Effect of Bt corn on broiler growth performance and fate of feed-derived DNA in the digestive tract

Abstract

The aim of the study was to evaluate the effect on broiler performance of transgenic Bacillus thuringiensis (Bt) corn containing the Cry1A(b) protein compared with the corresponding near isogenic corn and to analyze the degradation of the Cry1A(b) gene in the digestive tract. Ross male broilers (432) were fed for 42 consecutive days with diets containing Bt or isogenic corn. Diet, Bt corn, and the isogenic form of the Bt corn were analyzed for composition and aflatoxin B1, fumonisin B1, and deoxynivalenol contents. Broiler body weight and feed intake were recorded at regular intervals (d 0, 21, and 42). The presence of the Cry1A(b) gene and plant-specific genes Zein and Sh-2 in gut contents of crop, gizzard, jejunum, cecum, and samples of blood was determined in 10 animals per treatment at the end of the trial using a PCR technique. Chemical composition was not different between Bt and its isogenic form, whereas the fumonisin B1 content for Bt was lower than for isogenic corn (2,039 vs. 1,1034 ppb; P < 0.05). The results of the growth study showed no difference for average daily weight gain (129.4 vs. 126.0 g/d), feed intake (63.4 vs. 61.8 g/d), and feed conversion ratio (1.95 vs. 2.02) among the groups. No significant relationship was observed between mycotoxins content and growth performances. Feed-derived DNA is progressively degraded along the digestive tract. Detection frequency of short fragments of maize-specific high copy number Zein gene was high but significantly decreased in distal sectors. An 1,800-bp fragment of the Cry1A(b) gene, corresponding to the minimal functional unit, was detected only in crop and gizzard of birds fed Bt corn. Sh-2 showed the same detection frequency of Cry1A(b) and was also found in birds fed isogenic corn. Blood samples were positive with low frequency only for the Zein gene fragment. No significant difference in DNA detection was observed between birds fed Bt and isogenic corn, indicating that DNA derived from transgenic feed undergoes the same fate as isogenic feed.

Safety Evaluation of Bt Plants

“…Duggan et al reported that only a short cry gene (211-bp) was detected in rumen fluid when sheep were fed Bt corn 19 . Rossi et al detected a cry gene (1800-bp) only in gizzard contents, and there were no significant differences in the detection frequency of the other corn genes between Bt and isogenic corn fed to broilers 40 . They concluded that DNA derived from transgenic feed undergoes the same fate as isogenic feed.…”

Mycotoxin Contamination on Corn Used by Feed Mills in Indonesia

“…In addition, in both USA and Argentina, corn was grown in less favourable weather conditions for fungal development compared with that planted in the humid tropical condition of Indonesia. Furthermore, the use of genetically engineering Bt corn resistant to insect attack in most US farms significantly decreased mycotoxin contamination (Chen et al 2004;Rossi et al 2005) because insect attack caused open wounds on kernels which facilitated fungus infection (Hawk 2004). …”

Risks from GMOs due to Horizontal Gene Transfer

“…In the case of vertebrates, the fate of DNA from GM corn and soybean has been extensively monitored in cattle, sheep, pigs and poultry (Aeschbacher et al, 2005;Beagle et al, 2006;Chowdhury et al, 2004;Deaville and Maddison, 2005;Duggan et al, 2003;Einspanier et al, 2001;Jennings et al, 2003aJennings et al, , 2003bMazza et al, 2005;Nemeth et al, 2004;Sharma et al, 2006;Tony et al, 2003). DNA segments can survive intestinal juices and multicopy forms of DNA could be detected in some tissues examined in chickens (muscle, liver, spleen or kidney), but not in eggs (Einspanier et al, 2001).…”

“…One report of transgenic DNA in organs of pigs could not demonstrate the presence of an intact gene or integration into the genome of somatic cells (Sharma et al, 2006). In all cases, there was extensive degradation of DNA in the gastrointestinal tract, reducing the size and frequency of DNA transfers (Beagle et al, 2006;Chambers et al, 2002;Chowdhury et al, 2003;Deaville and Maddison, 2005;Phipps et al, 2003;Rossi et al, 2005;Wiedemann et al, 2006). Therefore, the GM feeding studies show the potential for transient gene transfer to animal somatic cells but not germ line cells (van den Eede et al, 2004).…”