An investigation into a traceability strategy for meat and bone meal

N. Shilton and S. Colgan
 
This project deals with the detection and identification of the composition of meat and bone meal (MBM) in animal feeds. Identification techniques used include DNA analysis, high performance liquid chromatography (HPLC) and simultaneous thermal analysis (STA). It was found that identification of DNA in some feedstuff samples was possible. Separation of soluble proteins extracted from the meat and bone meal using high performance liquid chromatography (HPLC) showed that there was potential for this technique to discriminate between feedstuffs of different origins. By using simultaneous thermal analysis (STA) it was possible to discriminate between sterilised and unsterilised MBM samples.
 

In November 1986 the disease Bovine Spongiform Encephalopathy (BSE) was identified in cattle in the United Kingdom (1), and it eventually reached epidemic proportions. The origin of the BSE epidemic has been identified to be the supplementary feeding of cattle with meat and bone meal (MBM) contaminated with a scrapie like agent (2, 3, 4). Meat and bone meal is produced by cooking discarded animal tissues from abattoirs, thereby enabling the melted fat to be collected (as tallow), leaving residual solids which are pulverised to produce MBM. This process is known as rendering. There is now a ban in place on the feeding of any feed containing MBM to ruminants. Therefore it would be advantageous to develop a test capable of verifying the presence or absence of MBM in a feed sample. At present the only way that this can be done is by microscopic analysis to identify bone fragments in the feed.

The purpose of this project is to develop techniques for the identification of MBM in animal feedstuffs.

 

Methodology
Preparation of single species meat and bone meal: Before it was possible to develop identification techniques for individual species it was necessary to source pure samples of individual species meat and bone meal. Due to the way material is processed it was not possible to source this meat and bone meal from any one rendering plant. Thus the first part of this project consisted of the manufacture of single species meat and bone meal in the laboratory. This preparation process has been described in detail by Colgan et al (5).

Techniques to identify the origin of MBM in a feed sample: In a wide ranging review of the processes that could be used in the species identification of MBM, the following techniques were identified; DNA based methods, high performance liquid chromatography (HPLC) and simultaneous thermal analysis (STA). The suitability of these techniques for species identification was then examined.

 
Main Findings
DNA based methods: Assays for the detection of bovine, ovine, porcine and poultry species were developed and tested. A detection limit of less than or equal to 3% was achieved for the bovine, ovine and porcine pure single species material. Testing of commercial samples showed that individual species could be identified in the meat bone meal in most cases. However a number of samples failed to give a response, which may indicate that the DNA associated with these samples was severely degraded (by overheating during rendering) and therefore not amenable to this type of analysis. Such difficulties have been encountered by previous researchers (6) and work in this area is ongoing.

High pressure liquid chromatography (HPLC): Protein and amino acids were extracted from meat and bone meal using an aqueous extraction procedure. Separation of the amino acids using HPLC was achieved from the single species meat and bone meal. Examination of the profiles by ratio analysis found 11 ratios that could be used to identify potential differences in the origins of samples (Fig. 1).

Fig. 1. Graphical illustration of 11 amino acid ratios for use in characterising the species origin of laboratory simulated MBM samples.

Simultaneous thermal analysis (STA): Simultaneous thermal analysis is not suitable for characterisation of species contained in a sample of MBM. However, it has shown application in confirming whether or not the MBM sample was sterilised according to EU regulations. This can be seen in Figure 2 by examination of heat flow profiles of a sterilised and unsterilised sample. There is a characteristic difference between the two plots, which could be used to determine the level of heat treatment in the sample.

Fig. 2. Heat flow response of samples of commercially sterilised and unsterilised meat and bone meal samples.

 
Acknowledgement
This research has been funded by grant aid under the Food Sub-Programme of the operational Programme for Industrial Development which is administered by the Irish Government's Department of Agriculture, Food and Rural Development and supported by national and EU funds.

 

References

  1. Wells GAH, Scott AC, Johnson CI, Gunning RF, Handcock RD, Jeffrey M, Dawson M, Bradley R, 1987. A novel progressive spongiform encephalopathy in cattle. Veterinary Record 121, 419-420.

  2. Fraser H, McConnell I, Wells GAH, Dawson M, 1988. Transmission of bovine spongiform encephalopathy to mice. Veterinary Record 123, 472.

  3. Dickinson AG, Taylor D, 1988. Proceedings of the Third World Congress on Sheep and Beef Cattle Breeding, 1. Paris, Versailles; INRA Publications. p. 553.

  4. Wilesmith JW, Wells GAH, Cranwell MP, Ryan JBM, 1988. Bovine spongiform encephalopathy: epidemiological studies. Veterinary Record 123, 638-644.

  5. Colgan S, Shilton N, McDonnell K, Ward S, 2000. The development of a laboratory-scale rendering (LSR) technique for the production of single species derived meat and bone meal, Fleischwirtschaft, In Press.