Science in Society Archive

“Disappearing Rats and Dying Pigs”
Are GMOs to Blame?

Grim reports of dying pigs in China since 2006; are they linked to GM feed? Dr. Mae-Wan Ho

On 21 September 2010, the International Herald Leader (Chinese) carried a report from Xinhua news agency on the mysterious disappearance of rats from the fields and villages in the provinces of Shaanxi and Jilin, while farmers’ pigs were decreasing in number simultaneously as the sows were suffering miscarriages and still births. People blamed the new Xianyu 335 (XY335) corn that they have planted and used as feed for several years.

XY 335 is a hybrid corn owned by Pioneer, a subsidiary of DuPont. It was introduced into the market in 2004 with the formal approval of the Agriculture Ministry, and sales exploded in 2008-2009. XY335 was suspected to be a GMO (genetically modified organism), or a hybrid between a GM and non-GM variety.

Jin Wei, investigative journalist then working for the newspaper that belongs to Xinhua, had travelled to the villages to see for himself that the rats were indeed disappearing from the village and fields planted with XY 335, and more disturbingly, sows fed on the hybrid corn gave birth to far fewer (as well as dead and deformed) piglets than those of farmers who had not taken up the new hybrid corn. This was the start of a saga that Jin presented at the recent conference on GMOs and Food Safety International Forum held in Yunnan, China [1].

XY335 GM or not GM?

Jin had looked up the patent for PH4CV (the male parent), and although it is an inbred maize line, the patent is extremely broad, and covers any other inbred line derived from it, and the hybrids, and any transgenic plant derived from it. It states [2]:

“According to the invention, there is provided a novel inbred maize line, designated PH4CV. This invention thus relates to the seeds of inbred maize line PH4CV, to the plants of inbred maize line PH4CV, to plant parts of inbred maize line PH4CV, to methods for producing a maize plant produced by crossing the inbred maize line PH4CV with another maize plant, including a plant that is part of a synthetic or natural population, and to methods for producing a maize plant containing in its genetic material one or more transgenes and to the transgenic maize plants and plant parts produced by that method. This invention also relates to inbred maize lines and plant parts derived from inbred maize line PH4CV, to methods for producing other inbred maize lines derived from inbred maize line PH4CV and to the inbred maize lines and their parts derived by the use of those methods. This invention further relates to hybrid maize seeds, plants, and plant parts produced by crossing the inbred line PH4CV with another maize line.”

Could XY 335 be GM, or contain GM material? Jin thought so, possibly because he was already alerted to the deaths and deformities of animals on GM feed reported by farmers from other countries and in the scientific literature (see [3] Why GMOs Can Never be Safe, SiS 59). In fact, he had written a leader published 17 September 2010 in the International Herald Leader that was reprinted in a weekly magazine, Wenzhai Zhoubao. The story was picked up and widely reported in the media throughout China.

However, Pioneer was adamant that XY 335 is a hybrid between the inbred varieties: PH4CV (the male parent) and PH6WC (the female parent) neither of them GM [4].

Within a week, the Environment Ministry sent a team to Shaanxi and collected samples of XY335 for analysis. Three days later, the Agriculture Ministry sent out an announcement stating that the analysis did not reveal any GM component.

CaMV 35S promoter identified in XY335

But in November 2010, the Environment Ministry revealed that it found the cauliflower mosaic virus (CaMV) 35S promoter sequence in XY335, indicating that indeed it could be genetically modified. This was potentially explosive news. The finding was leaked to Jin, and he told a colleague at XinHua. The colleague interviewed the official at the Environment Ministry, and wrote to the then Premier of China Wen Jiabao.

As a result, in March 2011, the State Council Food Safety Committee held a series of 9 consultative meetings to solicit opinions from all sectors on XY335 and GMOs such as soybean and rice (which were also used in animal feed), while the Four Ministries once again investigated GMOs, focusing on XY335. In May 2011, the Nanking environment protection agency confirmed the presence of CaMV 35S promoter sequence in XY335.

On 30 June 2011, the Agriculture Ministry convened an advisory symposium on GMOs the purpose of which was to determine if XY335 is GM. The conclusion of the joint research of the committees was “no”.

At the symposium, Tong Pingya, a corn expert, asked the head of the educational department of the Agricultural Ministry in front of all the GMO experts, whether XY 335 is a GMO; he answered: “it is not.” Tong then requested that the test report be made public. But until now, the test report has not been released.

At the same time, Jin and his colleagues were carrying out their own further investigations; XY335 was causing more pig abortions in the provinces of Henan and Hebei.

They wrote up their report and sent itto Xinhua, and the agency forwarded it tothe central government. Several months later, on 26 September 2011, the Agriculture Ministry declared that XY335 was not GM; though they explained that “if the CaMV 35S promoter is found in the plants, maybe it is GM, but that needs to be confirmed.” 

On 9 September 2011, as the result of a petition from the people’s ministry of agriculture of Beijing, an official from the Agriculture Ministry admitted for the first time that the Environment Ministry had found the CaMV 35 S promoter in XY335. In a discussion between the petitioners and the official, the official said: “Yes, CaMV 35S is a gene promoter and promoters are naturally built into plants, and there are lots of promoters in any plant, one more promoter does not make a corn something else.”   Unfortunately, the official is quite mistaken (see later).

Back in March 2011, the Agriculture Ministry had already excluded XY335 from recommended varieties; on 8 February 2012, XY335 was again excluded from recommended varieties.  But by 2011, XY 335 had already become the second most popular corn seed in China, with over 40 million hectares under cultivation [5].

There were several more edicts and announcements throughout the year to reassure the public that XY335 was not GM. A national science journalists training course on GMOs was held on 23 August 2011, at which the head of science education on GM and safety in the Agriculture Ministry said [1]: “XY 335 is basically non-GM, even if it really affected the ecosystem, it has nothing to do with GM.”

Some organic farmers who have not planted XY335 or any GMOs are also sceptical about the sweeping claims made in Jin’s article. They point out that there are all kinds of additives in food and feed that could be toxic; and doubt that GMOs could be solely responsible. Lack of hygiene could also contribute to pigs dying.

Another factor is the meteoric rise of meat consumption in China, which made farmers not only use more corn to feed more pigs, but also soybean meal made from imported soybean.

Witnesses in the villages and on farms

The problem of dying pigs has not gone away. Only this year, there have been several reports on Microblog (Chinese version of Twitter) from Henan Province. One man writing from Zhengzhou, his home town, was told by farmers: “It is killing us. The sows ate 335 and don’t go into estrus, or their litter size goes down. Previously, the litter is 10 or more, after 335, it is 5 or 6. Now, no farmer with sows dares feed 335!” Another wrote: “My friend’s older sister rear pigs, and since I warned her against feeding with the GM corn, the 100 or so pigs are safe and well; their neighbour had not been warned; they bought two car loads of XY 335 and fed the pigs, the pigs all died within 2 months.” A third wrote: “I have planted XY335, it gives high yields and resists diseases, but chickens eating it don’t lay eggs; and sows don’t produce litters.”

It was farmers themselves who had observed that the animals appeared to be harmed when the pigs were fed XY335. The first instance was in Doumen village, YuanYang, Henan Province. Pigs were fed on 335, after a month or two, more than 10 sows failed to reach estrus. The remaining sows gave birth to piglets, but they were not healthy. A hundred pigs and piglets were lost the year before. As soon as they stopped feeding 335, the sows returned to normal.

A second observation was made by three farmers in Checheng village, Jiyuan prefecture, also in Henan. One farmer fed his pigs on 335 for one or two months, previously fertile sows mysteriously failed to come into heat, while others giving birth had far fewer piglets. Before, the litter was 15, but after 335, it was at most 10 and often only 2 or 3 (see photographs). There were also stillbirths, or piglets that died a month after birth. His two neighbours’ pigs, which were not fed on 335, remained as normal as ever.

Jin meanwhile had sent despatches from 13 townships and counties in Henan, Hebei and Shaanxi, reporting similar findings from farmers.

Jin stressed that the farmers did not know anything about GMOs, they made their discovery through practical experience. Nevertheless, after he and his team visited, one farmer from YuanYang carried out a full investigation on the effects of different feed. One group of pigs was fed on largely 335 maize, another group was fed an indigenous maize. The results were the same: as long as the pigs were fed 335, the sows miscarried or gave birth to dead piglets, and the few live births were quite sick and soon died. Are the observations of farmers not evidence? Jin asked.

Finally, scientist Jiang Gaoming of The Chinese Academy of Sciences carried out an experiment in Jiangjia village of Piyi county, Shangdong Province. Three groups of the same breed and age of chickens – each with 13 hens and one cock - were compared over a period of 263 days. The group fed XY335 laid 121 eggs, the group fed ordinary maize laid 349 eggs, and the group fed organic maize laid 449 eggs. The XY335-fed group produced only 34 % as many eggs as the group fed ordinary maize and 27 % as many eggs as the group fed organic maize. This confirmed what farmers have found. The results were published in the newspaper, Chinese Science.

Massive pig deaths nation-wide reached international media

In March 2013, more than 16 000 dead pigs were found in tributaries of the Huangpu River not far from Shanghai in eastern China. Simultaneously, scores of diseased pig carcases were found in Liuyang River miles away in Hunan Province, south-central China [6].

According to the National Bureau of Statistics, China sold 700 million pigs in the world market in 2012, about half of global pig production. The Chinese government’s way to decontaminate and dispose of disease carcasses is for farmers to bury them at least 1.5 metres deep or have them cremated, and then apply for compensation of 80 Juan (US$13) for each pig. In practice, however, dead pig carcasses are most often thrown into rivers or dumped elsewhere. A large number are sold on the black market and end up on people’s plates. The compensation is set far too low. A dead pig costs the farmer between 1 120 and

 1 400 Yuan.

A Chinese farm admitted to dumping dead pigs into the Huangpu River. The labels on the pig ears indicated Jiaxing city south of Shanghai in Zhejiang Province. The city government said a total of 70 000 pigs died from “crude raising techniques and extreme weather” at the beginning of the year [7]. A water sample was later found to contain a porcine circovirus – harmless to humans according to the World Health Organisation - which may have been responsible for the epidemic. But rumours are rife, with bird flu being suspected of having killed the pigs along with tens of thousands of ducks and swans and three human victims [8].

Since his report in 2010, Jin has received many letters from students, workers, farmers, including one from an expert in animal husbandry. They describe how, since 2006, China’s pig herds have been dying in large numbers, from miscarriages, spontaneous abortions, still births and from toxins that undermine the pig’s immune defence against infections. Officials have carried out investigations on the causes of death, but to no avail. The pigs have not stopped dying in large numbers. Apart from the introduction of XY335 since 2004, GM Roundup Ready soybean has been imported. China imports tens of million tons of soybeans every year, at least 80 % GM, from the US, Brazil, and Argentina. Soybean oil is extracted for human consumption, and the meal is fed to chickens and pigs [5].

The letter Jin received from the animal husbandry expert painted a frightening picture of epidemics spreading among pig herds in China:

 “In recent years, the pig herds over vast areas in our country are struck by disease. To be more specific, it started in the summer of 2006 in Jiangxi Province.  At the time, the pig herds were dying, suffering miscarriages and stillbirths on a large scale; the condition is commonly referred to as “high fever disease”.

“Several months later, the official story was: “highly pathogenic blue-ear disease”. The following year, inactivated and live vaccines were created against blue-ear disease, with far from ideal results. Until today, this problem is still extremely common. The general opinion is that since high fever disease, it is difficult to rear pigs. No one knows how to control the pigs’ disease.

“Apart from the official high fever blue-ear disease, another hypothesis in 2006 was mycotoxins from corn..….

“Until now, I cannot understand the reasons for pigs to succumb to the disease for so many years. The only concrete finding is that pig herds have reduced immunity to disease. The piglets are suffering from respiratory illnesses and their survival rate has dropped precipitously. Sows deliver stillbirths, or miscarry, or die, and this is happening all over the country: Jiangxi, Hubei, Hebei, Henan, Guangxi, Guangdong, Hunan, Sichuan, Chongqing, and so on…

There has been no reprieve from the pig illnesses since 2006…”

A closer look at XY335 and CaMV 35S promoter

There has been practically nothing known about XY335 apart from the information provided in the DuPont patent on PH4CV. A study published in 2011 by scientists at Henan Agricultural University characterized the proteins synthesized in the hybrid and its parental inbred varieties, PH4CV (the male parent) and PH6WC (the female parent) by 2-dimensional electrophoresis [9]. They found 560 protein spots in XY335, compared with 507 and 508 protein spots in PH6WC and PH4CV, respectively. In XY335, 81 % of protein spots exhibited non-additive expression:  288 were up-regulated compared to the parental varieties, while only 15 were down-regulated in comparison. They concluded that such non-additive gene expression might be the key factor responsible for the hybrid vigour of XY335. Notably, 13 significantly different protein spots between the hybrid and its parents were involved in metabolic pathway, protein folding, stress response, cytoskeleton and cell detoxification. There were over 50 extra proteins in the hybrid not present in either parent. The study provided no information as to why XY335 could be toxic.

If the presence of CaMV 35S promoter in XY335 can be confirmed, then the hybrid could indeed be a GMO, or at any rate, contain GM DNA. If so, it could be yet another example of the inherent toxicity of GMOs, now confirmed by farmers and scientists all over the world (see [3]). There are many potential causes of harm due to the inherently uncontrollable process of genetic modification, so that without detailed characterization, it is impossible to pinpoint the actual cause(s). However, the GM DNA itself could be harmful, and the CaMV 35S promoter is a prime example of a hazardous piece of GM DNA [10] (Hazardous Virus Gene Discovered in GM Crops after 20 Years, SiS 57).  It has a recombination hotspot, which means it can break loose and transfer to other genomes, thereby causing mutations; it is also an aggressive promoter that works in all species including animal and human cells, thereby causing inappropriate expression of genes some of which could result in cancer. Recent research suggests it may enhance the multiplication of disease-associated viruses including HIV (human immunodeficiency virus). In addition, its sequence overlaps with a virus gene (gene VI) that inhibits gene-silencing, a crucial host defence against viral infections. The last two characteristics of the CaMV 35S promoter could indeed compromise the immune system’s ability to defend against viral infections.

According to information provided by the Biosafety Clearing House database [11], the CaMV 35S promoter is in nearly all GMOs approved in China, either for environmental release such as MON-15985-7 cotton and MON-88913-8 cotton, or for processing, which include DuPont’s DAS-59122-7 corn and DAS-ø1507-1 corn,  and also MON-øø863-5 corn, MON-88ø17-3 corn, SYN-BTø11-1 corn, SYN-EV176-9 corn, ACS-ZMøø2-1/ACS-ZMøø3-2 corn, MON-ø4ø32-6 soybean, ACS-GMøø5-3 soybean, ACS-GHøø1-3 cotton, MON-øøø73-7 canola, ACS-BNøø8-2 canola ACS-BNøø7-1 canola, and ACS-BNø11-5 canola.

Roundup Ready soybean, a major animal feed in China, is already implicated in livestock death and infertility in the US and numerous other toxicities (see [12] Ban GMOs Now). RR soya too, contains an enhanced version of the CaMV 35S promoter [13]. A pathogen “new to science” thought to cause the death and infertility in livestock has been isolated by USDA scientist Don Huber and his colleagues from affected livestock and from RR soya, as described in his recent presentation to the GMOs and Food Safety International Forum in Beijing [14]. This was independently confirmed by scientists in the Chinese inspection and quarantine service who isolated it from imports of Roundup Ready soybean   (see [15] China's Consumers Reject GMOs, SiS 59).

Urgent need for investigations on the link to GMOs

There is an urgent need for China to investigate the mass deaths in pigs, in particular, the involvement of GMOs; and to make the findings public, before a colossal plague is unleashed that could spread around the world not only to pigs, but to other livestock, wild life and human populations.

Article first published 05/08/13


  1. Evidence of XY335 maize damaging farm animals. Presentation by Jin Wei at GMOs and Food Safety International Forum, 9-10 July 2013, Yunnan University of Finance Economics, Kunming, Yunnan.
  2. Inbred maize line PH4CV, US6897363 B1,
  3. Ho MW. Why GMOs can never be safe. Science in Society 59.
  4. “Dupont states: Xianyu 335 is not GM corn” (in Chinese), Dupont, 21 September 2010,
  5. “China ploughs a new corn furrow”, Peter Lee, Asia Times, 8 October 2011,
  6. “A plague of diseased pigs is poisoning China’s rivers, and maybe your dinner”, He Linlin, Caixinmedia, Worldcrunch, 23 April 2013,
  7. “Chinese farm says it dumped dead pigs in river”, Madison Park and Dayu Zhang, CNN, 14 March 2013,
  8. “Is new bird flue outbreak linked to 20 000 dead pigs? Three die in China as scientists isolate new strain of killer virus”, Daily Mail Reporter, 3 April 2012, Mailonline,
  9. Jin X-N, Fu Z-Y, Ding D, Liu Z-H, Li W-H and Tang J-H. Proteomic analysis of plumule in seed germination for an elite hybrid pio-neer 335 and its parental line in maize. Acta Agronomica Sinica 2011, 37, 1689-94.
  10. Ho MW. Hazardous virus gene discovered in GM crops after 20 years. Science in Society 57, 2-3, 2013.
  11. Biosafety clearing house, Convention on Biological Diversity,
  12. Ho MW and Sirinathsinghji E. Ban GMOs Now, Health and Environmental Hazards Especially in the Light of the New Genetics, I-SIS Report, 2013.
  13. Windels P, Taverniers I, Depicker A, Van Bockstaele E and De Loose M. Characterisation of the Roundup Ready soybean insert. Eur Food Res Technol 2001, 213, 107-112.
  14. Huber D. Failed promises; flawed science: Interactions of glyphosate and GMOs on soil, plant, animal human health. Presentation at GMOs and Food Safety International Forum, /Gloria Plaza Hotel, Beijing, China, 13 July 2013.
  15. Ho MW. China’s consumers reject GMOs. Science in Society 59.

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There are 4 comments on this article so far. Add your comment above.

James Cooley Comment left 6th August 2013 08:08:33
Are similar deaths and infertility being found in the US and other countries that use GMO feed? I haven't seen any reports, but perhaps they are being swept under the rug. The USDA should also investigate, but there is little chance with Monsanto in charge.

Mae-Wan Ho Comment left 7th August 2013 21:09:41
James Cooley, yes indeed, found in US, Denmark, Germany, and India among livestock, also in France, Austria, Russia, and Argentina in lab experiments. Please read Ban GMOs Now report.

Jon Singleton Comment left 8th August 2013 03:03:45
I've read the original Podevin and du Jardin article (damned by FSANZ and EFSA). I've also read the analysis from Jonathan Latham and Allison Wilson. None of these four authors suggest there is a species-barrier blocking this GMO plant virus from horizontally transferring to birds, animals and humans. FSANZ and EFSA are united in their shared "quasi-religious Monsanto delusion" (see FSANZ letter below)? So, from a science perspective, are CaMV 35S promoters and Gene VI within them active in birds, animals and humans? And are CaMV 35S promoters and Gene VI within them accelerants for cellular, bacterial and viral mutation? From: FSANZ no reply To: "" Sent: Thu, January 28, 2010 10:33:54 AM Subject: Letter to India's Environment Minister, Jairam Ramesh and Food Standards Aus [Sec: UNCLASSIFIED] Dear Mr Singleton, Thank you for your email dated January 25, 2010, raising concerns about the safety of genetically modified foods... Your email raises several issues which require clarification. Firstly, FSANZ carries out safety assessments on a case-by-case basis because this is the most appropriate method of assessment. Each genetic modification is unique, and as such, must be examined individually. The analogy with tobacco products is inappropriate, as in the case of cigarettes, the scientific evidence for harm is clear and credible. In the case of genetic modification of plants, there has been no credible science presented to establish harm from the ingestion of GM foods, and as such, there is no reason to assume an inherent danger in the process. Secondly, you raise concerns about the use of the cauliflower mosaic virus S35 promoter. Again, there is no credible evidence that crops containing this promoter undergo horizontal gene transfer at a rate any higher than exists in non-GM crops, or indeed that horizontal gene transfer has taken place. For reasons of biology, the presence of this or any promoter in a GM crop cannot result in the production of novel human viruses or bacteria. We trust you find this response helpful."

Todd Millions Comment left 30th August 2013 14:02:31
I find the modern ignorance in workers in the gm feild to be as astounding as the PR.For this -'sterile'hybrid seed-is actually average 2% viad. So it would seem too me that if the caulfower mosaic virus promoter is in any of the crops around these inbred hybrids,there is no reason some of the pollen or flowers could'nt pick it up and spread it-extensively,at a low level.Which with 300km/growing season documented spread,could be a very serious,non linear spread problem throughout whole crops and regions.What testing could and is being done to catch such-gene six spread out of research farms?