Heavy metal contamination of animal feedstuffs – a new survey

Emerging insights into the impacts of heavy metals exposure on health, reproductive and productive performance of livestock

Heavy metals, common environmental pollutants with widespread distribution hazards and several health problems linked to them are distinguished from other toxic compounds by their bioaccumulation in living organisms. They pollute the food chain and threaten the health of animals. Biologically, heavy metals exhibit both beneficial and harmful effects. Certain essential heavy metals such as Co, Mn, Se, Zn, and Mg play crucial roles in vital physiological processes in trace amounts, while others like As, Pb, Hg, Cd, and Cu are widely recognized for their toxic properties. Regardless of their physiological functions, an excess intake of all heavy metals beyond the tolerance limit can lead to toxicity. Animals face exposure to heavy metals through contaminated feed and water, primarily as a result of anthropogenic environmental pollution. After ingestion heavy metals persist in the body for an extended duration and the nature of exposure dictates whether they induce acute or chronic, clinical or subclinical, or subtle toxicities. The toxic effects of metals lead to disruption of cellular homeostasis through the generation of free radicals that develop oxidative stress. In cases of acute heavy metal poisoning, characteristic clinical symptoms may arise, potentially culminating in the death of animals with corresponding necropsy findings. Chronic toxicities manifest as a decline in overall body condition scoring and a decrease in the production potential of animals. Elevated heavy metal levels in consumable animal products raise public health concerns. Timely diagnosis, targeted antidotes, and management strategies can significantly mitigate heavy metal impact on livestock health, productivity, and reproductive performance.

Characterization of sargassum accumulated on Dominican beaches in 2021: Analysis of heavy, alkaline and alkaline-earth metals, proteins and fats

This paper presents the characterization of sargassum that reached the shores of eight Dominican beaches in 2021. The analysis of heavy, alkaline and alkaline-earth metals was performed by ICP-OES. Twelve heavy metals were studied, with the highest concentrations corresponding to Fe, As, and Zn. Regarding the alkaline and alkaline-earth metals, the highest concentrations were detected for Ca, K, Na and Mg. The high values of arsenic and alkali and alkaline-earth metal salts do not suggest using these algae in agriculture. It is recommended to carry out arsenic speciation studies to assess whether the form in which it is found is bioavailable for plants and animals. The heavy metal contamination index was determined, which ranged between 0.318 and 3.279. Finally, for the first time in the country, the organic fraction of sargassum was analyzed.

The accumulation of heavy metals in feeder insects and their impact on animal production

Insects have emerged as a novel feed protein source that could help to produce enough food to feed the growing global population. Good-quality protein content, minerals and bioactive compounds are the main reasons for the use of insects in livestock. Nonetheless, insects should be proven to be safe for use before being used as feeder insects for livestock. The accumulation of heavy metals in the feedstuff is becoming a major food safety concern, as this poses a serious problem to animal health and threatens human health through the transmission of toxic substances into the human food chain. It has been shown that feeder insects grown from agricultural waste materials contain chemical contaminants such as pesticides and veterinary drug residues. Current research mostly focuses on the safety evaluation of undesirable substances in edible insects for human consumption, but rarely indicates if these insects are safe to use in livestock feeds, particularly for avian species. Therefore, owing to the potential risks of heavy metal in animal production, heavy metal residues in feeder insects have received scientific attention. Hence, this review article is intended to evaluate and discuss selected heavy metals in insects, comparing them with toxicity limits for feedstuff of animal origin, and their potential risks of exposure. A literature search on metal elements present in insects was conducted using electronic databases. In addition, the citations included in articles were used to find other relevant articles or documents on this topic. Identified published articles were grouped and evaluated according to the insect species, growth stage and substrate from which the insects were grown. It was observed that the accumulation of heavy metals in insects is mainly associated with agricultural waste materials fed to insects. Furthermore, metal toxicity in animals varies according to animal species and age, metal type, concentration, and chemical form.

Trace Elements in Beef Cattle: A Review of the Scientific Approach from One Health Perspective

The objective was to investigate the context, approach and research topics present in the papers that analysed trace elements in beef cattle to identify gaps and scientific perspectives for the sustainable management of trace elements in livestock. The main research groups came from the United States, Spain, Japan, Brazil, India and Slovakia, which represented 31% of the papers produced. Only 37% of studies addressed aspects that integrated animal, environmental and human health. The reviewed papers concerned 56 elements and 15 bovine tissues (Cu, Zn, Pb, liver, muscle and kidney highlighted). The main gaps were (1) lack of research in developing countries, (2) the need to understand the impact of different environmental issues and their relationship to the conditions in which animals are raised, and (3) the need to understand the role of many trace elements in animal nutrition and their relationship to environmental and human health. Finally, we highlight possible ways to expand knowledge and provide innovations for broad emerging issues, primarily through expanding collaborative research networks. In this context, we suggest the adoption of the One Health approach for planning further research on trace elements in livestock. Moreover, the One Health approach should also be considered for managers and politicians for a sustainable environmental care and food safety.

Effects of Selenium Supplementation on the Ion Homeostasis in the Reproductive Organs and Eggs of Laying Hens Fed With the Diet Contaminated With Cadmium, Lead, Mercury, and Chromium

The objective of this study was to explore the toxic effects of different heavy metals in combination with their deposition and ion homeostasis in the reproductive organs and eggs of laying hens, as well as the alleviating action of selenized yeast. A total of 160 Lohmann pink-shell laying hens (63-week-old) were randomly allocated into four treatments with 10 replicates of four hens each. The four dietary treatments were the corn-soybean meal basal dietary (control; CON); the CON dietary supplemented with 0.4 mg/kg selenium from selenized yeast (Se); the CON dietary supplemented with 5 mg/kg Cd + 50 mg/kg Pb +3 mg/kg Hg + 5 mg/kg Cr (HEM), and the HEM dietary supplemented with 0.4 mg/kg selenium from selenized yeast (HEM+Se). The dietary HEM significantly increased Cd, Pb, and Hg deposition in the egg yolk and ovary, and Cd and Hg deposition in the oviduct and in the follicular wall (p < 0.05). The HEM elevated Fe concentration in the egg yolk, ovary, and oviduct (p < 0.05). The HEM decreased Mn concentration in the egg yolk, Fe, Mn, and Zn concentrations in the egg white, Cu concentration in the ovary, Mg concentration in the oviduct, as well as Ca, Cu, Zn, and Mg concentrations in the follicular walls (p < 0.05). Dietary Se addition elevated Se concentration in the egg yolk, oviduct, and follicular walls and Mg concentration (p < 0.05) in the oviduct, whereas it reduced Fe concentration in the oviduct compared with the HEM-treated hens. Some positive or negative correlations among these elements were observed. Canonical Correlation Analysis showed that the concentrations of Pb and Hg in the egg yolk were positively correlated with those in the ovary. The concentration of Cd in the egg white was positively correlated with that in the oviduct. In summary, dietary Cd, Pb, Hg, and Cr in combination caused ion loss and deposition of HEM in reproductive organs of laying hens. Dietary Se addition at 0.4 mg/kg from selenized yeast alleviated the negative effects of HEM on Fe and Mg ion disorder in the oviduct and follicle wall of hens.

Assessment of Pb, Cd, As and Hg concentration in edible parts of broiler in major metropolitan cities of Tamil Nadu, India

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Pb exceeded maximum residue limit in meat and liver in all 5 cities of Tamil Nadu state of India while kidney and neck samples of Chennai alone exceeded maximum residue limit.

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As was found to be exceeding maximum residue limit in breast (0.1 mg/kg) and liver (0.5 mg/kg) samples in many metropolitans of Tamil Nadu state.

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Cd and Hg concentration was within the maximum residue limit in all metropolitan samples.

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Daily dietary consumption of Pb, Cd, As and Hg from edible parts of chicken in Tamil Nadu metropolitans was well within the permitted quantity.

The risk of heavy metals contamination in meat and meat products is of great concern for both food safety and from human health point of view. The present study was carried out to assess the heavy metal residues such as Pb, Cd, As and Hg in broiler chicken meat, neck and edible organs (liver and kidney). In the present study, 150 samples were randomly collected from major cities (Chennai, Coimbatore, Madurai, Trichy, and Salem) of Tamil Nadu state, India and analyzed for Pb, Cd, As and Hg residues (mg/kg) using inductively coupled plasma-mass spectrometry (ICP-MS) technique. The results revealed that lead (Pb) concentration was higher in meat and liver samples of all cities and the highest concentration was detected in Chennai followed by Coimbatore, whereas in kidney and neck samples, Chennai metropolitan alone exceeded the MRL value of 0.5 and 0.1 mg/kg respectively. The residues of cadmium and mercury in meat and meat samples were within the permissible limit in all the metropolitans. Arsenic was found exceeding the MRL of 0.1 mg/kg in the breast samples of all the metropolitans (0.2141–2.2285 mg/kg, the highest being in Trichy), except for Madurai, which recorded very low value (0.0239 mg/kg). Arsenic was found in the range of 0.1110–1.0850 mg/kg in liver samples thus exceeding MRL value. Neck and kidney samples did not contain any Arsenic. Thus it can be concluded that the lead concentration in meat and edible organ samples collected from all the metropolitans exceeded the MRL values and is an indication of contamination. Appropriate precautions are warranted to minimize the heavy metal consumption contamination especially of Pb and As.

Influence of Lactobacillus buchneri on soybean curd residue co-conversion by black soldier fly larvae (Hermetia illucens) for food and feedstock production

Black soldier fly larvae (BSFL), Hermetia illucens (Diptera: Stratiomyidae) can reduce environmental pollution and convert organic wastes into biomass that is rich in protein and fat. The influence of the nutritional characteristics of organic waste on BSFL characteristics relevant for food and feed safety remains poorly understood. To evaluate the conversion of soybean curd residues (SCR) into high-quality animal-derived proteins and fats for human and livestock consumption, this study assessed the co-conversion efficacy, nutrient composition, safety, and anti-nutritional factor concentrations in BSFL after the development on SCR with Lactobacillus buchneri (L3-9). SCR was pretreated with L. buchneri (108 cfu/ml), and then BSFL was employed for conversion. BSFL fed with SCR and L. buchneri had a significantly higher dry mass reduction (55.7 ± 0.9%), bioconversion rate (6.9 ± 0.3%), crude protein content (55.3 ± 0.6%), and fat content (30.0 ± 0.6%) than SCR (49.0 ± 0.7%, 5.0 ± 0.3%, 52.8 ± 0.3%, and 26.1 ± 0.8%, respectively) and artificial feed (43.9 ± 0.8%, 3.9 ± 0.1%, 50.3 ± 0.4%, and 24.3 ± 0.4%, respectively). However, the feed conversion ratio (8.0 ± 0.3), of BSFL fed with SCR and L. buchneri was lower than that of the BSFL fed with SCR (9.8 ± 0.1) and artificial feed (11.1 ± 0.5). In addition, BSFL had satisfactory concentrations of all essential amino acids and fatty acids required for human consumption as recommended by WHO/FAO/UNU. The heavy metals and anti-nutritional factor concentrations were within the safety intake levels for food and feedstock. Therefore, the addition of L. buchneri with BSFL on SCR did not only increase co-conversion performance but also enhanced the nutritional value of BSFL.