Forages and Pastures 1

摘要

Harvesting practices such as cutting height are known to alter wholeplantcorn silage nutritive value and biomass yield. However, there is noconsensus in the literature about the optimum cutting height thresholdto balance nutritive value and biomass yield. Therefore, the objectiveof this study was to evaluate the influence of cutting height on nutrientcomposition and yield of whole-plant corn silage through a meta-analyticapproach using a data set comprised of 10 published studies and 64treatments means. Cutting height was the sole independent variable usedin the present study. Dependent variables were DM, starch, and NDF,concentrations, as well as ruminal in vitro or in situ NDF digestibility(NDFD), DM yield, and milk production per area or per Mg of freshsilage (estimated using the Milk2006 predictive equations). Data wereanalyzed using PROC MIXED in SAS; the model included the fixedeffect of treatment and the random effect of trial. Means and standarddeviations for dependent and independent variables were as follows:cutting height (36 ± 21, cm), DM (36.4 ± 4.3, % of as fed), NDF (40.2± 4.7, % of DM), starch (25.3 ± 9.3, % of DM), NDFD (58.9 ± 12.8, %of DM), DM yield (14.9 ± 2.5 t/ha), milk production/Mg (1682, ± 289,kg/Mg), and milk production per area (19317 ± 3522, Mg/ha). Yield ofDM was reduced (P = 0.001) by 0.05 Mg/ha for each cm of increasedcutting height. However, for each cm increase in cutting height therewas an increase (P < 0.05) of 0.09, 0.08, and 0.08%-units in DM, starch,and NDFD, respectively. Conversely, there was a negative linear effect(P < 0.05) for NDF, with a 0.10%-unit decrease per cm increase incutting height. There was a decrease (P < 0.05) in milk production perarea of 37.8 kg/ha for each cm increase in cutting height, whereas therewas a tendency (P = 0.09) to increase milk production by 1.868 kg/Mg of fresh silage for each cm increase in cutting height. These equationsindicate that increasing cutting height improves forage quality, atthe expense of DM biomass yield. Therefore, caution is needed whenplanting area is limited.