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

Preliminary Feed Sedimentation Step for the Sensitive and Specific Detection of Processed Animal Proteins by Mass Spectrometry-Based Proteomics

The circular economy is one of the main building blocks of the European Green Deal. In this context, the use of former foodstuffs containing ruminant gelatin was recently authorized in nonruminant feed. This minor modification makes it more challenging, if not impossible, to interpret the analytical results of the official control for animal proteins. The presence of ruminant DNA from authorized byproducts (i.e., milk and/or gelatin) may hide the use of prohibited byproducts. The objective of this work was to evaluate the use of sedimentation to increase the sensitivity and specificity of bovine-processed animal proteins (PAPs) detection by mass spectrometry-based proteomics. Both approaches (standard versus optimized method) were evaluated by UHPLC-MS/MS on various animal feeds and samples from an interlaboratory study. The optimized method was able to achieve the adulteration level below the level of 0.1% PAPs required by the European Commission. This approach presents a simple and economical solution to improve the method without the need for new equipment or expertise since it is already in place in the control laboratories.

Development of PCR primers for the detection of porcine DNA in feed using mtATP6 as the target sequence

In Japan, PCR identification of species-specific, animal group-specific and plant DNA is employed as part of the audit program to ensure compliance with the feed ban in place for the control of bovine spongiform encephalopathy (BSE). Since October 2001, animal proteins other than dairy proteins, egg proteins and gelatin have been prohibited to be used in feed for ruminants. Meat-and-bone meal (MBM) derived from poultry, pig and/or fish is allowed to be used in feed for poultry, pigs and fish. Porcine MBM is permitted in feed for domestic animals other than cattle since April 2005. Given the fact that pigs and cattle are the two major sources of MBM in Japan, the identification of porcine DNA with high specificity and sensitivity has become increasingly important to ensure that MBM products are free from ruminant materials. Two PCR primer sets (PPA8 and PPA6) were newly designed using mtATP8 and mtATP6 as the target sequences, with relatively short amplification sizes. PPA8 and PPA6 were able to specifically detect porcine DNA with the detection limits of 0.01% and 0.001% of porcine MBM in feed, respectively. PPA6 was superior to PPA8 in terms of detection of DNA damaged/fragmented during rendering procedures. The PCR method using these primer sets is registered as the official analytical method for feed in Japan.

Real-time PCR detection and identification of prohibited mammalian and avian material in animal feeds

A method for the detection and identification of "prohibited" mammalian or avian material in animal feed was developed and assessed through the analysis of DNA. A generic real-time PCR assay was designed to detect the presence of mammalian and avian mitochondrial DNA 16S rRNA genes in animal feed samples. Samples positive with this screening method were further investigated using identification assays to detect the 16S rRNA gene from bovine, ovine, porcine, and avian species and to determine whether the DNA originated from species whose material is prohibited from inclusion in farmed animal feed. An internal positive control was coamplified in the 16S real-time PCR assays to monitor PCR amplification efficiency and avoid potential false-negative results. Using vegetable-based feed standards spiked with meat and bone meal generated with a commercial rendering process, 0.1% meat and bone meal could be detected using the general and species-specific 16S assays. The species-specific assays had 100% specificity for the homologous target species. The 16S real-time PCR assays were evaluated alongside existing tests based on protein evaluation or microscopic examination for a wide range of commercial animal feed samples. In total, 111 (0.76%) of 14,678 samples examined contained prohibited material based on the results from at least one of these tests. However, most positive results did not represent noncompliance because they were associated with samples of pet food, which can legitimately contain material prohibited for use in food for farmed animals. The species-specific 16S assays confirmed the presence of prohibited material in 75% of the 111 samples, whereas the existing protein and microscope tests confirmed the presence of this material in 25 and 54% of the samples, respectively.

Developing PCR primers using a new computer program for detection of multiple animal-derived materials in feed

To reduce the risk of the bovine spongiform encephalopathy agent being recycled to cattle through animal feed, in October 2001 Japan introduced a feed ban prohibiting the use of animal proteins in feed. PCR identification of feed ingredients is part of the audit program to ensure the proper implementation of the feed ban. For efficient analysis, screening of feed products for materials from multiple species is essential. In our study, we developed a computer program GSPRIMER (http://www. famic.go.jp/ffis/feed/gsprimer/) that facilitates development of PCR primers specific to multiple species. The most important feature of GSPRIMER is its ability to estimate the specificity and homology of a potential primer in incremental steps from the 3' terminal. We analyzed all regions of mitochondrial DNA from the target and nontarget species using GSPRIMER. We designed species-specific primer sets for three animal species (sheep, goats, and swine) and group-specific primer sets for ruminants and animals susceptible to transmissible spongiform encephalopathy. The primers were efficiently screened by the PCR protocol using a mixture of mitochondrial DNA from nontarget species as a template. As a result, one primer set each for sheep and goats, two for swine, and three for a group of ruminant species were developed. The detection limit of one of the ruminant primer sets ranged from 0.05 to 0.01% bovine meat and bone meal and 0.1 pg of bovine DNA. We also successfully applied the primer set to 17 commercial feed samples that were known to be free from ruminant-derived materials. No false-positive results were found.

Real-time PCR for quantitative detection of bovine tissues in food and feed

A real-time PCR approach with the SYBR Green detection system has been developed for the quantitative detection of bovine tissues in food and feedstuffs. The method combines the use of bovine-specific primers, which amplify an 84-bp fragment of the mitochondrial 12S rRNA gene, and universal primers, which amplify a 140-bp fragment of the nuclear 18S rRNA gene from eukaryotic DNA. The 18S rRNA primers are used as endogenous controls for the total content of PCR-amplifiable DNA in the sample. The specificity of the primers was tested against 18 animal species, including mammals, birds, and fish, as well as 6 plant species. Analysis of experimental bovine tissues-oats mixtures demonstrated the suitability of the assay for the detection of bovine DNA in mixtures containing as low as 0.1% of bovine tissues. The performance of the method is not affected by severe heat treatment (up to 133 degrees C for 20 min at 300 kPa). The reported PCR assay could be very useful for detecting bovine-derived ingredients in raw and heat-treated food and feedstuffs.

Sandwich enzyme-linked immunosorbent assay for the detection of bovine blood in animal feed

The feeding of ruminant proteins to ruminants is prohibited in most countries because the practice is thought to be responsible for the spread of bovine spongiform encephalopathy. However, currently available methods to detect ruminant blood products in rendered feedstuffs are inadequate because they lack species specificity, tissue specificity, and are not based on a thermostable analyte. A sandwich enzyme-linked immunosorbent assay (ELISA) was developed for this study that provides reliable and sensitive (0.05-0.5% v/v) detection of bovine blood materials in animal feed. The new sandwich ELISA employs two previously developed monoclonal antibodies (MAbs), Bb6G12 as the capture antibody and biotinylated MAb Bb3D6 as the detecting antibody, and is bovine-specific and blood-specific. The assay is based on the detection of a 60 kDa thermostable protein in bovine blood and provides a useful regulatory tool for monitoring fraudulent labeling or contamination of bovine blood in both heat-processed feedstuffs and unprocessed raw materials.

KEYWORDS

Bovine; blood; monoclonal antibody; sandwich ELISA.

Technical note: Detection of cat, dog, and rat or mouse tissues in food and animal feed using species-specific polymerase chain reaction

A PCR method based on the nucleotide sequence variation in the 12S ribosomal RNA, mitochondrial gene has been developed for the specific and qualitative detection and identification of cat, dog, and rat or mouse tissue in food and feedstuffs. The primers designed generated specific fragments of 108, 101, and 96 bp in length for cat, dog, and rat or mouse tissues, respectively. Specificity of the primers was tested against 32 nontarget species including mammals, birds, fish, and plant species. This PCR method allowed detection of raw and heated cat, dog, and rat or mouse tissues in meat/oats mixtures even when the concentration of the target species was reduced to 0.1%. Furthermore, the performance of the method was not affected by prolonged heat-treatment (up to 133 degrees C for 20 min at 300 kPa), and consequently, it could be very useful to verify the origin of raw materials in food and feedstuffs submitted to denaturing technologies, for which other methods cannot be applied.

Application of quantitative real-time PCR in the detection of prion-protein gene species-specific DNA sequences in animal meals and feedstuffs

This study describes a method for quantitative and species-specific detection of animal DNA from different species (cattle, sheep, goat, swine, and chicken) in animal feed and feed ingredients, including fish meals. A quantitative real-time PCR approach was carried out to characterize species-specific sequences based on the amplification of prion-protein sequence. Prion-protein species-specific primers and TaqMan probes were designed, and amplification protocols were optimized in order to discriminate the different species with short PCR amplicons. The real-time quantitative PCR approach was also compared to conventional species-specific PCR assays. The real-time quantitative assay allowed the detection of 10 pg of ruminant, swine, and poultry DNA extracted from meat samples processed at 130 degrees C for 40 min, 200 kPa. The origin of analyzed animal meals was characterized by the quantitative estimation of ruminant, swine, and poultry DNA. The TaqMan assay was used to quantify ruminant DNA in feedstuffs with 0.1% of meat and bone meal. In conclusion, the proposed molecular approach allowed the detection of species-specific DNA in animal meals and feedstuffs.

Conventional and real-time PCR-based approaches for molecular detection and quantitation of bovine species material in edible gelatin

The majority of edible gelatin in Europe is derived from pigskin, but a significant portion is extracted from bovine tissue. Because of the bovine spongiform encephalopathy crisis, consumers might be concerned about the gelatin used in various products. To assure consumers of the quality and safety of edible gelatin, European Union directive 1999/724/EC described general guidelines for gelatin production, including requirements for documentary proof confirming that raw materials are from animals fit for human consumption. Analytical methods to confirm gelatin documentation or raw material animal species source in the finished product are lacking. In this study, several published species-specific PCR systems were evaluated as potential molecular methods for determining the origin of the raw material used in making gelatin. A recently validated bovine species-specific PCR primer set targeting the ATPase 8 subunit gene in bovine mitochondrial DNA was suitable for detection of bovine material in gelatin. This PCR primer set was optimized using conventional and real-time PCR approaches. An evaluation of these two PCR methods confirmed the high specificity for the adopted primer set in various gelatin matrices of known origin. The inclusion of bovine gelatin in pork or fish gelatin can be detected at 0.1 to 0.001%. These PCR assays are potential molecular detection tools that can be used to routinely detect bovine gelatin either alone or as an inclusion in gelatin made from other species.