Abstract:
Animal Production in Australia Vol. 15 THE EFFECT OF LENGTH OF SILAGE CUT ON THE PERFORMANCE OF BEEF STEERS K.D, GREATHEAD* and R.M. McTAGGART* On the South coast of Western Australia a subterranean clover/perennial ryegrass pasture was mown and windrowed and alternate rows were harvested by either a single chop (SC,25-20cms), a double chop (DC,8-12cms) or a precision chop (PC, Groups of 15 steers (5 Angus and 10 Hereford x 3-5cms) forage harvester. Friesian x Angus or Hereford) that had been weaned 6-8 weeks previously were each self fed only silage made from SC, DC or PC forage in stacks of approximately 9t of dry matter. The results are summarised in Table 1. TABLE 1 Silage quality and steer performance (mean - SE) in relation to method + of harvest No significant effect of length of cut on quality of silage or the growth rate or condition of steers was found. These results support the general findings of a review by Marsh (1978) in which he reported that few comparisons have been published. However 43 % and 34% more weight was gained on the double and precision chopped silages which supported the animals for 12 to 15 days longer. The efficiency of forage collection appeared to be greatest for the PC machine followed by the DC machine. The rate of liveweight gain was more variable (PcO.05) in the animals fed long chopped silage than in the animals in the other groups. Coefficients of variation being 31%, 15% and 19% respectively. These silage reserves fed in summer/autumn provided higher liveweight gains per ha than could be expected from grazing dried off summer residues at this time (i.e. 117, 167 and 157 kg/ha c.f. -70 to +50kg/ha depending on the year and grazing pressure), but lower gains than could be expected from grazing pastures in spring over the period they would be closed up for silage making (i.e. about 250 kg/ha). From ultrasonic measurement of backfat over the M. longissimus dorsi at the 10th rib it was estimated that steers fed SC, DC and PC silage gained an average of 0.9m.m, 1.5mm and 1.9mm respectively. In contrast this class of animal with 7mm backfat in February, grazing dry pastures alone over the time silage was fed would lose condition. In summary the different lengths of cut did not significantly affect quality of silage harvested or the growth rates of steers. However rates of gain were more variable with long chopped silage and total weight gain was 38.6% (13.5kg) higher using PC and DC forage harvesters than a SC machine. Marsh, R. (1978). N.Z. J. Exp. Agric. 6 : 271, = *Department of Agriculture, Albany, Western Australia, 6330. 685
