Effects of ensiling of Bacillus thuringiensis (Bt) maize (MON810) on degradation of the crystal 1Ab (Cry1Ab) protein and compositional quality of silage

The study investigated the degradation of the Bt protein (Cry1Ab) in Bt maize during ensiling and chemical composition of the silage. Two laboratory studies were conducted at the University of Fort Hare. One Bacillus thuringiensis (Bt) maize cultivar (DKC80-12B) and its isoline (DKC80-10) in the 2008/2009 study and two Bt maize cultivar (DKC61-25B and PAN6Q-321B) and their isolines (DKC61-24 and PAN6777) in the 2009/2010 study, were ensiled for 42 days and analyzed for ash-free dry matter, Cry1Ab protein, neutral detergent fiber, acid detergent fiber, acid detergent lignin and crude protein. Silage from two of the Bt maize varieties had lower ash-free dry matter than their near-isolines, while variety DKC61-25B was similar to its near-isoline. At least, 60% of the initial Cry1Ab protein concentration remained in the silage. Bt maize had higher neutral and acid detergent fiber than its isolines before ensiling and remained constant after ensiling in 2008/2009, but was neither influenced by ensiling nor variety in 2009/2010. Crude protein and acid detergent lignin in Bt maize silages were similar to those in silages derived from their near-isolines. The findings suggested that Bt maize will result in silage with similar chemical composition to that of non-Bt maize but a large proportion of the Cry1Ab protein persists.