Criticism: The size of the particles in the ground feed can cause stomach inflammation.

Reply: We know that the particle size of the feed can cause stomach inflammation, which is why we made sure that the particle size was the same between the GM and non-GM diets.  In the paper, we state: “GM and non-GM corn were both ground using the same cleaned equipment, size screen and revolutions per minute to obtain the same particle size”.  Therefore the increase in severe stomach inflammation that was seen in the GM-fed pigs cannot be due to the particle size of the diet.  In fact, the results clearly show that the GM diet added to the background level of inflammation that was caused by particle size and anything else. That is, there were fewer GM-fed pigs in the mild to moderate range of stomach inflammation because the GM diet had pushed them into the severe inflammation category. 

Author: Dr Judy Carman and Howard Vlieger

Criticism: The increase in uterus size was due to mycotoxins in the feed.

Reply: We know that mycotoxins can be a problem in corn, which is why we measured them in the pig diets. From the same section of the paper: “Mycotoxin analyses (Midwest Laboratories Inc, Omaha, Nebraska, US) showed 2.08 ppb total aflatoxins and 3.0 ppm total fumonisins in a pooled sample of the GM feed and no aflatoxins and 1.2 ppm total fumonisins in a pooled sample of the non-GM feed. No other mycotoxins were detected. These levels are well below the USA and EU limits for mycotoxins in pig feed. In addition, according to common industry practice, a mycotoxin binding agent (200 mesh bentonite clay) was added to the diets of young pigs (Table 1)”.

Therefore, not only are the levels of mycotoxins in the feed below the official level of concern as stated by the US government and the European Union, but a mycotoxin binding agent was also added to further reduce the ability of any mycotoxins to have any effect on the pigs.  Furthermore, the mycotoxins that can cause uterine swelling also tend to cause ovarian swelling. The results clearly show that there was no difference in the weight of the ovaries between the GM-fed and the non-GM-fed groups of pigs.

Therefore, the small amount of mycotoxins in the diet cannot have caused the increase in the weight of the uterus of the pigs on the GM diet.

Criticism: The researchers did not use isogenic corn and soy lines in their non-GM diet.

Reply: Crops that are isogenic to a GM plant have exactly the same genetics as the GM plant, except for the GM DNA that was inserted in the plant.  That is, the isogenic line is the exact plant variety that a GM crop was made from.

It is important to note that it is often very hard for researchers who are not aligned with the GM industry to be able to obtain isogenic plants or seeds.  These plants and seeds are usually not available to buy “over the counter”.  Instead, researchers often need to ask GM crop companies for them.  And the GM companies can and do choose who they give material to.

Furthermore, the main variety of corn used in the study was a triple-stacked variety, for which there is no single parental line, so it is not possible to have an parental, isogenic line for this corn variety.

As stated in the Materials and Methods section of the paper, the GM crops used in this experiment have been analysed and found by numerous regulators around the world to be substantially equivalent to non-GM crops.  Hence, these regulators have determined that GM crops have the same protein, lipid, amino acid profile, mineral and vitamin content as their non-GM crop equivalents.  Therefore, they have determined that there is no genotypical variation between the GM and non-GM varieties used in this study that could influence the outcomes measured in this study.