Stomach trouble disputed in GM hog feed study

The colour of a slaughtered hog’s stomach lining shouldn’t be taken as a sign that feed made with genetically-modified (GM) crops gave the live hog a belly ache, an Ontario veterinary professor warns.

Dr. Robert Friendship, a swine health management specialist at the University of Guelph’s Ontario Veterinary College, was responding last week to a paper by an Australian-led team studying a U.S. hog herd in this month’s issue of the Journal of Organic Systems.

The study, which involved 168 weanling hogs fed in a commercial barn in Iowa, alleged a higher rate (32 per cent) of “severe” stomach inflammation in a group fed a ration incorporating GM corn and soy, compared to 12 per cent of those fed a non-GM diet.

Friendship, on the blog of former Ontario Corn Producers Association vice-president Terry Daynard, wrote that it was incorrect for the researchers in the JOS report to conclude one group of hogs had more stomach inflammation than the other, “because the researchers did not examine stomach inflammation.”

Rather, he wrote, the team led by Australian biochemist Judy Carman “did a visual scoring of the colour of the lining of the stomach of pigs at the abattoir and misinterpreted redness to indicate evidence of inflammation. It does not.”

There is no relationship, Friendship said, between the colour of the stomach in a “dead, bled-out pig at a slaughter plant” and inflammation.

To diagnose inflammation, he said, the authors of the JOS paper should have included a veterinary pathologist on their team, taken tissue samples, prepared slides and looked for “evidence of inflammatory response, such as white blood cell infiltration and other changes.”

“Reaching puberty”

Friendship also critiqued the Carman study’s claim that uteri of GM-fed pigs were 25 per cent heavier than those of non-GM fed pigs.

The Carman paper, Friendship said, “did not admit the weaknesses of the study design and caution readers that there may be many reasons for a difference in uterine weight. Unfortunately, instead of presenting a fair discussion they made wild speculation about the weight difference such as the heavier weight might indicate cancer.”

Treatment, he said, was applied at the pen level in the Carman study while the statistical analysis was done at the individual animal level.

The Carman team, he said, did not suggest the heavier uterine weight “might be a result of some of the pigs in one pen of 42 pigs reaching puberty, which would be a reasonable possibility, or that there may be estrogen-like substances in the feed at low levels” produced by mycotoxins.

Grain Farmers of Ontario last week also ripped the Carman study, saying the JOS “is funded by anti-GM groups and is strongly biased.”

The organization said “numerous independent studies conducted over the past 15 years have found no difference between animals fed GM or non-GM diets.”

Seed biotech and ag chem firm Monsanto, writing last week on a company blog, also criticized the study for its affiliations, saying the study’s release was announced through GM Watch and Sustainable Pulse, “two advocacy organizations opposed to GM food.” Carman’s own website, Monsanto said, “is devoted to anti-GM food reports.”

The Carman study, the company said, is “likely more advocacy science, with the emphasis on the advocacy and not on the science.” — Network

Related story:
Scientists say new study shows pig health hurt by GM feed, June 12, 2013

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