Effect of cutting height on the nutritive value, dry matter yield, and fermentation profile of whole-plant corn forage and silage through a meta-analysis

The objectives of this study were to (1) evaluate the effect of cutting height during harvest on the nutrient composition, fermentation profile, and DM yield of whole-plant corn forage and silage and (2) evaluate the effect of cutting height on these variables at different DM at harvest categories. Data from 35 studies and 151 observations met the selection criteria, and 33 studies and 134 observations reported DM at harvest or DM of silage. Data were classified as low (LO; <32% DM; 42 observations from 15 studies), average (AVG; 32% to 37% DM; 52 observations from 14 studies) or high (HI; >37% DM; 29 observations from 9 studies) DM at harvest and the effect of cutting height was evaluated within each subset of DM at harvest, in addition to the full dataset. Data were analyzed with the fixed effect of cutting height and random effects of study and treatment (other treatments not including cutting height) within study. Both linear and quadratic effects of cutting height were tested for each variable, however no quadratic effects were observed. Increasing cutting height increased starch concentration and NDF digestibility (NDFD). Conversely, increasing cutting height decreased the concentrations of NDF, ADF, lignin, and undigested NDF. Furthermore, DM yield decreased as cutting height increased. There was no effect of cutting height on the fermentation profile of whole-plant corn silage. The response of NDFD to cutting height differed slightly for different DM categories, where NDFD increased the most for HI DM at harvest, followed by LO, and then AVG categories. In contrast, when cutting height increased, starch concentration increased the most for LO DM at harvest, followed by HI, and then AVG categories. Overall, increasing cutting height improved the nutritive value of whole-plant corn forage or silage at the expense of DM yield but did not affect fermentation profile. Additionally, it appears that the response of starch concentration and NDFD may vary according to DM at harvest, although these results should be interpreted with caution as DM at harvest is not always highly correlated with plant or kernel maturity in corn forage and silage.