NOTE: Monsanto has released a few comments on the Carman et al study, which showed increased severe stomach inflammation and uterine abnormality in pigs fed GM feed.
http://www.organic-systems.org/journal/81/8106.pdf

Carman and colleagues have answered the Monsanto critique (below). More answers to critics can be read at: gmojudycarman.org
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A specific reply to Monsanto
Dr Judy Carman and co-authors
GMOJudyCarman.org, 13 June 2013
http://gmojudycarman.org/a-specific-reply-to-monsanto/

Monsanto (M):  Some of the factors reported as different between the test and control groups appear to be in the normal range of observation for both.

Answer Summary:  Monsanto provided no proof for this statement.  Carman et al used adequate sample sizes, appropriate statistical tests and generated reliable findings.

Detailed Answer:  Monsanto do not back up their assertion with any data.  That is, they do not provide an officially-endorsed normal range for uterus weights for pigs, nor do they provide an officially-endorsed normal level of stomach inflammation in pigs.  In fact, they provide no data at all.

It is important to understand that Monsanto are saying that the level of severe stomach inflammation seen in pigs fed the GM diet is normal in piggeries – ie that it's normal for a third of pigs to experience severe stomach inflammation in piggeries.  This is a worrying animal welfare allegation about conditions in commercial piggeries and Monsanto needs to provide proof for their allegations.

It is also important to understand that the level of severe stomach inflammation in the GM-fed pigs was many times higher than in the non-GM fed pigs.  Overall, GM-fed pigs had 2.6 times the level of stomach inflammation, with female pigs experiencing 2.2 times the rate and male pigs experiencing 4 times the rate.  This is not “normal”.

M: The author’s speculation about differing uterine weights might be the result of pigs in estrus (heat) which would be complicated by the use of a pen design that had only 1 or 2 pens per treatment.

Answer Summary:  Randomisation and proximate housing ensured estrus was not a confounding factor.

Detailed Answer:  Two to six pens were actually used per dietary group, depending on the age of the pigs, not 1 or 2 as Monsanto says.

The weights of the uterus cannot be due to differing rates of estrus (heat) in the pigs, as pigs were thoroughly randomised before they began their diets. And then all the pens were placed very close to each other, so that pigs could touch snouts between pens.  So, if estrus in one pig stimulated estrus in another pig in this study, then all the pigs in both dietary groups should have been in estrus together. Which means that estrus cannot be causing the differences that were seen between the GM-fed and the non-GM-fed groups.

By Monsanto suggesting that the rate of estrus was different between the GM-fed and non-GM-fed pigs, then, because of the way the study was conducted, with everything except for the GM aspect of the diet “randomised out” from having an effect on the results, Monsanto is actually suggesting that the GM diet caused a difference in the rates of estrus in pigs. This is a hypothesis that is both interesting and worrying for health and should be followed-up.

M:  The results are due to poor animal husbandry practices, as shown by the fact that pigs died, even in the control group.

Answer Summary:  The pigs in both groups were treated equally, humanely and within commercial piggery standards. Any assumption otherwise would be contesting the standards of the U.S. government and should be directed as a complaint to U.S. legislators.

Detailed answer:  Pigs were housed under conditions that apply in commercial piggeries in the US.  If Monsanto is suggesting that these pigs were subjected to inhumanely poor conditions, then they are also suggesting more widely that pigs in commercial piggeries in the US are subjected to those conditions as well.  Pigs in commercial piggeries are housed in groups. They can and do get infectious diseases and there are indeed a number of infectious diseases that tend to occur in US commercial piggeries.  Furthermore, pigs fight, bite, and harass each other.  As a result, some pigs, particularly runts, can, and do, die.  Piggery owners expect some pigs to die and they factor this into their financial returns.  Indeed, if no pigs had died in this study, many US piggery owners would have found the results of the study rather incredible.

The number of pigs that died was essentially the same between the GM-fed and non-GM-fed pigs. All pigs that died underwent autopsies.  In all cases, death was found to be due to things such as infectious diseases, ie things that were piggery-related.  At no time did any pig handler or veterinarian note, or autopsy indicate, that there was anything treatment-related associated with any pig’s death, including intestinal or stomach problems.  Moreover, the number of deaths were the same between groups, which adds weight to the evidence that there was no treatment-related aspect to these deaths.

All pigs, regardless of dietary group, were fed and treated the same way by experienced pig handlers that were blinded as to the dietary group of the pig so that any differences between the two dietary groups can only reasonably be due to the effect of the GM component of the diet.