Corte de dos híbridos de maíz a alturas de 15 ó 50 cm en el rendimiento del ensilaje y del rastrojo dejado por el corte alto

This trial evaluated the effect of cutting heights of 15 or 50 cm of two corn hybrids (Pioneer 37P73 and Dekalb 615), on dry matter (DM) yield and the nutritional quality of silages and lower stalks left by the higher cutting. The two hybrids were sown in small plots in a completely randomized design with three replications. At the half milk line stage of maturity, 20 plants per plot were manually cut at 15-cm height, in 10 plants of which the portion of stalk below 35 cm was separated to simulate the lower stalk that would be left in the field by the 50-cm height cut. Six plants per plot (including lower stalks from the high cutting) were used to determine dry weight and morphological components (leaf, stalk, husk, and grain). The remaining plants of each plot were ensiled in plastic containers of 5 L capacity. For the in situ study, samples of the silages and lower stalks were incubated for 0, 6, 12, 18, 24, 48, and 72 h in two 350 kg steers. Plants of the Pioneer hybrid were 24% heavier and had a higher proportion of grain than those of Dekalb, although the latter had a higher proportion of leaves. The 50-cm cutting resulted in a 15% reduction in yield, but a concomitant increase of similar magnitude in the proportion of grain, with no difference between the two hybrids. Silage resulting from the 50-cm cutting was higher in contents of DM (39.7 vs. 33.6%) and starch (35.8 vs. 29.6%) and lower in content of neutral detergent fiber (NDF) (35.8 vs. 39.0%). Neither cutting height nor hybrid affected the kinetics of in vitro gas production, but the higher cut improved the in situ degradation rate (4.65 vs. 3.08%/h) and the effective degradability (56.1 vs. 51.0%, at kp = 5%/h: DE-5). The hybrids did not differ in lower stalk weight, leaf/stem proportion or nutritive quality (NDF = 63.9%; DE-5 = 41.1%), the latter values being lower than those of the 15-cm cut silage. It is concluded that the hybrids had little effect on the variables under study, and although the 50-cm cut occasioned a yield loss, this was offset by improved silage quality and the additional biomass of the lower stalk, which could be an extra benefit in periods of forage shortage.