DNA tests, horse meat, Richard III and BBC Radio Leicester Drive Time

DNA and Farm Animals

DNA and Farm Animals

DNA test­ing is an import­ant part of our life now — as we have seen with prov­ing that a skel­eton in Leicester comes from the body of the last Plantagenet King Richard III, and not a medi­aeval Monk, or with the implic­a­tions of find­ing horse meat in a lot of beef products. I’ve just done an inter­view with Ben Jackson on BBC Radio Leicester about track­ing the proven­ance of our food. Here are my notes and some com­ments about the things dis­cussed at the live inter­view by Ben Jackson. It will be avail­able for the next week at http://​www​.bbc​.co​.uk/​p​r​o​g​r​a​m​m​e​s​/​p​0​1​3​n​xz2 start­ing after the news and traffic roundup at about 17.15, 2hr15min from the start.

There is a very wel­come move towards trace­ab­il­ity of our food from farm to fork — that’s what why there are ever more com­plex codes stamped on every food item you buy. But the trace­ab­il­ity relies on a paper trail, and where there is money to be made by passing off some­thing cheaper as some­thing more expens­ive, some­body is going to try to falsify the doc­u­ments — fraud­u­lent labelling of inferior products. So that is where test­ing comes in: a retailer, or in the horse­meat case it seems even the man­u­fac­tur­ers, can check that some parts of the paper trail are cor­rect. For those read­ing this blog out­side the UK and Ireland, at the end of last year and pub­lished in January, a high pro­por­tion of horse­meat was found in beef­bur­gers (that’s English for ham­burgers inter­na­tion­ally) on sale in Ireland, by the Food Standards Agency of Ireland, and the same man­u­fac­tur­ing plants were sup­ply­ing sim­ilar product to many UK shops. Not sur­pris­ingly, nobody had really tested beef products for horse, horse­meat almost never being eaten in the UK. But now the test are being done, even after the ori­gin­ally sus­pect products were pulled from the shelf, both con­tam­in­a­tion of beef with pork, and out­right fraud of selling horse as beef in pro­cessed foods, has come to light in many products still on sale. Now the UK Food Standards Agency has star­ted test­ing on a lar­ger scale, the latest news this week is a ‘beef’ lasagne where over 60% of the meat is horse. (I’m afraid the true cyn­ics amongst us are sur­prised that there was indeed meat in such products; per­son­ally I would prefer a more botan­ical dish!)

The Radio Leicester inter­view was played in with the Prime Minister talk­ing at a press con­fer­ence this morn­ing, “It’s import­ant to say there’s no reason to believe any frozen food cur­rently on sale is unsafe or a danger to health. It’s not about food safety – it’s about proper food labelling and about con­fid­ence in retail­ers”. “Economical with the truth”, in the UK at least, has become a polite expres­sion, as used in Parliament, for accus­ing someone of telling an out­right lie. So I’m not quite sure how I say that our Prime Minister was being eco­nom­ical with the truth, but in the most lit­eral sense.  There are excep­tion­ally rig­or­ous rules about every aspect of treat­ment of our food anim­als from birth, through death and onwards to pro­cessing for food. Most people are entirely unaware of the huge record­ing, licens­ing and mon­it­or­ing over­heads that are there for keep­ing farm anim­als: for some spe­cies, the paper­work needed for mov­ing them in a van from one field to another is the longest part of the task, while every drug is recor­ded, their diet strictly defined, and both wel­fare and health mon­itored and recor­ded. (As a friend said to me when his wife had to wait 10 weeks for a hos­pital appoint­ment, he’d be in jail if his lame cow had to wait two weeks to see the vet.) While these rules are oner­ous, the Prime Minister should know that they are in place for two reas­ons: food safety and animal wel­fare. If the paper trail in the sup­ply chain is so com­prom­ised that there is no proper record even of the spe­cies in our food, it is almost cer­tain that the safety of the food is in jeop­ardy, and will not meet any­thing like the stand­ards of farm­ing or of pro­cessing that we have come to expect.

Fortunately, it seems people aren’t poisoned or aller­gic to horse­meat, but most horses are treated at some point in their life and have a residue of an anti-inflammatory paink­iller, ‘bute’, or phenyl­butazone which is not safe enough for human use. Perhaps the worst recent food con­tam­in­a­tion in the last dec­ade was addi­tion of melamine powder, from a plastic which includes nitro­gen in its molecules, to milk powder. Tests at that time could not sep­ar­ate melamine from pro­tein, and about 300,000 chil­dren in China were given milk with melamine to make it look like high-protein milk.

DNA is a remark­ably stable molecule, and is present in all the foods we eat that is made up of cells. Each cell has hun­dreds of mil­lions of four DNA let­ters (A, T, C and G) in a par­tic­u­lar sequence, and in that sequence of four let­ters (bases) in the DNA, there are char­ac­ter­istic sig­na­tures of whichever animal or plant made the cells. There are sev­eral ways to see which organ­ism made the DNA depend­ing what is required. Many tests will only tell you what is there when you test for that par­tic­u­lar animal. That seems to be the case with the test­ing of pro­cessed food in Ireland and the UK until now: nobody was test­ing for horse. How far should you go in mak­ing tests? Rabbit, don­key … or  less pal­at­able products: mink or dog; or rare but per­haps cheap meat: river buf­falo, camel, elephant?

Now, most DNA tests will use a molecu­lar method called PCR to amp­lify very char­ac­ter­istic pieces of DNA from a test sample. If they amp­lify, then that animal was used in the product — and you can see the product eas­ily in the labor­at­ory. But this test will only say whether what you are test­ing for is there: you need to do a dif­fer­ent test for each spe­cies. The test will take typ­ic­ally 8 hours.

More spe­cific, but much more expens­ive is read­ing the DNA let­ters to see which spe­cies if comes from. In this test, again spe­cific pieces of DNA are amp­li­fied from the test sample (exactly the same as was done in Leicester with Richard III), and then they are sequenced, and the DNA code made up of the four let­ters is com­pared with ref­er­ence samples. Anybody can see these ref­er­ence DNA sequences over the inter­net — search at www​.ebi​.ac​.uk for example. This will tell you all the anim­als that are present in a sample. I saw one super­mar­ket com­pany repor­ted these tests will cost £400 or £500 per sample ($/€ 750): this is higher than my lab but what a well-documented res­ult would cost (my raw costs without labour or pay­ing for facil­it­ies would be £5 for DNA extrac­tion, £5 for amp­li­fic­a­tion, £10 for sep­ar­a­tion and puri­fic­a­tion, £50 for the clon­ing of the DNA and isol­a­tion, then say 20 sequence runs totalling £200 so a total of c. £300 per sample). Altogether, this will take some­thing like a week: this is accept­able for frozen food although expens­ive in terms of stor­age and stock cap­ital. For fresh food, a week wait­ing for a test would not be pos­sible. Sequencing DNA will identify all the spe­cies present in the sample, but not the pro­por­tion present with any accur­acy. For that, another quant­it­at­ive PCR meth­ods with spe­cific primers is needed.

Other tests are also pos­sible: each animal has char­ac­ter­istic pro­teins, and anti­bod­ies (made in other anim­als) can be used to test to ori­gin of the pro­teins in meat. Formerly, hybrid­iz­a­tion with radio­act­ive DNA probes was used: now my lab. does this to see how DNA is organ­ized in a spe­cies, but not to exam­ine the ori­gin of the DNA.

DNA test­ing today needs the most minute sample: less than the weight of a pin is ample. This sens­it­iv­ity might be valu­able for identi­fy­ing a crook from a drop of blood, or a King from a few frag­ments of bone mar­row, but it brings another prob­lem for food. A fact­ory will typ­ic­ally be hand­ling hun­dreds if not thou­sands of tons of food each week, so how do you obtain a ‘typ­ical’ sample? A frag­ment of meat will ori­gin­ate from one animal — but will cer­tainly not be an ‘aver­age’ of the whole pro­duc­tion of the fact­ory. For sampling grain arriv­ing from a truck off the com­bine, there are many elab­or­ate but accur­ate bulk sampling approaches (pic­tured) but how can it be done with meat in a fact­ory? Another prob­lem is con­tam­in­a­tion: if samples are not care­fully taken and stored, they can become mixed with other samples. Moreover, mod­ern DNA tests are so sens­it­ive that a stray hair in a sample, per­haps pulled from a pet, would eas­ily be detected.

Over the last dec­ades, food test­ing has been a grow­ing industry: food safety has been driv­ing the increase, but fol­lowed closely by iden­ti­fic­a­tion of food com­pos­i­tion, whether that is with respect to aller­gens, or mis­rep­res­ent­a­tion of ingredi­ents as with horse in beef lasagne or bur­gers. The test­ing of food — and feed — is mostly done by offi­cial feed and food con­trol labor­at­or­ies which in the UK are mostly des­ig­nated by the Food Standards Agency. As far as I know, there are none in Leicestershire.

International trade has always been import­ant for food — think of the spice routes of the middle ages. But now it is a global mar­ket — some products can’t be grown in the UK, in other cases, they are sur­plus in some coun­tries. Kidney and liver not typ­ic­ally eaten in US, or ducks feet in the UK, but high value else­where (I once sat next to the UK duck-foot export expert on a flight to China!). But the scale of food trans­port is increas­ing — we want cheap food, but would rather have a less pro­duct­ive nat­ural land­scape around us, and want the same food year-round, so hence we are import­ing and trans­port­ing on an unpre­ced­en­ted scale. In the horse­meat case, the retail­ers pass the blame to the man­u­fac­tur­ers, who pass it to their sup­pli­ers. What is not­able to me is just how diverse and dis­tant these sup­pli­ers, who seem to have had the tampered doc­u­ment­a­tion, are from the pro­du­cers. My labor­at­ory in Leicester works closely with the research­ers at Teagasc - The Irish Agriculture and Food Development Authority, on the genet­ics of grass crops, a mult­i­bil­lion euro industry used to feed anim­als. It is clear from my in-box and Twitter traffic the poten­tial dev­ast­a­tion of the Irish cattle industry, up to now a byword for qual­ity and pur­ity, by the mal­prac­tices revealed by the DNA tests.

My lab and the University of Leicester does not do ‘food test­ing’ on a com­mer­cial scale, but we develop the sci­ence that is under­pin­ning the tests that are applied to food. This work is also import­ant for under­stand­ing the genetic and evol­u­tion­ary rela­tion­ships between food spe­cies — both anim­als and plants. We want to char­ac­ter­ize their nearest wild rel­at­ives, trace the genetic dif­fer­ences with mod­ern spe­cies, and see how new breeds of vari­et­ies are developed which are dis­ease res­ist­ant and pro­duct­ive. My research group works with both plants and anim­als. For example, for a num­ber of years we worked with the rela­tion­ships of all anim­als in the bovid group. This means we developed what could be used as DNA tests for dif­fer­ent anim­als such as river buf­falo (pw and user both ‘vis­itor’; a close rel­at­ive of cows), or the many deer spe­cies.

I think these para­graphs covered most of the areas I wanted to dis­cuss: the main point was to say DNA test­ing was now import­ant to veri­fy­ing the paper-trail show­ing the ori­gin of our food. We should be wor­ried about the level of deceit and fraud that has been revealed in the last two months; it looks as though it has not had a food safety impact but cer­tainly test­ing must be increased so we can be sure we buy what we want to eat.



Editor Pat Heslop-Harrison. ORCID 0000-0002-3105-2167

Pat Heslop-Harrison is Professor of Molecular Cytogenetics and Cell Biology at the University of Leicester. He is also Chief Editor of Annals of Botany.

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