOI:10.1017/S0007114523000909]
20. Salami H, Hamza T, Saleem H, Fadhil A, Abdulhasan M, Adhab A, et al. Efficiency of purified laccase from Pseudomonas spp. as bioremediator agent in gasoline contaminated soils. Int J Pharm Qual Assur. 2022;13(2):141-4. [Link]
21. Sloup V, Jankovská I, Nechybová S, Peřinková P, Langrová I. Zinc in the animal organism: A review. SCIENTIA AGRICULTURAE BOHEMICA. 2017;48(1):13-21. [Link] [DOI:10.1515/sab-2017-0003]
22. Saleem H, Al-Obaidi A, Al-Tmemy WB. Histopathological changes due to toxic effect of aflatoxin B1 on liver, kidney and therapeutic/preventive role of camel milk. Biochem Cell Arch. 2021;21(1):741-9. [Link]
23. Barbara M, Mindikoglu AL. The role of zinc in the prevention and treatment of nonalcoholic fatty liver disease. Metab Open. 2021;11:100105. [Link] [DOI:10.1016/j.metop.2021.100105]
24. Ateya RH, Taha NM, Mandour AEA, Lebda MA, El-Morshedy AM. Effect of monosodium glutamate and sodium nitrite on some biochemical parameters in Japanese quails. Alex J Vet Sci. 2016;48(1):107-14. [Link] [DOI:10.5455/ajvs.197829]
25. Prasad AS. Discovery of zinc for human health and biomarkers of zinc deficiency. In: Molecular, genetic, and nutritional aspects of major and trace minerals. Cambridge: Academic Press; 2017. p. 241-60. [Link] [DOI:10.1016/B978-0-12-802168-2.00020-8]
26. Brown KH, Wuehler SE, Peerson JM. The importance of zinc in human nutrition and estimation of the global prevalence of zinc deficiency. Food Nutr Bull. 2001;22(2):113-25. [Link] [DOI:10.1177/156482650102200201]
27. Harold HS. Zinc in human health. In: Biomedical and health research (Volume 76). Amsterdam: IOS Press; 2011. [Link]
28. Moman RN, Gupta N, Varacallo MA. Physiology, albumin. Treasure Island (FL): StatPearls Publishing; 2022. [Link]
29. Costa MI, Sarmento-Ribeiro AB, Gonçalves AC. Zinc: From biological functions to therapeutic potential. Int J Mol Sci. 2023;24(5):4822. [Link] [DOI:10.3390/ijms24054822]
30. Lawi ZK, Merza F, Banoon S, Al-Saady M, Al-Abboodi A. Mechanisms of antioxidant actions and their role in many human diseases: A review. J Chem Health Risks. 2021;11:45-57. [Link]
31. Mousavi SM, Hajishafiee M, Clark CCT, Nascimento IJBD, Milajerdi A, Amini MR, et al. Clinical effectiveness of zinc supplementation on the biomarkers of oxidative stress: A systematic review and meta-analysis of randomized controlled trials. Pharmacol Res. 2020;161:105166. [Link] [DOI:10.1016/j.phrs.2020.105166]
32. Cordiano R, Di Gioacchino M, Mangifesta R, Panzera C, Gangemi S, Minciullo PL. Malondialdehyde as a Potential Oxidative Stress Marker for Allergy-Oriented Diseases: An update. Molecules. 2023;28(16):5979. [Link] [DOI:10.3390/molecules28165979]
33. Skowron M, Zalejska-Fiolka J, Błaszczyk U, Chwalińska E, Owczarek A, Birkner E. Antioxidant enzyme activities in rabbits under oxidative stress induced by high fat diet. J Vet Res. 2018;62(2):199-206. [Link] [DOI:10.2478/jvetres-2018-0019]
34. Giustarini D, Milzani A, Dalle-Donne I, Rossi R. How to increase cellular glutathione. Antioxidants. 2023;12(5):1094. [Link] [DOI:10.3390/antiox12051094]
35. Marreiro DDN, Cruz KJC, Morais JBS, Beserra JB, Severo JS, De Oliveira ARS. Zinc and oxidative stress: Current mechanisms. Antioxidants. 2017;6(2):24. [Link] [DOI:10.3390/antiox6020024]
36. Banaszak M, Górna I, Przysławski J. Zinc and the innovative zinc-α2-glycoprotein adipokine play an important role in lipid metabolism: A critical review. Nutrients. 2021;13(6):2023. [Link] [DOI:10.3390/nu13062023]
37. Ranasinghe P, Wathurapatha WS, Ishara MH, Jayawardana R, Galappatthy P, Katulanda P, et al. Effects of zinc supplementation on serum lipids: A systematic review and meta-analysis. Nutr Metab. 2015;12:26. [Link] [DOI:10.1186/s12986-015-0023-4]
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