Bioaccumulation and Toxicity Studies of Lead and Mercury in Laying Hens: Effects on Laying Performance, Blood Metabolites, Egg Quality and Organ Parameters

Concentrations, Sources, and Health Risk of Heavy Metals in Edible Parts of Broilers from Northeast of Algeria

Heavy metals contamination of poultry products is a major concern for public health. This study aimed to determine the concentration of mercury (Hg), lead (Pb), and iron (Fe) in the edible parts of broilers, as well as in feed, drinking water, and litter as sources of contamination and to assess their possible human health risk in the province of Jijel (Northeast Algeria). The range of Hg, Pb, and Fe in edible parts were 0.004-0.007, 0.185-0.480, and 28.536-88.306 mg/kg, respectively, and the difference in content was only significant (p < 0.05) for lead. Breast and thigh samples had Pb concentrations above the maximum limit. Spearman coefficient analysis revealed that most correlations were positive between metals detected in feed, water, and litter and those in the edible parts of broilers. But most of them were insignificant (p > 0.05). The estimated daily intake (EDI) values of examined metal exceeded the tolerable daily intake (PTDI). The target hazard quotients (THQ) and hazard index (HI) of all metals were lower than 1, suggesting no significant carcinogenic risks. The calculated incremental lifetime cancer risk (ILCR) of Pb was higher than 10-4 for men, women, and children, indicating the presence of carcinogenic risk. Considering the wide consumption of broiler meat, regular national monitoring of heavy metals in the broiler production chain is recommended to protect population health.

Content of Toxic Elements (Arsenic, Cadmium, Mercury, Lead) in Eggs from an Ethically Managed Laying Hen Farm

Domestic chicken farming has been promoted and spread in several Italian municipalities and worldwide as an aid to the self-consumption of domestically produced food. This study investigated the levels of four toxic elements (As, Cd, Hg, and Pb) in eggs from an ethical laying hen farm, comparing the element concentrations with those possibly present in supermarket eggs. A total of 201 eggs, 141 from the farm and produced by different hen genotypes, and 60 from the supermarket, were collected. The levels of the toxic elements were evaluated in the yolk, albumen, and eggshells of all eggs. The results show that the supermarket eggs' yolk and albumen were more contaminated with lead, compared to the rural eggs. Contrarily, the mean content of arsenic was higher in the albumen and eggshells of the rural eggs, compared to the supermarket eggs. The cadmium content was below the LOQ (0.005 mg/kg) in all samples. The mercury content was below or around the LOQ in all rural eggs. Overall, the supermarket egg albumens were significantly more contaminated than the rural ones. No significant differences were found in quality parameters for both types of eggs. The toxic element values that were detected were in line with other studies in the literature. However, despite the concentrations found not representing a risk to the consumers' health, the results of this study raise a potential food safety issue, and it would be desirable to set specific MRLs for eggs for consumers' protection.

Effects of cadmium, lead, mercury, chromium, and selenium co-treatment on egg quality and fatty acids

This study aimed to reveal the effect of selenium (Se) and heavy metals (chromium (Cr), cadmium (Cd), lead (Pb), and mercury (Hg)) on the quality, fatty acids, and 13 kinds of ions in the egg yolk and albumen. Four experimental groups were established, including a control group (control; basal diet), Se group (basal diet + Se), heavy metals group (basal diet + CdCl₂ + Pb(NO₃)₂ + HgCl₂ + CrCl₃), and Se + heavy metal (HM) group (basal diet + Se + CdCl₂ + Pb(NO₃)₂ + HgCl₂ + CrCl₃). Se supplementation significantly increased the experimental egg yolk percentage since Se accumulation mainly occurred in the yolks of the eggs. The Cr content in the yolks of the Se + heavy metal groups decreased at 28 days, while a significant reduction was evident in the Cd and Hg levels of the Se + heavy metal yolks compared to the heavy metal group at 84 days. The complex interactions between the elements were analyzed to determine the positive and negative correlations. Se displayed a high positive correlation with Cd and Pb in the yolk and albumen, while the heavy metals minimally affected the fatty acids in the egg yolk.

Protective effects of selenized yeast on the combination of cadmium-, lead-, mercury-, and chromium-induced toxicity in laying hens

The objective of this study was to investigate the toxic effects of a combination of cadmium (Cd), lead (Pb), mercury (Hg), and chromium (Cr) on laying performance, egg quality, serum biochemical parameters, and oxidative stress of laying hens, as well as the alleviating action of dietary supplementation of selenized yeast. A total of 160 Lohmann pink-shell laying hens (63-week-old) were randomly divided into four treatments with 10 replicates of four hens each. The treatments were the corn–soybean meal basal diet (control; CON), the CON diet supplemented with 0.4 mg selenium (Se)/kg from selenized yeast (Se); combined heavy metals group: the basal diet supplemented with 5 mg Cd/kg, 50 mg Pb/kg, 3 mg Hg/kg, and 5 mg Cr/kg (HEM), and the HEM diet supplemented with 0.4 mg Se/kg from selenized yeast (HEM+Se). The experimental period lasted for 12 weeks. The HEM diet decreased hen-day egg production, feed conversion ratio (FCR), and egg white quality (P < 0.05), but increased (P < 0.05) glutamic oxalacetic transaminase (AST) activity in the serum. HEM induced higher malondialdehyde (MDA) and reactive oxygen species (ROS) in the serum, liver, and ovary and significantly decreased (P < 0.05) the activity of total superoxide dismutase (SOD) and tended to decrease glutathione S-transferase (GST) (P = 0.09) in the serum. Meanwhile, HEM significantly decreased (P < 0.05) activity of SOD, GST, glutathione peroxidase (GPX), and glutathione (GSH) in the liver, and the activity of GPX and GSH in the ovary. Se addition of 0.4 mg/kg significantly (P < 0.05) improved hen-day egg production and FCR and decreased AST concentration and increased some enzyme activity in the serum, liver, and ovary. In conclusion, dietary HEM exposure depressed laying performance, and egg white quality was likely due to an impaired antioxidant capacity, disrupted hepatic function, and elevated HEM accumulation in the egg yolk and egg white of laying hens. Se addition of 0.4 mg/kg ameliorated toxic effects of HEM on laying performance, oxidative stress, and hepatic function.

Dose-dependent effect of chronic exposure to lead acetate on the dynamics of the content of delta-aminolevulinic acid and essential trace elements in the serum of laying hens

  One of the most global and dangerous pollutants is considered to be lead, due to its ability to accumulate in living organisms, to be included in the metabolic cycle, to form highly toxic organometallic compounds, not being biodegradable. To study the chronic effects of lead acetate, an experiment was performed on laying hens of Lohmann Brown cross. For research, one control and three experimental groups were formed, 20 chickens in each. Birds of the experimental groups were administered lead acetate daily with compound feed in doses (in terms of metal): Group I – 50 mg/kg of feed, II – 75 mg/kg of feed, III – 150 mg/kg of feed. Access to water was not restricted. The birds of the control group received a complete diet without lead acetate. On the 30th, 90th, 120th days of the experiment and the 20th day after withdrawal of the toxicant (the 140th day of the experiment), we took blood samples from birds for biochemical and toxicological studies. The concentration of delta-aminolevulinic acid (δ-ALA) in the serum of laying hens was determined by reversed-phase high-performance liquid chromatography. Determination of the content of lead in the serum of laying hens was performed by X-ray fluorescence analysis. The concentration of total calcium, inorganic phosphorus, and magnesium in the serum of the laying hens was determined using production kits. We detected the dose-dependent chronic effect of lead acetate on the dynamics of the content of delta-aminolevulinic acid and essential trace elements in the serum of laying hens. The administration of lead acetate into the body of productive poultry for 120 days in doses of 50, 75, and 150 mg/kg with feed did not cause visible clinical signs of poisoning, but caused a violation of porphyrin metabolism, manifested in a reliable increase in the concentration of delta-aminolevulinic acid in serum on the 30th, 90th and 120th days of the experiment. It has been experimentally proven that the administration into the body of laying hens of lead acetate in doses of 50, 75 and 150 mg/kg of feed for 120 days leads to the maximum accumulation of lead in the serum on the 30th, 90th, and 120th days of the experiment. Prolonged administration of lead acetate to laying hens at high concentrations is characterized by a reliable decrease in the content of total calcium, inorganic phosphorus and magnesium in the serum of laying hens and a reliable increase in the content of ferrum. In the future it is necessary to study the intensity of lipid peroxidation processes in laying hens under chronic exposure to lead acetate.

Ellagic acid plays an important role in enhancing productive performance and alleviating oxidative stress, apoptosis in laying quail exposed to lead toxicity

Lead (Pb) is one of the most toxic heavy metal environmental pollutants due to its widespread use of the industry and it is a harmful substance for human and animal health. This study was conducted to investigate the potential protective effects of ellagic acid (EA) on performance, egg quality, antioxidant parameters, and apoptotic pathway proteins in laying quails exposed to Pb toxicity. A total of 168 (15-week old) laying quails (Coturnix coturnix Japonica) were divided into 6 experimental groups (with similar initial average body weight). Birds were fed 1 of 6 diets for 8 weeks: 1 - Control (basal diet), 2 - Pb (basal diet + 100 mg/kg Pb), 3 - EA-300 (basal diet + 300 mg/kg EA), 4 - EA-500 (basal diet + 500 mg/kg EA), 5 - Pb + EA-300 (basal diet + 100 mg/kg Pb + 300 mg/kg EA), 6 - Pb + EA-500 (basal diet + 100 mg/kg Pb + 500 mg/kg EA). The results showed that adding 100 mg/kg of Pb to basal diet was adversely affected the performance parameters and, feed intake and egg production were significantly decreased by Pb supplementation (P < 0.01). However, the EA supplementation to Pb groups improved the performance parameters. Compared with the Pb alone group, in Pb + EA-500 group increased egg production by 8.4%. There were no significant differences in the Haugh unit, albumen index, and yolk index among groups (P > 0.05). Liver and kidney tissues of Pb group malondialdehyde (MDA) level increased (P < 0.001) and, GSH, GSH-Px, and CAT values decreased (P < 0.001) but, EA supplementation alleviated this condition (P < 0.001). The protein levels of caspase-3 and -9 were significantly increased in the Pb group compared to the control group, whereas EA supplementation alleviated the Pb-induced apoptosis by decreasing caspase-3 and -9 levels in the liver tissue (p < 0.001). In laying quails exposed to Pb toxicity, EA supplementation improves the performance parameters, enhances the antioxidant defense system, and suppresses apoptosis via regulates the expression of caspase-3 and -9. Thus, it was concluded that EA (especially 500 mg/kg) can ameliorate the toxic effects of Pb exposure in quails.

Bi-enzymes treatments attenuate cognitive impairment associated with oxidative damage of heavy metals

Oxidative stress has been implicated in the pathogenesis of cognitive impairment. Lead (Pb) is a common environmental toxicant and plays a vital role in oxidative stress activation. In this study, a superoxide dismutase (SOD) and catalase (CAT) containing poly (lactic-co-glycolic acid) (PLGA) meso-particles (PLGA@SOD-CAT) were prepared to attenuate cognitive impairment via inhibiting oxidative stress in rats. It was prepared using a double emulsion (water/oil/water phase) technique to minimize the hazardous effects of Pb burden on cognitive impairment. The meso-particles antagonized the Pb-induced cognitive impairments. Behaviour, serum biochemical parameters and biomarkers of oxidative stress in rats were evaluated after they were subjected to intravenous injection with lead nitrate and PLGA@SOD-CAT. Moreover, the potential protective mechanism of PLGA@SOD-CAT was determined. Notably, PLGA@SOD-CAT appreciably agented memory impairment caused by lead nitrate and it could significantly inhibit Pb-induced oxidative stress in the blood. Furthermore, a remarkable reversion effect of cognitive impairments, including escape latency, crossing platform times and time per cent during the platform quadrant, after PLGA@SOD-CAT administration were noted. Therefore, these results suggested that the bi-enzymes platform was a superior product in eliminating Pb-induced cognitive impairments through reducing expression of Pb-associated oxidative stress, and it could potentially be applied in detoxifying heavy metals in blood circulation.