Most corn hybrids grown in the US are genetically modified to resist certain pests or to tolerate certain herbicides. Numerous studies have been conducted to determine the nutritional value of corn that is genetically modified for pest resistance, but there are no published reports about feeding corn that has been modified for both pest resistance and insecticide tolerance to pigs. Investigation into the nutritional value of such corn is, however, warranted, because the use of crops with multiply stacked traits is rapidly increasing; approximately 35 million acres of crops with double- and triple-stacked traits were planted in the United States in 2006.

Two experiments were, therefore, conducted to determine if the nutritional value of corn grain with multiple genetically modified traits is different from that of nontransgenic corn. The hypothesis in both experiments was that pigs fed transgenic corn would not differ in growth performance or carcass characteristics from pigs fed nontransgenic corn.

The Grains

Grain 59122 is a transgenic corn grain that contains event DAS-59122-7, which expresses abinary insecticidal protein for the control of corn rootworm.  Grain 59122 also carriesthe phosphinothricin acetyltransferase (PAT) gene from Streptomyces viridochromogenes, which confers tolerance to herbicides containing the active ingredient glufosinate-ammonium, such as Bayer AG's Liberty®.  59122 was recently approved for feeding to animals in the United States.

The transgenic corn grain TC1507 contains the event DAS-Ø15Ø7-1, which encodes a protein that has insecticidal activity toward European corn borer, southwestern corn borer, fall armyworm, black cutworm, corn earworm, and western bean cutworm. Like 59122, TC1507 also carries the PAT gene.

Table 1- Characteristics of transgenic corn grains

The Experiments

In both experiments, growing pigs were fed a corn-soybean meal diet in a 3-phase program:

Phase 1: start - 60 kg
Phase 2: 60 - 90 kg
Phase 3: 90kg - slaughter

All diets were formulated to meet or exceed all nutrient requirements for growing-finishing pigs.

Experiment 1 was designed to test the hypothesis that pigs fed 59122 would not differ in growth performance or carcass characteristics from pigs fed a nontransgenic near-isoline control grain.  108 growing pigs were allotted at random to three dietary treatments. The first group was fed a nontransgenic, near-isoline control grain. The second group was fed 59122.  A third group was fed a commercial corn hybrid. The commercial hybrid was fed for the purpose of establishing normal variation among the pigs being used, and its results were to be analyzed only if a statistically significant difference appeared between the transgenic and nontransgenic feeds.

In Experiment 2, 96 growing pigs were allotted to four experimental diets.   Corn-soybean meal diets were formulated with four corn hybrids: a commercial source of corn, a standard corn, a near-isoline control corn, or TC1507.

Average daily gain, average daily feed intake, and gain to feed ratio were calculated for each phase and treatment group in both experiments.

At the conclusion of the experiments, pigs were slaughtered, hot carcass weight was recorded and LM area, LM depth, and fat thickness were measured at the tenth rib.

Results

Growth performance of pigs fed 59122 did not differ from performance in pigs fed the near-isoline control or the commercial corn.  Carcass characteristics were also the same, with the exception that a slight relationship was found between corn type and pig sex in LM depth.

Table 2 - Growth performance of pigs fed corn-soybean meal diets containing grain 59122 and two nontransgenic grains

Table 3- Carcass characteristics of pigs fed corn-soybean meal diets containing grain 59122 and two nontransgenic grains

Experiment 2, with grain TC1507, produced similar results.  Pigs fed TC1507 had the same growth performance as pigs fed the near-isoline control grain as well as the commercial and standard hybrids.  On all carcass measurements, pigs fed TC1507 were the same as the pigs fed the three nontransgenic grains.

Table 4- Growth performance of pigs fed corn-soybean meal diets containing grain TC1507 and three nontransgenic grains

Table 5- Carcass characteristics of pigs fed corn-soybean meal diets containing grain TC1507 and three nontransgenic grains

Key Points

• No differences in feed intake or pig growth performance between pigs fed genetically modified corn grain that contained multiple modified and pigs fed the unmodified controls or other commercial corn grains.
• Inclusion of the modified corn grains in the diets did not influence carcass composition of pigs.
• The overall feeding value of corn grains containing multiple modified traits is not different from that of nonmodified corn grains.
• Producers may use corn grains containing multiple modified traits for feeding of pigs as they would use any other corn grain.  

This report is based on the following peer-reviewed publications:

Stein, H. H., D.W. Rice, B. L. Smith, M. A. Hinds, T. E. Sauber, C. Pedersen, D. M. Wulf, and D. N. Peters. 2009. Evaluation of corn grain with the genetically modified input trait DAS-59122-7 fed to growing-finishing pigs. J. Anim. Sci. 87:1254-1260.

Stein, H. H., T. E. Sauber, D. W. Rice, M. A. Hinds, B. L. Smith, G. Dana, D. N. Peters, and P. Hunst. 2009. Growth performance and carcass composition of pigs fed corn grain from DAS-Ø15Ø7-1 (Herculex I) hybrids. Prof. Anim. Scientist. 25:689-694.