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

Abstract

This study investigated bioaccumulation and toxicity derived from heavy metals in laying hens. The 160 52week old laying hens were divided into 5 treatments with 8 replicates of 4 birds per pen. The treatments consisted of the control diet (without heavy metals), control diet with half the available dosage (AD, 5 ppm lead and 0.2 ppm mercury), AD (10 ppm lead and 0.4 ppm mercury), 2-fold AD (20 ppm lead and 0.8 ppm mercury), and 3-fold AD (30 ppm lead and 1.2 ppm mercury), and were provided to the laying hens for 8 weeks. Food and water were provided on an ad libitum basis at all times. Body weight and food intake were recorded once every two weeks, and eggs were collected and recorded daily. Two birds from each pen were euthanized to collect blood and organ samples on week 4 and 8. The 3-fold AD diet reduced food intake compared to that of the control and AD diets (P＜0.05). Hens fed the half AD diet had darker yolk compared to those fed the control and AD diet on week 4 (P＜0.05). Hens fed the 2-and 3-fold AD diets had increased relative liver weight, blood glutamic pyruvic transaminase and glutamic oxaloacetic transaminase levels (P＜0.05), while F1 follicle weights decreased on week 4 and 8. No difference was found in egg production rate, egg quality, ovarian follicle, blood metabolites including protein, globulin, albumin, and urea nitrogen throughout the study (P＞0.05). Heavy metal concentrations in the liver, eggs, and feathers were not detected at both week 4 and 8. Our results indicate that in-feed heavy metals for layer diets up to 30 ppm of lead and 1.2 ppm of mercury brought on hepatic dysfunction increasing blood metabolites that are associated with liver inflammation.

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

“…The quantitative content of lead in the blood reflects the level of load on the body with its compounds, and the distribution of lead in the organs and tissues of animals depends on the intensity of blood circulation and affinity for metal (Kim et al, 2019;Wang et al, 2021). The results of our studies confirm that the determination of delta-aminolevulinic acid in the serum of poultry is necessary for the timely detection and correction of metabolic disorders caused by low doses of xenobiotics.…”

“…Numerous current studies are devoted to the mechanisms of toxic effects of lead ions on animals and birds (Kim et al, 2019;Oladipo et al, 2020). The special danger of the ecotoxicant is explained by its ability to be accumulated in living organisms, to be included in a metabolic cycle, to form highly toxic organometallic compounds not being subjected to biological decomposition.…”

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

“…However, some contrasting results were observed. Hg at 25–100 mg/kg as ethyl Hg chloride, and combination of Pb (30 mg/kg) and Hg (1.2 mg/kg) did not significantly depress egg quality of laying hens ( 16 , 28 ). Some previous studies have shown that organic or inorganic Cr had no effect or a slight increase in egg production ( 20 – 22 ).…”

“…Some reports have shown that the combined feeding of Pb and Cd leads to liver oxidative damage of laying hens ( 26 ) and decreased laying performance and egg quality ( 27 ). Kim et al ( 28 ) found that in-feed heavy metals for layer diets up to 30 mg Pb/kg and 1.2 mg Hg/kg decreased F 1 follicle weights simultaneously causing hepatic dysfunction as indicated by increasing blood metabolites that are associated with liver inflammation. Meanwhile, combined administration of methylmercury chloride (MeHgCl), lead acetate (PbAc), and cadmium chloride (CdCl 2 ) increased the severity of hepatic histopathologic changes and disturbed hepatic metal concentrations in Pekin ducks ( 29 , 30 ).…”

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

“…Besides, Pb is known as a ‘chemical time bomb' due to its toxicity which causes adverse effects on nervous and haemopoietic systems [ 10 ]. Children are particularly vulnerable to the neurotoxic effects of Pb exposure due to their developmental state, body weight and behaviours that increase the risk of exposure.…”