Most research indicates that Bt hybrids can more than pay for themselves as silage corn when European corn borers apply pressure. And, contrary to rumors, they feed just as well as conventional corn.
In 1998, Pioneer researchers tested 30 Bt and non-Bt hybrids with the same genetic base at locations across North America. They compared such important silage quality traits as digestibility and nutrient content - and found no measurable differences.
They did find, however, that the Bt hybrids live longer and produce 3-5% more silage. "A 3% increase in tonnage coupled with no change in digestibility results in $18 more silage per acre," points out Pioneer's Dave Whitaker. "That more than compensates for the $8-10/acre seed- cost premium."
The $18 benefit is calculated on a 20-ton/acre base yield and a $30/ton corn silage value, says Whitaker.
Mark Welytok, dairy specialist with Mycogen Seeds, reports that studies at Mycogen and Virginia Tech also showed that a Bt hybrid was healthier at the end of the season and yielded better than a non-Bt hybrid.
And an Iowa State University trial revealed that the Bt trait doesn't affect the amount or quality of milk produced by dairy cows. Further, no Bt protein was detected in standard samples of milk collected from cows fed Bt corn silage.
"I would grow Bt corn for silage if I were a dairy farmer in an area where corn borers are a problem," declares Mike Hutjens, University of Illinois dairy scientist. "Bt corn has less ear droppage, which means more yield. And it makes a high-quality silage that stores well. If a hybrid has a yield advantage and is higher in quality, I will go with it. My cows can take that extra yield and make more milk."
Independent crop consultant Shannon Gomes, Waverly, IA, has two clients, a dairy farmer and a beef feeder, who grow Bt corn for silage.
"They like it because it stays healthier and yields more than conventional corn under corn borer pressure," Gomes notes. "Their experience indicates that there are no feeding problems with Bt corn."
But Ed Nimtz, forage products manager for Cargill Hybrid Seeds, has a different view.
"I have seen no feeding advantages for Bt corn silage," says Nimtz. "And corn grown for silage comes out early enough that corn borer damage is usually not critical for standability. Therefore, I would take the tech fee for Bt corn and apply it to the best silage-quality hybrids available - and grow those for my silage corn."
Some seed companies have Bt hybrids especially suited for silage. Check with your supplier.