Do genetically modified crops affect animal reproduction? A review of the ongoing debate

Oral toxicity evaluation of genetically modified lactic acid bacteria in three generations of Sprague Dawley rats

Genetic modification has great advantages in improving performance of bacteria, but its oral safety has not been systematically evaluated. In this study, the toxicity including the reproductive toxicity of two genetically modified bacteria engineered using food-grade vectors on three generations of rats (F0, F1 and F2) were studied. Sprague Dawley rats were administrated by gavage with corresponding parent and genetically modified Lactobacillus plantarum and Lactobacillus delbrueckii at 2.5 × 10 ⁹ CFU every other day for 8 weeks. Results showed that the transgenic Lactobacillus had no significant toxicity to the body weight, food intake or blood biochemical parameters of three generations of rats. There was no significant effect on the reproductive parameters (gestational weight and pregnancy time) and related hormones (FSH, LH, estradiol, progesterone and testosterone) of the parent rats (F0 and F1). Consistently, their offsprings had no abnormal physical conditions including body weight, body length and anogenital distances. Moreover, their pups had normal body organ weight and reasonable abnormal sperm rate. Further analyses were conducted to evaluate SOD, MDA and GPX of the ovarium in the F1 and F2 female rats, which showed no malady phenotypes. In conclusion, transgenic Lactobacillus has no toxicity to the three generations of rats.

Food Safety Assessment of Commercial Genetically Modified Soybeans in Rats

Although the safety of commercial genetically modified (GM) soybeans has been well evaluated and GM soybeans are legally sold under government management, some consumers still have concerns about their safety. The objective of this study was to evaluate the safety of commercial GM soybeans sold in markets as a food source. In the present study, two commercial GM (GM-1 and -2) soybeans and one non-GM soybean were randomly purchased and subjected to a whole food toxicity assessment. Rats (SD), male and female, were divided into six groups (10/sex/group). Two dosages of 1 g/kg/day and 5 g/kg/day of soybeans were selected for the low- and high-dose groups. Rats were administered the soybeans via daily oral fed for 90 days. The results indicate that the body weight, organ weight, biochemistry, hematology, and urology showed no biologically adverse effects. At necropsy, no significant differences between organ weights were noted between the non-GM- and GM soybeans-treated groups. Moreover, no gross or histopathological lesions were observed in the high-dosage (5 g/kg/day) fed groups of the non-GM and GM soybean fed rats. In conclusion, this food safety assessment revealed that commercial GM soybeans are substantially equivalent to non-GM soybeans in rats.

Evaluation of the impact of transgenic maize BT799 on growth, development and reproductive function of Sprague-Dawley rats in three generations

BT799 was Bacillus thuringiensis-genetic modified (GM) maize, and Sprague-Dawley (SD) rats were treated with different diet formulations containing BT799 maize grain (33% and 66%) or its non-transgenic Zhengdan 958 (ZD958, 33% and 66%). The feeding lasted for 10 (P)/14 (F1 and F2) weeks. The reproductive capacity and pathological responses were detected in each generation of rats fed with BT799 and ZD958. During the growth and development of parental rats, each group showed the same trend in body weight gain and food intake, with a few fluctuations at individual time points. No statistically significant difference was observed in reproductive data (copulation index, fertility index, and live birth rate) of rats fed with transgenic maize compared with non-transgenic maize. We observed some apparent changes in reproductive data (sperm numbers and motility) and pathological responses (organ relative weights, hematological parameters, serum chemistry parameters, and sex hormone levels) among rats fed with BT799 maize grain. However, these differences were within the laboratory's historical normal range of control SD rats and not maize grain dose-dependent. These changes were not considered to be adverse or toxic. No significant difference in macroscopic or histological adverse effects was observed between rats consuming transgenic BT799 diet and non-transgenic diet. In conclusion, the long-term intake of BT799 maize was as safe as the corresponding non-transgenic maize for three-generation SD rats.

Evaluation of the effects of feeding glyphosate-tolerant soybeans (CP4 EPSPS) on the testis of male Sprague-Dawley rats

Glyphosate tolerant soybeans represent a large portion of soybeans grown and fed to farm animals around the world. Despite their widespread use for many years, some have raised questions regarding their safety because the soybeans were genetically modified. The CP4 EPSPS gene which imparts resistance to topical application of the herbicide glyphosate was introduced into soybeans. Application of glyphosate to soybean fields will reduce weed pressure and increase soybean yield. To assess their safety on the rat reproduction system, male Sprague Dawley rats were fed either glyphosate-tolerant (GM) soybean (40-3-2) or near-isogenic, non-GM (A5403) (control) soybean meal. The processed soybean meal was added to formulated rodent diets at 20% (w/w) and fed to rats for 90 days. Some rats from the control group were separately administered mitomycin C for 40 days and served as positive controls in the sperm abnormality test. Body weights and behavior were monitored daily, serum enzymes and histologic and EM appearance of the testis, and sperm morphology were also examined. After 90 days of feeding, no adverse effects were observed in rats fed glyphosate-tolerant soybeans.

Roundup®, but Not Roundup-Ready® Corn, Increases Mortality of Drosophila melanogaster

Genetically modified foods have become pervasive in diets of people living in the US. By far the most common genetically modified foods either tolerate herbicide application (HT) or produce endogenous insecticide (Bt). To determine whether these toxicological effects result from genetic modification per se, or from the increase in herbicide or insecticide residues present on the food, we exposed fruit flies, Drosophila melanogaster, to food containing HT corn that had been sprayed with the glyphosate-based herbicide Roundup®, HT corn that had not been sprayed with Roundup®, or Roundup® in a variety of known glyphosate concentrations and formulations. While neither lifespan nor reproductive behaviors were affected by HT corn, addition of Roundup® increased mortality with an LC50 of 7.1 g/L for males and 11.4 g/L for females after 2 days of exposure. Given the many genetic tools available, Drosophila are an excellent model system for future studies about genetic and biochemical mechanisms of glyphosate toxicity.

Effects of 90-Day Feeding of Transgenic Maize BT799 on the Reproductive System in Male Wistar Rats

BT799 is a genetically modified (GM) maize plant that expresses the Cry1Ac gene from Bacillus thuringiensis (Bt). The Cry1Ac gene was introduced into maize line Zhen58 to encode the Bt crystal protein and thus produce insect-resistant maize BT799. Expression of Bt protein in planta confers resistance to Lepidopteran pests and corn rootworms. The present study was designed to investigate any potential effects of BT799 on the reproductive system of male rats and evaluate the nutritional value of diets containing BT799 maize grain in a 90-day subchronic rodent feeding study. Male Wistar rats were fed with diets containing BT799 maize flours or made from its near isogenic control (Zhen58) at a concentration of 84.7%, nutritionally equal to the standard AIN-93G diet. Another blank control group of male rats were treated with commercial AIN-93G diet. No significant differences in body weight, hematology and serum chemistry results were observed between rats fed with the diets containing transgenic BT799, Zhen58 and the control in this 13-week feeding study. Results of serum hormone levels, sperm parameters and relative organ/body weights indicated no treatment-related side effects on the reproductive system of male rats. In addition, no diet-related changes were found in necropsy and histopathology examinations. Based on results of the current study, we did not find any differences in the parameters tested in our study of the reproductive system of male rats between BT799 and Zhen58 or the control.

A two-generation reproduction study with transgenic Bt rice TT51 in Wistar rats

TT51 is a transgenic Bt rice created by fusion a synthetic CryAb/CryAc gene into rice MingHui63. A significant number of animal feeding studies with transgenic crops have been carried out with the rapid development of transgenic crops. However, the evidence is far from identifying whether certain novel transgenic crops possess potential danger for human or animal health after long-term consumption. Rice-based diets, containing 60% ordinary grocery rice, MingHui63 rice or TT51 rice by weight, were fed to two generations of male and female rats in order to determine the potential reproductive effects of TT51. In this study, both clinical performance variables and histopathological responses were examined and compared between groups. There were no significant differences between groups on body weights, food consumption, reproductive data and relative organ/body weights. There were some statistically significant differences in hematology and serum chemistry parameters, but no histological abnormalities were seen in the brain, heart, liver, spleen, kidneys, stomach, small intestine, thymus, ovaries, uterus, testes and epididymides. Based on the results, under the circumstance of this study TT51 show no significant differences on reproduction performance of rats compared with MingHui63 and the control.

GMOs in animal agriculture: time to consider both costs and benefits in regulatory evaluations

In 2012, genetically engineered (GE) crops were grown by 17.3 million farmers on over 170 million hectares. Over 70% of harvested GE biomass is fed to food producing animals, making them the major consumers of GE crops for the past 15 plus years. Prior to commercialization, GE crops go through an extensive regulatory evaluation. Over one hundred regulatory submissions have shown compositional equivalence, and comparable levels of safety, between GE crops and their conventional counterparts. One component of regulatory compliance is whole GE food/feed animal feeding studies. Both regulatory studies and independent peer-reviewed studies have shown that GE crops can be safely used in animal feed, and rDNA fragments have never been detected in products (e.g. milk, meat, eggs) derived from animals that consumed GE feed. Despite the fact that the scientific weight of evidence from these hundreds of studies have not revealed unique risks associated with GE feed, some groups are calling for more animal feeding studies, including long-term rodent studies and studies in target livestock species for the approval of GE crops. It is an opportune time to review the results of such studies as have been done to date to evaluate the value of the additional information obtained. Requiring long-term and target animal feeding studies would sharply increase regulatory compliance costs and prolong the regulatory process associated with the commercialization of GE crops. Such costs may impede the development of feed crops with enhanced nutritional characteristics and durability, particularly in the local varieties in small and poor developing countries. More generally it is time for regulatory evaluations to more explicitly consider both the reasonable and unique risks and benefits associated with the use of both GE plants and animals in agricultural systems, and weigh them against those associated with existing systems, and those of regulatory inaction. This would represent a shift away from a GE evaluation process that currently focuses only on risk assessment and identifying ever diminishing marginal hazards, to a regulatory approach that more objectively evaluates and communicates the likely impact of approving a new GE plant or animal on agricultural production systems.

Effects of 90-day feeding of transgenic Bt rice TT51 on the reproductive system in male rats

Rice is a staple food crop; however, the threat of pests leads to a serious decline in its output and quality. The CryAb/CryAc gene, encodes a synthetic fusion Bacillus thuringiensis (Bt) crystal protein, was introduced into rice MingHui63 to produce insect-resistant rice TT51. This study was undertaken to investigate potential unintended effects of TT51 on the reproductive system in male rats. Male rats were treated with diets containing 60% of either TT51 or MingHui63 by weight, nutritionally balanced to an AIN93G diet, for 90days. An additional negative control group of rats were fed with a rice-based AIN93G diet. Body weights, food intake, hematology, serum chemistry, serum hormone levels, sperm parameters and relative organ/body weights were measured, and gross as well as microscopic pathology were examined. No diet-related significant differences in the values of response variables were observed between rats that were fed with diet containing transgenic TT51, MingHui63 and the control in this 90-day feeding study. In addition, necropsy and histopathology examination indicated no treatment-related changes. The results from the present study indicated that TT51 does not appear to exert any effect on the reproductive system in male rats compared with MingHui63 or the control.

Effects of feeding Bt MON810 maize to sows during first gestation and lactation on maternal and offspring health indicators

A total of twenty-four sows and their offspring were used in a 20-week study to investigate the effects of feeding GM maize on maternal and offspring health. Sows were fed diets containing GM or non-GM maize from service to the end of lactation. GM maize-fed sows were heavier on day 56 of gestation (P< 0·05). Offspring from sows fed GM maize tended to be lighter at weaning (P= 0·08). Sows fed GM maize tended to have decreased serum total protein (P= 0·08), and increased serum creatinine (P< 0·05) and γ-glutamyltransferase activity (P= 0·07) on day 28 of lactation. Serum urea tended to be decreased on day 110 of gestation in GM maize-fed sows (P= 0·10) and in offspring at birth (P= 0·08). Both platelet count (P= 0·07) and mean cell Hb concentration (MCHC;P= 0·05) were decreased on day 110 of gestation in GM maize-fed sows; however, MCHC tended to be increased in offspring at birth (P= 0·08). There was a minimal effect of feeding GM maize to sows during gestation and lactation on maternal and offspring serum biochemistry and haematology at birth and body weight at weaning.