Comparison of broiler performance and carcass yields when fed diets containing transgenic maize grains from event DP-O9814O-6 (Optimum GAT), near-isogenic control maize grain, or commercial reference maize grains

Three strategies of transgenic manipulation for crop improvement

Heterologous expression of exogenous genes, overexpression of endogenous genes, and suppressed expression of undesirable genes are the three strategies of transgenic manipulation for crop improvement. Up to 2020, most (227) of the singular transgenic events (265) of crops approved for commercial release worldwide have been developed by the first strategy. Thirty-eight of them have been transformed by synthetic sequences transcribing antisense or double-stranded RNAs and three by mutated copies for suppressed expression of undesirable genes (the third strategy). By the first and the third strategies, hundreds of transgenic events and thousands of varieties with significant improvement of resistance to herbicides and pesticides, as well as nutritional quality, have been developed and approved for commercial release. Their application has significantly decreased the use of synthetic pesticides and the cost of crop production and increased the yield of crops and the benefits to farmers. However, almost all the events overexpressing endogenous genes remain at the testing stage, except one for fertility restoration and another for pyramiding herbicide tolerance. The novel functions conferred by the heterologously expressing exogenous genes under the control of constitutive promoters are usually absent in the recipient crops themselves or perform in different pathways. However, the endogenous proteins encoded by the overexpressing endogenous genes are regulated in complex networks with functionally redundant and replaceable pathways and are difficult to confer the desirable phenotypes significantly. It is concluded that heterologous expression of exogenous genes and suppressed expression by RNA interference and clustered regularly interspaced short palindromic repeats-cas (CRISPR/Cas) of undesirable genes are superior to the overexpression of endogenous genes for transgenic improvement of crops.

Evaluation of the safety and nutritional equivalency of maize grain with genetically modified event DP-Ø23211-2

Feeding studies were conducted with rats and broiler chickens to assess the safety and nutrition of maize grain containing event DP-Ø23211-2 (DP23211), a newly developed trait-pyramid product for corn rootworm management. Diets containing 50% ground maize grain from DP23211, non-transgenic control, or non-transgenic reference hybrids (P0928, P0993, and P1105) were fed to Crl:CD®(SD) rats for 90 days. Ross 708 broilers were fed phase diets containing up to 67% maize grain from each source for 42 days. Body weight, gain, and feed conversion were determined for comparisons between animals fed DP23211 and control diets in each study. Additional measures included clinical and neurobehavioral evaluations, ophthalmology, clinical pathology, organ weights, and gross and microscopic pathology for rats, and carcass parts and select organ yields for broilers. Reference groups were included to determine if any observed significant differences between DP23211 and control groups were likely due to natural variation. No diet-related effects on mortality or evaluation measures were observed between animal fed diets produced with DP23211 maize grain and animal fed diets produced with control maize grain. These studies show that maize grain containing event DP-Ø23211-2 is as safe and nutritious as non-transgenic maize grains when fed in nutritionally adequate diets. The results are consistent with previously published studies, providing further demonstration of the absence of hazards from edible-fraction consumption of genetically modified plants.

Safety assessment of foods from genetically modified crops in countries with developing economies

Population growth particularly in countries with developing economies will result in a need to increase food production by 70% by the year 2050. Biotechnology has been utilized to produce genetically modified (GM) crops for insect and weed control with benefits including increased crop yield and will also be used in emerging countries. A multicomponent safety assessment paradigm has been applied to individual GM crops to determine whether they as safe as foods from non-GM crops. This paper reviews methods to assess the safety of foods from GM crops for safe consumption from the first generation of GM crops. The methods can readily be applied to new products developed within country and this paper will emphasize the concept of data portability; that safety data produced in one geographic location is suitable for safety assessment regardless of where it is utilized.

Effect of dietary phytase transgenic corn on physiological characteristics and the fate of recombinant plant DNA in laying hens

The study aimed to evaluate the potential effects of feeding with phytase transgenic corn (PTC) on organ weight, serum biochemical parameters and nutrient digestibility, and to determine the fate of the transgenic DNA in laying hens. A total of 144 50-week-old laying hens were grouped randomly into 2 treatments, with 8 replicates per treatment and 9 hens per replicate. Each treatment group of hens was fed with diets containing 62.4% non-transgenic conventional corn (CC) or PTC for 16 weeks. The phytase activity for CC was 37 FTU/kg of DM, whereas the phytase activity for PTC was 8,980 FTU/kg of DM. We observed that feeding PTC to laying hens had no adverse effect on organ weight or serum biochemical parameters (p>0.05). A fragment of a poultry-specific ovalbumin gene (ov) was amplified from all tissues of hens showing that the DNA preparations were amenable to PCR amplification. Neither the corn-specific invertase gene (ivr) nor the transgenic phyA2 gene was detected in the breast muscle, leg muscle, ovary, oviduct and eggs. The digestibility data revealed no significant differences between the hens that received the CC- and PTC-based diets in the digestibility of DM, energy, nitrogen and calcium (p>0.05). Phosphorus digestibility of hens fed the PTC-based diet was greater than that of hens fed the CC-based diet (58.03% vs 47.42%, p<0.01). Based on these results, it was concluded that the PTC had no deleterious effects on the organ weight or serum biochemical parameters of the laying hens. No recombinant phyA2 gene was detected in muscle tissues and reproductive organs of laying hens. The novel plant phytase was efficacious in improving the phosphorus digestibility of laying hens.

Comparison of broiler performance and carcass yields when fed diets containing genetically modified canola meal from event DP-Ø73496-4, near-isogenic canola meal, or commercial canola meals

Genetically modified (GM) canola (Brassica napus L.) line containing event DP-Ø73496-4 (hereafter referred to as 73496 canola) was produced by the insertion of the glyphosate acetyltransferase (gat4621) gene derived from Bacillus licheniformis. Expression of the GAT4621 protein present in 73496 canola plants confers in planta tolerance to the herbicidal active ingredient glyphosate. The objective of this study was to compare the nutritional performance of broiler chickens fed canola meal from 73496 canola seed with that of broiler chickens fed non-GM canola meal in a 42-d feeding trial. Diets were prepared using meal processed from seed from unsprayed 73496 plants or from plants sprayed with an in-field application of glyphosate herbicide [73496(S)]. For comparison, additional diets were produced with canola meal obtained from the non-GM near-isogenic control or non-GM commercial reference DuPont Pioneer brand varieties 42H72, 42H73, 46A65, and 44A89. Diets were fed to Ross 708 broilers (n = 120/group, 50% male and 50% female) in 3 phases: starter and grower phases containing 10 or 20% canola meal, respectively, and a finisher phase with a common corn-soybean meal diet without any canola meal. No statistically significant differences were observed in growth performance measures or organ and carcass yields between broilers consuming diets produced with canola meal from unsprayed or sprayed 73496 seed and those consuming diets produced with canola meal from control seed. Additionally, all performance, organ, and carcass measures from control, 73496, and 73496(S) canola treatment groups were within tolerance intervals constructed using data from the reference canola groups. It was concluded from these results that meal processed from 73496 canola seed (unsprayed plants or plants sprayed with glyphosate) was nutritionally equivalent to meal processed from non-GM near-isogenic control canola seed.

The use of whole food animal studies in the safety assessment of genetically modified crops: limitations and recommendations

There is disagreement internationally across major regulatory jurisdictions on the relevance and utility of whole food (WF) toxicity studies on GM crops, with no harmonization of data or regulatory requirements. The scientific value, and therefore animal ethics, of WF studies on GM crops is a matter addressable from the wealth of data available on commercialized GM crops and WF studies on irradiated foods. We reviewed available GM crop WF studies and considered the extent to which they add to the information from agronomic and compositional analyses. No WF toxicity study was identified that convincingly demonstrated toxicological concern or that called into question the adequacy, sufficiency, and reliability of safety assessments based on crop molecular characterization, transgene source, agronomic characteristics, and/or compositional analysis of the GM crop and its near-isogenic line. Predictions of safety based on crop genetics and compositional analyses have provided complete concordance with the results of well-conducted animal testing. However, this concordance is primarily due to the improbability of de novo generation of toxic substances in crop plants using genetic engineering practices and due to the weakness of WF toxicity studies in general. Thus, based on the comparative robustness and reliability of compositional and agronomic considerations and on the absence of any scientific basis for a significant potential for de novo generation of toxicologically significant compositional alterations as a sole result of transgene insertion, the conclusion of this review is that WF animal toxicity studies are unnecessary and scientifically unjustifiable.

Detection of transgenic and endogenous plant DNA fragments and proteins in the digesta, blood, tissues, and eggs of laying hens fed with phytase transgenic corn

The trials were conducted to assess the effects of long-term feeding with phytase transgenic corn (PTC) to hens on laying performance and egg quality, and investigate the fate of transgenic DNA and protein in digesta, blood, tissues, and eggs. Fifty-week old laying hens (n = 144) were fed with a diet containing 62.4% PTC or non-transgenic isogenic control corn (CC) for 16 weeks. We observed that feeding PTC to laying hens had no adverse effect on laying performance or egg quality (P>0.05) except on yolk color (P<0.05). Transgenic phyA2 gene and protein were rapidly degraded in the digestive tract and were not detected in blood, heart, liver, spleen, kidney, breast muscle, and eggs of laying hens fed with diet containing PTC. It was concluded that performance of hens fed diets containing PTC, as measured by egg production and egg quality, was similar to that of hens fed diets formulated with CC. There was no evidence of phyA2 gene or protein translocation to the blood, tissues, and eggs of laying hens.

Evaluation of the compositional and nutritional values of phytase transgenic corn to conventional corn in roosters

Three experiments were conducted to evaluate the compositional and nutritional values of corn grains [phytase transgenic corn (PTC) and isogenic conventional corn (CC)] and compare the efficacy of corn-based phytase and extraneous microbial phytase for enhancing the utilization of phytate phosphorus (P) in single corn or corn-soybean mixed meals (corn:soybean = 2.5:1, wt:wt) fed to roosters. Following a 48-h fasting period, 16 roosters were given 50 g of each sample via crop intubation and excreta were collected for 48 h. Nitrogen-free and phosphorus-free diets were used to evaluate endogenous amino acid and endogenous P losses, respectively. Chemical composition was not different between PTC and CC, whereas the phytase content for PTC was greater than CC (8,047 vs. 37 FTU/kg of corn, DM basis; P < 0.001). No difference was observed in the TME and true amino acid availability values between the PTC and CC in roosters. The true P utilization for PTC was greater than CC (37.92 vs. 55.85%; P < 0.001), and CC and PTC contained 0.13 and 0.19% available P (AP, DM basis; P < 0.001), respectively. There was no difference in P utilization (72.76 vs. 70.23%; P > 0.05) between roosters fed PTC and extraneous microbial phytase in equivalent FTU/kg of diets. The results of this study indicated that the chemical composition, TME, and true amino acid availability in PTC are essentially equivalent to that in CC, and the true P utilization for roosters is higher in PTC than in CC. Corn expressing phytase is as efficacious as equivalent microbial phytase when supplemented in corn-soybean diets for chickens.

Comparison of broiler performance and carcass yields when fed transgenic maize grain containing event DP-O9814O-6 and processed fractions from transgenic soybeans containing event DP-356O43-5

The performance of broilers fed diets containing maize grain from event DP-Ø9814Ø-6 (98140; gat4621 and zm-hra genes) and processed fractions (meal, hulls, and oil) from soybeans containing event DP-356Ø43-5 (356043; gat4601 and gm-hra genes) was evaluated in a 42-d feeding study. Diets were produced with nontransgenic maize grain and soybean fractions from controls with comparable genetic backgrounds to 98140 and 356043 (control), 98140 maize and 356043 soybean (98140 + 356043), or 3 commercially available nontransgenic maize and soybean combinations. Ross 708 broilers (n = 120/group; 50% male, 50% female) were fed diets in 3 phases: starter (d 0 to 21), grower (d 22 to 35), and finisher (d 36 to 42). Starter diets contained (on average) 63% maize and 28% soybean meal, grower diets 66% maize and 26% soybean meal, and finisher diets 72% maize and 21% soybean meal; soybean hulls and oils were held constant at 1.0 and 0.5%, respectively, across all diets in all phases. Weight gain, feed intake, and mortality-adjusted feed efficiency were calculated for d 0 to 42. Standard organ and carcass yield data were collected on d 42. Data were analyzed using a mixed model ANOVA with differences between control and 98140 + 356043 group means considered significant at P < 0.05. Reference group data were used only to estimate experimental variability and to generate tolerance intervals. No significant differences were observed in weight gain, mortality, mortality-adjusted feed efficiency, organ yields, or carcass yields between broilers consuming diets produced with 98140 + 356043 and those consuming diets produced with control maize and soybean fractions. All values of response variables evaluated in the control and 98140 + 356043 groups fell within calculated tolerance intervals. Based on these results, it was concluded that the combination of genetically modified 98140 maize and 356043 soybean fractions was nutritionally equivalent to nontransgenic maize and soybean controls with comparable genetic backgrounds.

Nutritional equivalency evaluation of transgenic maize grain from event DP-O9814O-6 and transgenic soybeans containing event DP-356O43-5: laying hen performance and egg quality measures

The objective of this study was to compare the nutritional performance of laying hens fed maize grain from event DP-Ø9814Ø-6 (98140; gat4621 and zm-hra genes) and processed soybean meal from soybeans containing event DP-356Ø43-5 (356043; gat4601 and gm-hra genes), individually or in combination, with the performance of hens fed diets containing nontransgenic maize and soybean meal. Healthy pullets (n = 216) placed in cages (3 hens/cage) were randomly assigned to 9 dietary treatments (8 cages/treatment): nontransgenic controls 1, 2, and 3 (comparable genetic background controls for 98140, 356043, and 98140 + 356043, respectively); reference 1, reference 2, and reference 3 (commercially available nontransgenic maize-soybean meal sources); and 98140 (test 1), 356043 (test 2), and 98140 + 356043 (test 3). The experiment was divided into three 4-wk phases (24 to 28 wk, 28 to 32 wk, and 32 to 36 wk of age), during which time hens were fed mash diets. Performance (BW, feed intake, and egg production) and egg quality data were collected. Data were analyzed using a mixed model ANOVA; differences between the control and respective test group means were considered significant at P < 0.05. Data generated from the reference groups were used only in the estimation of experimental variability and in generating the tolerance interval. Body weight and BW gain, egg production, and production efficiency for hens fed the test diets were similar to the respective values for hens fed the corresponding control diets. Haugh unit measures and egg component weights were similar between the respective test and control groups, and no differences were observed in quality grades or crack measures. All observed values of the control and test groups were within the calculated tolerance intervals. This research indicates that the performance and egg quality of hens fed diets containing 98140 maize grain, 356043 soybean meal, or a combination of the 2 was comparable with that of hens fed diets formulated with nontransgenic maize grain or soybean meal control diets with comparable genetic backgrounds.