Effect of nitrogen fertilisation on chemical composition and rumen fermentation of different parts of plants of three corn hybrids

The experiment compared reductions in the level of N fertilisation of corn crop ( i.e. , no N fertilisation; 0-N, or 150 kg of N/ha; 150-N) with those currently adopted in the Po valley of North Italy ( i.e. , 300 kg of N/ha; 300-N) on chemical and nutritional characteristics of grain, stalks and leaves in corn hybrids selected for whole plant silage production ( i.e. , FAO 700 maturity). Grain composition and starch availability for digestion was examined at three stages of maturity of the kernels ( i.e. , ½ milk line, ¾ milk line and black layer). One hybrid had a lower grain yield (15.2 versus 16.0–16.8 tonnes DM/ha; P i.e. , 150-N and 0-N versus 300-N) lowered (P versus 0.412) and leaves (0.604 and 0.620 versus 0.622). Stage of maturity of grain did not interact with the N level of fertilization, and advanced maturity was associated with a marked increase (P i.e. , 0-N) reduced the zein contents and increased rumen fermentability.