Effect of physical structure of maize silage on digestibility and energy content by cattle and sheep

In three experimental series (ES) the digestibility and energy content of various maize silages were proved with cattle and sheep depending on physical structure and stage of maturity at harvest. The maize silages had mean DM contents of 28 % (ES1), 32 % (ES2) and 37 % (ES3), whereas the stovers and the cobs had DM contents of nearly 22 % (ES1 and ES2) and of 27 % (ES3) and of 40 % (ES1), 46 % (ES2) and 57 % (ES3), respectively. In ES1 and ES3 the chopping lengths were 4 mm and 8 mm and in ES2 6 mm and 8 mm. In ESI no additional corn cracking were used, while in ES2 and ES3 maize silages were fed with and without additional corn cracking. Reducing the chopping length from 8 mm to 4 mm (ES1) diminished the digestibility of the crude fibre by the cattle in tendency and by sheep significantly. Therefore, the digestibility of the organic matter of 4 mm-maize silage in comparison to 8 mm-maize silage was reduced at about 3 % and the metabolizable energy (ME) and the net energy (NE), respectively, diminished at about 4-5 %. In ES2 no significant effect of the chopping length or corn cracking were measured on the digestibilities. However, the corn starch of the maize silages with corn cracking in comparison without corn cracking was better digested by cattle. In ES3 the physical structure of the silages significantly influenced the digestibilites by cattle, but no effect was seen by sheep. Corn cracking increased the starch digestibility to nearly 96 %, while treatments without corn cracking reduced the starch digestibility to 91 % (4 mm-maize silage) or 83 % (8 mm-maize silage). The digestibility of the crude fat were reduced similarly. No effect was measured on the digestibility of the crude fibre. Therefore, optimizing the physical structure of the maize silage of ES3 will increase the ME at nearly 6 % and the NE at about 9-10 % in comparison to the treatment of 8 mm chopping length without corn cracking. The technic of harvesting the maize crop will be discussed depending on the stage of maturity at harvest.