Determination of an appropriate heat treatment of animal waste using the ELISA technique: results of a validation study

Bridging legal requirements and analytical methods: a review of monitoring opportunities of animal proteins in feed

Availability and safety of food ranks among the basic requirements for human beings. The importance of the food producing sector, inclusive of feed manufacturing, demands a high level of regulation and control. This paper will present and discuss the relationships in the triangle of legislation, the background of hazards with a biological nature, and opportunities for monitoring methods, most notable for prion-based diseases as primary issue. The European Union legislation for prevention of prion-based diseases since 2000 is presented and discussed. The definitions and circumscriptions of groups of species will be analysed in the view biological classification and evolutionary relationships. The state of the art of monitoring methods is presented and discussed. Methods based on visual markers (microscopy), DNA-based methods (PCR), protein-based methods (ELISA, mass spectroscopy, proteomics), near infrared oriented methods and combinations thereof are being evaluated. It is argued that the use in legislation of non-homogeneous groups of species in a biological sense will hamper the optimal design of monitoring methods. Proper definitions are considered to act as bridges between legal demands and suitable analytical methods for effective monitoring. Definitions including specified groups of species instead of single species are more effective for monitoring in a range of cases. Besides the desire of precise circumscription of animal groups targeted by legislation, processed products need well defined definitions as well. Most notable examples are blood versus blood products, and hydrolysis of several types of material. The WISE principle for harmonising the design of legislation and of analytical methods is discussed. This principle includes the elements Witful (reasonable legal principles), Indicative (clear limits between prohibition and authorisation), Societal demands (public health, environment, economy), and Enforceable (presence of suited monitoring methods) in order to promote a balanced effort for reaching the desired level of safety in the food production chain.

Influences on the sensitivity of real-time PCR for the detection of bovine DNA in heat-sterilised feedstuffs

The present study evaluated two previously developed methods for amplification of bovine mtDNA segments of 109 and 271 base pairs (bp) by real-time polymerase chain reaction (PCR). Beef samples were sterilised experimentally at different temperatures (126 degrees C, 129 degrees C, 132 degrees C and 135 degrees C). These experimentally sterilised beef samples and nine commercial meat and bone meals (MBM) were mixed to a reference plant concentrate in strengths of 50%, 10%, 5%, and 1%. The results of the following PCR showed that the Bos-109 real-time PCR assay was able to detect all the experimental beef samples with exception of the mixtures of beef heated experimentally to 135 degrees C. In mixtures of industrial MBM bovine DNA were always found. Comparatively, the beef sterilised at 135 degrees C and 132 degrees C (and their respective mixtures) and the mixture containing 1% of beef sterilised at 129 degrees C were not detectable with the PCR assay amplifying a target of 271 bp. Using this PCR mixtures of industrial MBM were only weakly detected. The low concentrated mixtures of the extremely processed MBM-1 and MBM-2 even reported negative. These results indicate that the detectability of bovine DNA is strongly influenced by the degree of the thermal treatment. Only the PCR assay amplifying relatively short fragments of a multi-copy mitochondrial target was reliable for the detection of correctly heated MBM in mixed feed.

PCR identification of ruminant tissue in raw and heat-treated meat meals

To control the spread of bovine spongiform encephalopathy in cattle through contaminated animal feedstuffs, screening of feed products is essential. We designed five pairs of primers to identify specifically raw and heat-treated tissue from cattle, sheep, goat, deer, and ruminants in general. A forward common primer was designed based on a conserved DNA sequence in the mitochondrial 12S rRNA-tRNA(val)-16S rRNA gene, and reverse primers were designed to hybridize with a species-specific DNA sequence for each species considered. All primers were developed to create a specific PCR product small enough (less than 200 bp) to be suitable for heat-treated material. To evaluate the effect of heat treatment, a severe sterilization condition (133 degrees C at 300 kPa for 20 min) was chosen. Species-specific amplicons were obtained from all types of heat-treated meat meals. Analysis of laboratory-contaminated vegetable meals revealed that the detection limit of the assay was 0.05% for each species analyzed. This PCR-based analysis can be used as a routine method for detecting banned animal-derived ingredients in raw and heat-treated feedstuffs.

Development of immunoassay for detection of meat and bone meal in animal feed

An immunoassay system was developed for efficient detection of prohibited meat and bone meal (MBM) in animal feed. Monoclonal antibodies (MAbs) were raised against bovine smooth muscle autoclaved at 130 degrees C for 20 min. Among the 1,500 supernatants of hybridoma cells screened, MAbs 3E1, 1G3, and 3E10 were selected and characterized in this study. The first set of MAbs produced, 3E1 and 1G3, had stronger reactivity against MBM than against smooth muscle that was heat treated at 90 degrees C for 10 min. However, reactivity gradually increased against smooth muscle that was autoclaved at 130 degrees C for up to 1 h. The enzyme-linked immunosorbent assay for detection of MBM in animal feed was optimized with the MAb 3E10 because of its superior performance. MAb 3E10 diluted to 100-fold was used to differentiate bovine MBM from that of other species in ingredients used for commercial animal feeds and could detect down to 0.05% MBM mixed in animal feed.

Production of monoclonal antibody for the detection of meat and bone meal in animal feed

For the detection of prohibited meat and bone meal (MBM) in animal feed, monoclonal antibodies (MAbs) were raised against heat-stable h-caldesmon purified from bovine intestinal smooth muscle. The obtained hybridoma cells were screened against extracts of the bovine MBM and heat-treated smooth muscle, and MAb 5E12 was identified as having the best performance. Antibody 5E12 did not react with animal feed, milk product, plant proteins, and other ingredients used for commercial animal feed except for the gelatin. This antibody diluted to 100-fold was able to detect MBM mixed in animal feed at 0.05% in an ELISA, and it showed strong affinity toward bovine smooth muscle autoclaved at 130 degrees C. Therefore, this antibody can be used in the ELISA system for field testing of the presence of MBM in animal feed.

PCR detection of bovine mitochondrial DNA derived from meat and bone meal in feed

Because bovine meat and bone meal (MBM) is thought to be a major source of bovine spongiform encephalopathy, we developed a PCR-based method for detection of bovine MBM in animal feed. We isolated bone particles from feed containing bovine MBM using a separation technique based on specific gravity and then washed bone particles with sodium hypochlorite solution and an EDTA-proteinase K solution. The mitochondrial DNA was extracted from bone particles and amplified using PCR with cattle-specific primers. Bovine DNA was not detected in a milk replacer containing dried skim milk and dried whey, but bovine DNA was detected in the milk replacer that was mixed with bovine MBM. Other cattle-derived materials in feeds did not interfere with the selective detection of bovine MBM. This method allowed detection of bovine mitochondrial DNA in feed with 0.1% added bovine MBM. When the treatment with sodium hypochlorite was excluded, bovine DNA derived from MBM could not be distinguished from bovine DNA derived from other bovine materials. However, the exclusion of this treatment improved the detection limit of bovine MBM in feed. This method appears suitable for the selective detection of bovine MBM in feed.

Real-time PCR detection of ruminant DNA

To control the spread of bovine spongiform encephalopathy, several DNA methods have been described for the detection of the species origin of meat and bone meal. Most of these methods are based on the amplification of a mitochondrial DNA segment. We have developed a semiquantitative method based on real-time PCR for detection of ruminant DNA, targeting an 88-bp segment of the ruminant short interspersed nuclear element Bov-A2. This method is specific for ruminants and is able to detect as little as 10 fg of bovine DNA. Autoclaving decreased the amount of detectable DNA, but positive signals were observed in feeding stuff containing 10% bovine material if this had not been rendered in accordance with the regulations, i.e., heated at 134 degrees C for 3 instead of 20 min.

Identification of species-specific DNA in feedstuffs

Due to the menace of transmission of spongiform encephalopathies, feed components intended for ruminant nutrition must be checked for the presence of ruminant-derived materials. A sensitive method for the identification of bovine- and ovine- and also swine- and chicken-specific mitochondrial DNA sequences based on Polymerase Chain Reaction (PCR) has been developed. The specificity of the primers for PCR has been tested using samples of DNA of other vertebrate species, which may also be present in rendering plant products intended for feed manufacture. The method allows the detection in concentrate mixtures of 0.01% of the target species derived material. The identity of a sample containing 0.1% of bovine, ovine, swine, and chicken meat-and-bone meal has further been confirmed by sequencing.

A competitive polymerase chain reaction-based approach for the identification and semiquantification of mitochondrial DNA in differently heat-treated bovine meat and bone meal

The risk of bovine spongiform encephalopathy propagation was drastically reduced after the European Union (EU) Health Authorities adopted restrictions involving a ban on animal-derived proteins in the diet of farm animals. Currently, the EU's officially recommended method for controlling meat and bone meal (MBM) in animal feed is the microscopic method, which involves the identification of bone fragments on the basis of their morphological characteristics. Recently, we demonstrated that a polymerase chain reaction (PCR)-based assay can be used for the detection of taxon-specific DNA in MBM and animal feeds. To ensure the safe rendering of animal by-products, the EU Council requires that this material be treated at 133 degrees C at 300 kPa for 20 min. Here we investigate the relationship between DNA degradation, PCR amplification, and MBM heat treatment. With a competitive PCR-based approach, we compare the amplification efficiency of bovine mitochondrial DNA target sequences of different lengths in several heat-treated MBM samples. For our method, a synthetic competitive DNA is used as an internal control for both DNA extraction and PCR reaction. A correlation between an increase in treatment temperature and a reduction in the size of the target sequences suitable for amplification was observed, suggesting progressive DNA fragmentation due to the temperature. We show that short amplicons (147 bp) can be used to detect the presence of bovine mtDNA in MBM samples treated according to the current European regulations. The use of such a competitive approach to compare amplification efficiency levels of targets of different lengths might represent a useful tool for the determination of both the amount of MBM in animal feeds and its proper heat treatment.

PCR detection of DNAs of animal origin in feed by primers based on sequences of short and long interspersed repetitive elements

PCR primers for the detection of materials derived from ruminants, pigs, and chickens were newly designed on the basis of sequences of the Art2 short interspersed repetitive element (SINE), PRE-1 SINE, and CR1 long interspersed repetitive element (LINE), respectively. These primers amplified the SINE or LINE from total DNA extracted from the target animals and from test feed containing commercial meat and bone meal (MBM). With the primers, detection of Art2, PRE-1, or CR1 in test feed at concentrations of 0.01% MBM or less was possible. This method was suitable for the detection of microcontamination of feed by animal materials.

Real-time polymerase chain reaction detection of bovine DNA in meat and bone meal samples

We describe a real-time polymerase chain reaction (PCR) assay for the detection of bovine DNA extracted from meat and bone meal (MBM) samples. PCR primers were used to amplify a 271-bp region of the mitochondrial ATPase 8-ATPase 6 gene, and a fluorogenic probe (BOV1) labeled with a 5' FAM reporter and a 3' TAMRA quencher was designed to specifically detect bovine PCR product. The specificity of the BOV1 probe for the detection of the bovine PCR product was confirmed by Southern blot hybridization analysis of the probe with PCR products generated from ovine, porcine, and bovine genomic DNA extracted from blood and with PCR products generated from genomic DNA extracted from single-species laboratory scale rendered MBM samples. The specificity of the BOV1 probe was also evaluated in real-time PCR reactions including these genomic targets. Both methods demonstrated that the BOV1 probe was specific for the detection of bovine PCR product. The BOV1 probe had a detection limit of 0.0001% bovine material by Southern blot DNA probe hybridization analysis and a detection limit of 0.001% bovine material in the real-time PCR assay. Application of the real-time PCR assay to six industrial samples that had previously tested positive for the presence of bovine material with a conventional PCR assay yielded positive results with the real-time PCR assay for four samples.

Species-specific PCR for the identification of ovine, porcine and chicken species in meta and bone meal (MBM)

BSE, first identified in the UK in 1986 is thought to have arisen from feeding scrapie infected Meat and Bone Meal (MBM), produced under sub-optimal conditions, to cattle. For quality and safety reasons there is a requirement for a good analytical test for the surveillance of processed MBM. This study describes species-specific PCR assays for the identification of ovine, porcine and poultry species in MBM. A comparison between two distinct DNA extraction methods, i.e. the silicaguanidiumthiocyanate DNA isolation procedure and a commercial DNA extraction kit, is also presented. Application of this technology to species identification in industrial MBM was investigates as part of this study.

Identification of bovine-specific DNA in feedstuffs

Considering the menace of transmission of bovine spongiform encephalopathy, feed components intended for cattle nutrition must be checked for the presence of bovine-derived materials. We have been using a method based on polymerase chain reaction for the identification of bovine-specific mitochondrial DNA sequences for this purpose. The specificity of the primers for polymerase chain reaction has been tested using samples of DNA of other vertebrate species, which may also be present in rendering plant products. The method allows the detection in concentrate mixtures of 0.125% of bovine-derived material. Bovine DNA at concentrations corresponding to less than 0.5% of bovine-derived material was detected in 3 of the 30 samples of concentrate mixtures collected from distributors' stores all over the Czech Republic. All 44 samples of fish meal collected from the same sources were free of bovine-derived material.