NUTRITIONAL-EVALUATION OF WHOLE-PLANT MAIZE ENSILED AT 3 CHOP LENGTHS AND FED TO LACTATING DAIRY-COWS

Whole crop maize (Zea mays) was chopped at 3 lengths before ensiling; the maize was harvested with a precision chop harvester with screen apertures of either 9 cm(2) (fine chopped maize), 36 cm(2) (medium chopped maize), or no screen at all (coarse chopped maize). The 3 silages were each fed as a supplement to pasture to lactating dairy cows in 2 experiments. Although some of the variables measured to assess silage quality suggested that the preservation process may have deteriorated as length of chop increased, length of chop of maize generally appeared to have little effect on silage quality or milk production. In experiment 1, cows ate about 7 kg DM of pasture and 8-9 kg DM of maize silage per day. Mean daily milk yields for the cows offered fine, medium and coarse chopped silage were 18.0, 17.7 and 18.2 kg/cow, respectively. In experiment 2, where daily intakes of each maize silage covered the range of 0-10.7 kg DM/cow, regression analysis could not detect any differences in milk responses between chop lengths. We concluded that aspects other than nutritional considerations should determine the length of chop that farmers aim for when making maize silage; these include ease of compaction in the bunker to ensure the production of good quality silage, and fuel consumption during harvesting.