Substances In Animal Feed Research Articles

Pemanfaatan Kapang Pelapuk Kayu (KPK) Indigenous Mycelioptora thermophilia KLUM1 Untuk Pengolahan Limbah Rumput Taman Sebagai Pakan Ternak

Axonopus compressus as garden waste has the potential to become forage for livestock if it is processed by reducing its lignin content. Lignin is an anti-nutritional substance in animal feed whose presence can reduce the digestibility of feed nutrients. Mycelioptora thermophilia KLUM1 produces ligninase which can degrade lignin. The purpose of this study were to determine the effect of fermentation time and the number of spores of the Mycelioptora thermophilia KLUM1 on the levels of lignin, crude fat, and crude protein of Axonopus compressus. This research is a laboratory experimental study using a Completely Randomized Design (CRD) method, the first factor is fermentation time (14, and 21 days) and the second factor is the number of spores (1,72 x 107 , 4,29 x 107 , and 8,59 x 107 cells). The results showed that the best conditions for the levels of lignin and crude fat in this study were 8.59 x 107 cells for 21 days with a lignin content of 9.98% ± 0.23 and crude fat content of 3.43% ± 0 .04, while the best condition for crude protein content was 1.72 x 107 cells for 14 days of 11.64% ± 0.18.

New Eco-Sustainable Feed in Aquaculture: Influence of Insect-Based Diets on the Content of Potentially Toxic Elements in the Experimental Model Zebrafish (Danio rerio).

According to the concept of circular economy, insects represent good candidates as aquafeed ingredients. Nevertheless, there are some potential chemical risks linked with insect consumption. In this study, we reared the teleost Danio rerio, used as an experimental model, with five experimental diets characterized by increasing levels (0%, 25%, 50%, 75%, and 100%) of full-fat Hermetia illucens (Hi) prepupae, substituting for fish meal (FM) and fish oil (FO). We investigated the presence of potentially toxic elements (PTEs) Cd, Pb, Ni, As, and Hg in larval (20 days), juvenile (2 months), and adult (6 months) fish. Quantitative determinations of Cd, Pb, Ni, and As were made with an atomic absorption spectrometer; the total mercury content was determined by a direct mercury analyzer. The substitution of FM and FO with Hermetia illucens meal led to a reduction in the content of some PTEs, such as Pb, As, and Ni, in fishfeed, leading to concentrations below the legal limit of undesirable substances in animal feed. By increasing the Hi meal dietary content, we observed in the Danio rerio specimens an increase in Cd, Pb, and Ni content and a reduction in As content for all life stages. Moreover, a general increase in the content of Cd, Pb, Hg, and Ni from larvae to juvenile was measured, while the shift of Danio rerio from the juvenile to the adult stage involved a significant increase in the content of Pb, Hg, and Ni. Larvae had a reduced ability to bioaccumulate metal(loid)s compared to juveniles and adults. In conclusion, the content of PTEs in Danio rerio is influenced both by the type of diet administered and by the life stage of the animal itself. This research demonstrates the possibility of using Hi prepupae as an aquafeed ingredient without exposing fish to a chemical risk and, in perspective, allows applying these eco-sustainable diets for the breeding of edible fish species, without endangering human health.

The use and control of antimicrobial substances in animal feed – EU regulations and the risks related to their presence

Animal feeds are routinely subject to contamination from diverse sources, including environmental pollution, activities of microbes, and veterinary drug residues. Contamination of feed with chemical substances such as coccidiostats or antibiotics can occur at the stage of production, transport and storage, and their presence may have a negative impact on the health of animals consuming feed contaminated with certain chemicals. This study presents the legal requirements for the production of feed, the presence of antimicrobial substances in feed, and the problem of contamination of feed with antibacterial substances as well as the possible transfer of these compounds to the animal tissues and the natural environment.

A Chemically Safe Way to Produce Insect Biomass for Possible Application in Feed and Food Production.

Black soldier fly (Hermetia illucens, HI, Diptera, Stratiomydae) has great potential as a food and feed ingredient in the European Union (EU). The production of insects as livestock feed or as food ingredients requires strict monitoring of the content of potentially toxic elements (PTEs) in the growth substrate, to meet the security requirements. This study aims to investigate the presence of PTEs, like cadmium, lead, mercury, arsenic, and nickel, in HI prepupae and in their growth substrates based on coffee roasting by-product and microalgae Schizochytrium sp. and Isochrysis sp. Analyses were carried out via graphite furnace atomic absorption spectrophotometry for Cd, Pb, Ni, and As, and via Direct Mercury Analyzer for Hg. All element concentrations found in growth substrates were below the legal limit of undesirable substances in animal feed (2002/32/EC). Elements concentrations in HI prepupae were in the range (mg kg−1 wet weight) of 0.072 to 0.084 for Cd, 0.018 to 0.026 for Pb, 0.010 to 0.032 for Hg, 0.036 to 0.047 for As, and 0.18 to 0.76 for Ni. Even if HI prepupae accumulated Cd, Pb, and Hg, our results indicated that the risk of exposure to PTEs from HI prepupae consumption is relatively low and in compliance with EU regulations.

Influence of Feeding Substrates on the Presence of Toxic Metals (Cd, Pb, Ni, As, Hg) in Larvae of Tenebrio molitor: Risk Assessment for Human Consumption.

Larvae of Tenebrio molitor L. (Coleoptera: Tenebrionidae) are particularly suitable as novel food for the human consumption; nevertheless, there are some potential safety risks linked with insect consumption. In this study we investigated the presence of Cd, Pb, Ni, As, Hg in new feeding substrates coming from solid residues generated by olive fruits processing, called olive-pomace, and their influence on the metal content in larvae of T. molitor. Morover, bioaccumulation factor and the mercury-selenium balance were evaluated. Analyses were carried out via graphite furnace atomic absorption spectrophotometry for Cd, Pb, Ni, As and Se, and via Direct Mercury Analyzer for Hg. All metal concentrations found in feeding substrates were below the legal limit of undesirable substances in animal feed (2002/32/EC). Concentrations in larvae were in the range (mg kg−1 wet weight): Cd 0.008–0.016, Pb 0.063–0.079, Ni 0.03–0.63, As 0.021–0.023, Hg 0.12 × 10−3–0.49 × 10−3, and Se 0.057–0.085. Statistically significant correlation between metal content in feeding substrates and in larvae was evidenced only for Hg, which bioaccumulates. Se protects from mercury toxicity, with a Selenium Health Benefit Value (HVBSe) of > 0. Overall, our results indicate that the risk of exposure to metals from consumption of mealworm larvae is relatively low and in compliance with European Union regulations.

Nitrite: Review of existing and new physiological data in ruminants

Nitrite is regulated as an undesirable substance in animal feed. “Products and by-products from sugar beet and sugarcane” are currently exempted from maximum limits. Technological work by the European sugar producers showed that the levels of nitrite in feed materials from sugar plant processing is variable without allowing a stringent control at the full-scale factory process. The German Sugar Association (VdZ) reviewed the physiological-toxicological data base on nitrite in ruminants considered by EFSA (2009): The established toxicological endpoint of nitrite is oxidized hemoglobin (methemoglobin) that leads to a lack in oxygen supply. The review revealed that the NOAEL (No Observed Adverse Effect Level) of 3.3 mg nitrite/kg bw/day in ruminants is based on a 1940 study with 990 mg nitrate/kg bw in cattle in which nitrite is not mentioned. As auxiliary, a nitrite dose of 99 mg/kg bw was imputed, nitrite considered as being 10 times more toxic, and an uncertainty factor of 3 applied. Published physiological data, however, suggest that such a nitrate dose would be associated with a much higher nitrite exposure and support a lower toxicity of nitrite. To substantiate this assumption, cannulated cows received 7.5 mg nitrite/kg bw/day over a period of 7 days. After dosage, the expected transient increase of nitrite in ruminal fluid was observed that disappeared 1.5 h after dosage. No relevant increase in methemoglobin was observed. From this study, it can be concluded, that repeated feeding of 7.5 mg nitrite/kg bw to cows did not result in adverse effects. The dosage corresponded to 5.5 g nitrite intake per day and would cover the exposure from molasses with 500 mg nitrite/kg when the other feed contained 10 mg nitrite/kg. The data are supportive that nitrite is a normal metabolite in ruminants that does not require a regulation as contaminant in feed for ruminants.

Development and validation of multi-residue and multi-class method for antibacterial substances analysis in non-target feed by liquid chromatography – tandem mass spectrometry

ABSTRACTA confirmatory HPLC-MS/MS method for the determination of residues of 11 antibacterial substances from different therapeutic class (β-lactams, lincosamides, fluoroquinolones, macrolides, pleuromutilins and sulfonamides) in animal feeds has been developed. The sample preparation is based on extraction with 0.1% formic acid in acetonitrile. Separation of the analytes was performed on biphenyl column with a gradient of 0.1% formic acid in acetonitrile and 0.1% formic acid in Milli-Q water. The developed method was validated following the guidelines included in the European Union Commission Decision 2002/657/EC. Limits of detection ranging from 79.22 to 193.60 µg/kg; instrumental and analytical linearity coefficients were above 0.99 for matrix-match calibration; and relative recoveries ranging from 76.04% to 117.39%. Repeatability of the method was in the range of 2.41–19.76% (CV, %), whereas reproducibility ranged from 6.52 to 28.40% (CV %). The method shown to be efficient and precise for quantification of the 11 antibacterial substances in animal feed. The results demonstrate the feasibility of the method for routine use to monitor these substances in feed. The validated method was successfully applied to eight suspect feed samples collected from the Association of American Feed Control Officials (AFFCO) and feed manufactures from Galicia (Spain) in June and July 2017. Of these 8 non-target feeds, 5 were positive for the presence of tiamulin, tylosin and sulfadiazine.

Nitrite: Review of existing and new physiological data in ruminants

Nitrite is regulated as an undesirable substance in animal feed. “Products and by-products from sugar beet and sugarcane” are currently exempted from maximum limits. Technological work by the European sugar producers showed that the levels of nitrite in feed materials from sugar plant processing is variable without allowing a stringent control at the full-scale factory process. The German Sugar Association (VdZ) reviewed the physiological-toxicological data base on nitrite in ruminants considered by EFSA (2009): The established toxicological endpoint of nitrite is oxidized hemoglobin (methemoglobin) that leads to a lack in oxygen supply. The review revealed that the NOAEL (No Observed Adverse Effect Level) of 3.3 mg nitrite/kg bw/day in ruminants is based on a 1940 study with 990 mg nitrate/kg bw in cattle in which nitrite is not mentioned. As auxiliary, a nitrite dose of 99 mg/kg bw was imputed, nitrite considered as being 10 times more toxic, and an uncertainty factor of 3 applied. Published physiological data, however, suggest that such a nitrate dose would be associated with a much higher nitrite exposure and support a lower toxicity of nitrite. To substantiate this assumption, cannulated cows received 7.5 mg nitrite/kg bw/day over a period of 7 days. After dosage, the expected transient increase of nitrite in ruminal fluid was observed that disappeared 1.5 h after dosage. No relevant increase in methemoglobin was observed. From this study, it can be concluded, that repeated feeding of 7.5 mg nitrite/kg bw to cows did not result in adverse effects. The dosage corresponded to 5.5 g nitrite intake per day and would cover the exposure from molasses with 500 mg nitrite/kg when the other feed contained 10 mg nitrite/kg. The data are supportive that nitrite is a normal metabolite in ruminants that does not require a regulation as contaminant in feed for ruminants.

The use of ionic chromatography in determining the contamination of sugar by-products by nitrite and nitrate

In 2010, the Directive on undesirable substances in animal feed entered into force and for the first time was laid down a maximum limit for nitrite content in sugar industry feed materials such as molasses and beet pulp. Due to a lack of suitable analytical methods for nitrite determination, this study was developed with the aim to standardize a nitrite analytical method in by-products from sugar industry.In this study high performance anion exchange chromatography with conductometric detection was used for determining nitrite and nitrate content of sugar by-products included in feed material.The study confirms the usefulness of the applied ion chromatographic method for the evaluation of the content of nitrite and nitrate in sugar by-products.The results showed that in many samples of beet pulp and molasses the content of “undesirable substances for animal feed” was below 15mgkg−1 (expressed as sodium nitrate at 12% of moisture).

Outcome of the consultation with Member States and EFSA on the basic substance application for Saponaria officinalis L. roots for use in plant protection as acaricide and plant elicitor

EFSA Supporting PublicationsVolume 14, Issue 7 1263E Technical reportOpen Access Outcome of the consultation with Member States and EFSA on the basic substance application for Saponaria officinalis L. roots for use in plant protection as acaricide and plant elicitor European Food Safety Authority (EFSA), European Food Safety Authority (EFSA)Search for more papers by this author European Food Safety Authority (EFSA), European Food Safety Authority (EFSA)Search for more papers by this author First published: 17 July 2017 https://doi.org/10.2903/sp.efsa.2017.EN-1263 Requestor: European Commission Question number: EFSA-Q-2017-00237 AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat References EFSA (European Food Safety Authority), 2009. Compendium of botanicals that have been reported to contain toxic, addictive, psychotropic or other substances of concern on request of EFSA. EFSA Journal 2009; 7(9):281, 100 pp. doi:10.2903/j.efsa.2009.281. EFSA Panel on Contaminants, 2009. Scientific Opinion of the Panel on Contaminants in the Food Chain on a request from the European Commission on Saponins in Madhuca Longifolia L. as undesirable substances in animal feed. EFSA Journal 2009; 9(2):979, 36 pp. doi: 10.2903/j.efsa.2009.979 EFSA (European Food Safety Authority), 2010. Conclusion on the peer review of the pesticide risk assessment of the active substance fenugreek seed powder (FEN 560). EFSA Journal 2010; 8(3):1448; 50 pp. doi:10.2903/j.efsa.2010.1448. European Commission, 2012. Guidance document on botanical active substances used in plant protection products. SANCO/11470/2012– rev. 8. 20 March 2014. 28 pp. Garcia, D., Ramos, A. J., Sanchis, V. and Marín, S., 2013). Equisetum arvense hydro-alcoholic extract: phenolic composition and antifungal and antimycotoxigenic effect against Aspergillus flavus and Fusarium verticillioides in stored maize. J. Sci. Food Agric., 93: 2248– 2253. doi:10.1002/jsfa.6033 Volume14, Issue7July 20171263E ReferencesRelatedInformation

Presence of free gossypol in whole cottonseed.

The European Commission asked EFSA to assess information provided by the Spanish Ministry of Agriculture, Food and Environment, on the toxicity of free gossypol in relation to the use of whole cotton seed in feed for ruminants, in particular dairy cows, and, if necessary, to update the previous opinion of the EFSA Panel on Contaminants in the Food Chain (CONTAM) on gossypol as an undesirable substance in animal feed. Gossypol is a polyphenolic compound that exists in a racemic mixture of (+)‐gossypol and (‐)‐gossypol isomers. It occurs in free or (protein‐) bound forms in cottonseeds. The most commonly used cottonseeds in feed are from Upland and Pima varieties. The Pima variety is considered more toxic due to a higher content of the (‐)‐gossypol isomer. Upland whole cottonseeds (WCS) are fed with no further processing (after delinting); Pima varieties normally undergo further processing (grinding or cracking). It is claimed that WCS have a greater retention time in the rumen, which results in an increased detoxifying activity, compared to a shorter ruminal retention time, in the case of cracked cottonseed or cottonseed meal products. Increased erythrocyte fragility has been observed in cows given WCS Upland varieties at similar exposure levels as those resulting from an inclusion rate of 10% of WCS containing gossypol at 7,000 mg/kg in feed – the maximum permitted level of gossypol in WCS suggested by the Spanish Delegation. The information from the Spanish delegation does not differentiate between varieties in their suggestion for an increase in the maximum permitted content of free gossypol for WCS. As both Upland and Pima varieties are grown in the EU and are used for animal feed, both varieties of WCS should be considered. The CONTAM Panel considered it not necessary to update the previous opinion.

Verification for the presence of inhibitory substances in poultry meat after the consumption of the feed mixture supplemented with fermented feed

The European Union has an obligation to ensure that feed produced in the European Union is safe for animals and also humans by ensuring food of animal origin is safe and wholesome. An increasing demand for safe, wholesome and nutritious animal products has led to the search for alternative substances in animal feed. Fermented feed has gained a lot of popularity in many animal diets today. They meet the demand for animal nutrition due to the formation of target substances with the desired properties. As some of them are attracting attention as potential antimicrobial agents that inhibit the growth of certain microorganisms, and the products of animal origin are controlled for the presence of residues of inhibitory (antimicrobial) substances, the aim of this work was to verify the presence of inhibitory substances in poultry meat (muscle, heart, liver, kidneys of broiler chickens) after the consumption of the feed mixture with addition of fermented feed (wheat bran fermented with the strain Umbelopsis isabellina CCF 2412) in a dose of 10 % of the total amount of the feed. The detection of residues was performed by two approved microbiological screening methods, the screening test for the detection of antibiotic residues (STAR) and the Premi®Test. Both methods detected the positive results and pre-identified the presence of residues of the inhibitory substances not only in the meat of broiler chickens but also in the investigated fermented feed. Due to the antimicrobial potential of the fermented feed and the possible presence of the false-positive results, each positive result must be confirmed by a confirmatory analysis.

Arsenic distribution in soils and rye plants of a cropland located in an abandoned mining area

A mining impacted cropland was studied in order to assess its As pollution level and the derived environmental and health risks. Profile soil samples (0–50cm) and rye plant samples were collected at different distances (0–150m) from the near mine dump and analyzed for their As content and distribution. These cropland soils were sandy, acidic and poor in organic matter and Fe/Al oxides. The soil total As concentrations (38–177mgkg−1) and, especially, the soil soluble As concentrations (0.48–4.1mgkg−1) importantly exceeded their safe limits for agricultural use of soils. Moreover, the soil As contents more prone to be mobilized could rise up to 25–69% of total As levels as determined using (NH4)2SO4, NH4H2PO4 and (NH4)2C2O4·H2O as sequential extractants. Arsenic in rye plants was primarily distributed in roots (3.4–18.8mgkg−1), with restricted translocation to shoots (TF=0.05–0.26) and grains (TF=<0.02–0.14). The mechanism for this excluder behavior should be likely related to arsenate reduction to arsenite in roots, followed by its complexation with thiols, as suggested by the high arsenite level in rye roots (up to 95% of the total As content) and the negative correlation between thiol concentrations in rye roots and As concentrations in rye shoots (|R|=0.770; p<0.01). Accordingly, in spite of the high mobile and mobilizable As contents in soils, As concentrations in rye above-ground tissues comply with the European regulation on undesirable substances in animal feed. Likewise, rye grain As concentrations were below its maximum tolerable concentration in cereals established by international legislation.

Cover Picture: ChemBioEng Reviews 5/2015

AbstractFour Types of PhytasesPhytate is the major storage form of phosphorus in plant seed. It is an anti‐nutrient substance in animal feed due to the lack of digestive enzyme in monogastric animals. Although the phosphorus deficiency could be compensated by adding inorganic phosphorus, excessive phosphorus has caused environmental pollution. By using microbial phytases as animal feed additives, phytate can be hydrolyzed to liberate phosphate and both problems can be solved ingeniously. Nowadays, as one of the most important eco‐friendly enzyme products in global market, phytases have been studied extensively for the molecular mechanisms and for protein engineering to produce more powerful enzymes. Here the complex crystal structures of Escherichia coli histidine acid phosphatase (blue), Bacillus subtilis β‐propeller phytase (orange) and Selenomonas ruminantium protein tyrosine phosphatase‐like phytase (green) are shown, along with a model of soybean purple acid phosphatase (magenta).

Cover Picture: ChemBioEng Reviews 4/2015

AbstractFour Types of PhytasesPhytate is the major storage form of phosphorus in plant seed. It is an anti‐nutrient substance in animal feed due to the lack of digestive enzyme in monogastric animals. Although the phosphorus deficiency could be compensated by adding inorganic phosphorus, excessive phosphorus has caused environmental pollution. By using microbial phytases as animal feed additives, phytate can be hydrolyzed to liberate phosphate and both problems can be solved ingeniously. Nowadays, as one of the most important eco‐friendly enzyme products in global market, phytases have been studied extensively for the molecular mechanisms and for protein engineering to produce more powerful enzymes. Here the complex crystal structures of Escherichia coli histidine acid phosphatase (blue), Bacillus subtilis β‐propeller phytase (orange) and Selenomonas ruminantium protein tyrosine phosphatase‐like phytase (green) are shown, along with a model of soybean purple acid phosphatase (magenta).

Genetically Engineering Bacillus subtilis with a Heat-Resistant Arsenite Methyltransferase for Bioremediation of Arsenic-Contaminated Organic Waste.

Organic manures may contain high levels of arsenic (As) due to the use of As-containing growth-promoting substances in animal feed. To develop a bioremediation strategy to remove As from organic waste, Bacillus subtilis 168, a bacterial strain which can grow at high temperature but is unable to methylate and volatilize As, was genetically engineered to express the arsenite S-adenosylmethionine methyltransferase gene (CmarsM) from the thermophilic alga Cyanidioschyzon merolae. The genetically engineered B. subtilis 168 converted most of the inorganic As in the medium into dimethylarsenate and trimethylarsine oxide within 48 h and volatized substantial amounts of dimethylarsine and trimethylarsine. The rate of As methylation and volatilization increased with temperature from 37 to 50°C. When inoculated into an As-contaminated organic manure composted at 50°C, the modified strain significantly enhanced As volatilization. This study provides a proof of concept of using genetically engineered microorganisms for bioremediation of As-contaminated organic waste during composting.

Cover Picture: ChemBioEng Reviews 3/2015

AbstractFour Types of PhytasesPhytate is the major storage form of phosphorus in plant seed. It is an anti‐nutrient substance in animal feed due to the lack of digestive enzyme in monogastric animals. Although the phosphorus deficiency could be compensated by adding inorganic phosphorus, excessive phosphorus has caused environmental pollution. By using microbial phytases as animal feed additives, phytate can be hydrolyzed to liberate phosphate and both problems can be solved ingeniously. Nowadays, as one of the most important eco‐friendly enzyme products in global market, phytases have been studied extensively for the molecular mechanisms and for protein engineering to produce more powerful enzymes. Here the complex crystal structures of Escherichia coli histidine acid phosphatase (blue), Bacillus subtilis β‐propeller phytase (orange) and Selenomonas ruminantium protein tyrosine phosphatase‐like phytase (green) are shown, along with a model of soybean purple acid phosphatase (magenta).

Cover Picture: ChemBioEng Reviews 2/2015

AbstractFour Types of PhytasesPhytate is the major storage form of phosphorus in plant seed. It is an anti‐nutrient substance in animal feed due to the lack of digestive enzyme in monogastric animals. Although the phosphorus deficiency could be compensated by adding inorganic phosphorus, excessive phosphorus has caused environmental pollution. By using microbial phytases as animal feed additives, phytate can be hydrolyzed to liberate phosphate and both problems can be solved ingeniously. Nowadays, as one of the most important eco‐friendly enzyme products in global market, phytases have been studied extensively for the molecular mechanisms and for protein engineering to produce more powerful enzymes. Here the complex crystal structures of Escherichia coli histidine acid phosphatase (blue), Bacillus subtilis β‐propeller phytase (orange) and Selenomonas ruminantium protein tyrosine phosphatase‐like phytase (green) are shown, along with a model of soybean purple acid phosphatase (magenta).

Cover Picture: ChemBioEng Reviews 1/2015

AbstractFour Types of PhytasesPhytate is the major storage form of phosphorus in plant seed. It is an anti‐nutrient substance in animal feed due to the lack of digestive enzyme in monogastric animals. Although the phosphorus deficiency could be compensated by adding inorganic phosphorus, excessive phosphorus has caused environmental pollution. By using microbial phytases as animal feed additives, phytate can be hydrolyzed to liberate phosphate and both problems can be solved ingeniously. Nowadays, as one of the most important eco‐friendly enzyme products in global market, phytases have been studied extensively for the molecular mechanisms and for protein engineering to produce more powerful enzymes. Here the complex crystal structures of Escherichia coli histidine acid phosphatase (blue), Bacillus subtilis β‐propeller phytase (orange) and Selenomonas ruminantium protein tyrosine phosphatase‐like phytase (green) are shown, along with a model of soybean purple acid phosphatase (magenta).

Feed premix: a difficult matrix for the accurate determination of trace elements – the outcome of IMEP-114 and IMEP-36

This paper presents the outcome of two proficiency tests (IMEP-114/36) running in parallel, which focused on the determination of total As, Cd, Pb, Hg and Sn in feed premixes. Both exercises aimed to test the performance of laboratories measuring trace elements in feed, in compliance with Directive 2002/32/EC of the European Parliament and of the Council on undesirable substances in animal feed. IMEP-114 was run for the European Union National Reference Laboratories, while IMEP-36 was open to all food control laboratories that wished to participate. In total 80 laboratories from 37 countries registered to both proficiency tests, from which 75 laboratories reported results. The test material used in this exercise was commercially available feed premix, which was processed, bottled, labelled and dispatched to participants. The performance of the participating laboratories was similar in both proficiency tests and was very good in the case of total Cd and less satisfactory for total As and total Pb. For total Sn only one-third of the participants reported results, from which 33% performed satisfactorily. Thirty-four participants reported results for total Hg, although the expert laboratories stated that the mass fraction for that measurand was below the limit of detection of the method used. An evaluation of the reasons that could be at the basis of unsatisfactory results has been carried out and is presented here.