| Safety evaluation of genetically modified mCry1Ac corn (BT corn) in pure-line hens were investigated. The effect of long-term and mulitgeneration feeding of BT corn on growth and development, egg quality, intestinal health, organ function, immune response and intestinal microflora of chicken were studied to provide data reference for establishment of safety evaluation system and government standard of genetically modified feeds.The objective of Exp.1 was to determine the nutrients and energy of the nontransgenic near-isoline control corn (CT), transgenic corn lines containing the mCry1Ac genes from Bacillus thuringiensis strain (BT) and commercially available nontransgenic reference corn (RF), and the diets including the CT, BT and RF corn, respectively. An in vitro digestion method with computer-controlled simulated digestion system (SDS) simulated digestion in the stomach, the intestine and the total tract of dry matter and energy. It would provide a reference to develop in vitro method for evaluating the nutritional substantial equivalence of genetically modified crops using the SDS. A single factorial completely randomized design with 3 corn ingredients (CT, BT and RF corn) and corresponding 3 corn diets (CT, BT and RF corn diet) was adapted. The digestion in the stomach, intestine and total tract were simulated respectively and each diet treatment contained 5 replicates with 1 digestion tube per replicate. The in vitro dry matter digestibility (DMD), in vitro gross energy digestibility (GED), and enzymatic hydrolysate gross energy (EHGE) were determined of corn ingredients and diets. Nutrient concentration was similar between the BT and CT corn ingredients and diets. As a whole, the gastric and total tract DMD, the gastric and total tract GED and the EHGH were not affected by the BT corn ingredient and diet (P> 0.05). The EHGE of transgenic BT corn diet were greater than the EHGE of isogenic non-transgenic corn diet (P= 0.02, CV= 1.12%), the variation coefficient was less than the variation coefficient of feed ingredients using the SDS (CV≤ 1.64%). In vitro method using the SDS provide a reference to develop for evaluating the nutritional substantial equivalence of genetically modified crops.The objective of Exp.2 was to investigate the effect of feeding BT corn on egg performance, egg quality, intestinal histology, organ health indicators and serum biochemical parameters. Healthy hens (n= 72 placed in cages; 3 hens/cage) were randomly assigned to 1 of 3 corn-soybean meal dietary treatments (8 cages/treatment) formulated with the following corn:61.7% CT corn, BT corn and RF corn. The experiment was divided into three 4-week phases (week 1 to 4, week 5 to 8 and week 9 to 12 of feeding phases), during time which hens were fed mash diets. Performance (Body weight, feed intake and egg production) and egg quality were determined. Following slaughter at the end of 12 weeks of feeding phases (n= 8/treatment), carcass yield and organ weights (heart, liver, spleen, lung, kidneys, stomach and ovary) were recorded; organs and intestines were sampled for histological analysis. Analysis of serum biochemistry parameters to assess the liver and kidney function were performed. No differences in egg production and egg quality were observed between hens consuming the CT corn diet and hens consuming the BT corn diet. Intestinal histology and health were similar between the control and test groups. Liver and kindey histology and health was not affected by the diet treatment. Similar organosomatic indices and serum parameters did not indicate the characteristics of organ dysfunction. This research indicates that the performance, egg quality, intestinal histology, organ health and carcass yield of laying hens fed diets containing the BT corn line were similar to that of laying hens fed diets formulated with the non-transgenic near-isoline corn with comparable genetic backgrounds.The objective of Exp.3 was to investigate the effect of feeding BT corn on cecal microbita. Healthy hens (n= 48 placed in cages; 3 hens/cage) were randomly assigned to 1 of 2 corn-soybean meal dietary treatments (8 cages/treatment) formulated with the following corn:61.7% CT corn and BT corn. Following slaughter at the end of 12 weeks of feeding phases (n= 8/treatment), the relative abundance of cecal bacteria was determined using high-throughput 16S rRNA gene sequencing. Relative gene expression of bacteria was also determined using real-time PCR. No differences in Ace, Chao I, Shannon index and good coverage were observed between hens consuming the CT corn diet and hens consuming the BT corn diet. No differences were observed in any bacterial taxa between treatments, with the exception of the genus Ruminococcaceae unclassified and the species Mucispirillum_schaedleri which were less abundant in the cecum of laying hens fed the BT treatment compared to hens fed the CT treatment (P< 0.05). However, the relative gene expression of Bifidobacterium and Ruminococcaceae_unclassified was not affected by the BT treatment.The objective of Exp.4 was to investigate the effect of trans-generation feeding BT corn on growth and health of parental hens and offspring hens. Healthy hens (n= 72 placed in cages; 3 hens/cage) were randomly assigned to 1 of 3 corn-soybean meal dietary treatments (8 cages/treatment) formulated with the following corn:61.7% CT corn, BT corn and RF corn for 12 weeks. The female chicks were assigned within parental treatment to CT, BT or RF corn diets for 36 weeks i.e.1) CT corn-fed parental hens-CT corn-fed offspring hens (CT-CT); 2) BT corn-fed parental hens-BT corn-fed offspring hens (BT-BT); and 3) RF corn-fed parental hens-RF corn-fed offspring hens (RF-RF). Body weight and egg quality were determined. Following slaughter at the end of 36 weeks of feeding phases (n= 8/treatment), carcass yield and organ weights (heart, liver, spleen, lung, kidneys and ovary) were recorded; organs and intestines were sampled for histological analysis. Analysis of serum biochemistry parameters, haematology and ex hormone were performed. Immune cell phenotypes of spleen and peripheral blood mononuclear cells were determined. No differences in body weight, egg quality and function of reproductive organs were observed between hens consuming the CT-CT corn diet and hens consuming the BT-BT corn diet. Intestinal histology and health were similar between the control and test groups. Liver and kindey histology and health was not affected by the diet treatment. The relative weight of lung and kindeys of laying hens fed the BT treatment was less than hens fed the CT treatment (P< 0.05). Similar organosomatic indices and serum parameters did not indicate the characteristics of organ dysfunction. Immune response was affected by the trans-generation feeding BT corn diet.The objective of Exp.5 was to investigate the effect of trans-generation feeding BT corn on growth and health of parental hens and offspring roosters. Healthy hens (n= 72 placed in cages; 3 hens/cage) were randomly assigned to 1 of 3 corn-soybean meal dietary treatments (8 cages/treatment) formulated with the following corn:61.7% CT corn, BT corn and RF corn for 12 weeks. The male chicks were assigned within parental treatment to CT, BT or RF corn diets for 32 weeks i.e.1) CT corn-fed parental hens-CT corn-fed offspring hens (CT-CT); 2) BT corn-fed parental hens-BT corn-fed offspring hens (BT-BT); and 3) RF corn-fed parental hens-RF corn-fed offspring hens (RF-RF). Body weight and semen quality were determined. Following slaughter at the end of 32 weeks of feeding phases (n= 6/treatment), carcass yield and organ weights (testis, cockscomb, wattle, heart, liver, spleen, lung and kidneys) were recorded; organs and intestines were sampled for histological analysis. Analysis of serum biochemistry parameters, haematology and ex hormone were performed. Immune cell phenotypes of spleen and peripheral blood mononuclear cells were determined. No differences in body weight, development and function of sex organ were observed between roosters consuming the CT corn diet and roosters consuming the BT corn diet. Intestinal histology and health were similar between the control and test groups. Liver and kindey histology and health was not affected by the diet treatment. Similar organosomatic indices and serum parameters did not indicate the characteristics of organ dysfunction. Immune response was affected by the trans-generation feeding BT corn diet. |
PDF Full Text Request