Nutritional value of a corn containing a glutamate dehydrogenase gene for growing pigs

Eight female PIC Line 42 pigs (initial BW = 47.5 +/- 1.8 kg) were used in a two-period switchback design (n = 4 per treatment per period) to evaluate the nutritional difference between a genetically modified corn and a similar nontransgenic corn. The genetically altered corn (gdhA+) contained a glutamate dehydrogenase gene isolated from Escherichia coli. The non-transgenic corn was the same variety lacking the transgenic cassette, grown at the same two locations. Pigs were surgically fitted with steered ileocecal valve cannulas for collection of ileal digesta. Diets were made up of primarily one of the two corn sources. Dietary AA profiles were adjusted using crystalline AA to match Illinois Ideal Protein Ratios. Pigs were limit-fed at 8% of metabolic body weight (BW0.75) in two equal feedings at 0600 and 1800 daily throughout the experiment. The study consisted of two 15-d periods. Each period consisted of a 7-d acclimation period, a 3-d total collection of feces and urine, two 12-h ileal collections, and a 3-d adjustment period between ileal collections to ensure adequate hydration. Crude protein, leucine, methionine, alanine, aspartic acid, glutamic acid, and tyrosine concentrations were greater (P < 0.05) in the gdhA+ corn than in the nontransgenic variety. The presence of the gene did not alter (P > 0.17) BW gain. Similarly, DM digestibility, fecal N excretion (grams per day), apparent total-tract N digestibility, N balance, net protein utilization, and N retained as percentages of absorbed were not affected (P > or = 0.32) by the gene modification. Apparent ileal AA digestibility values did not differ (P > 0.31) between the two dietary treatments. Results of this study suggest corn that contains the E coli. gene for glutamate dehydrogenase was nutritionally equivalent to the unaltered variety.