In vitro degradation and methane production of short-season corn hybrids harvested before or after a light frost

In western Canada, short-season corn silage production is increasing due to its potentially high nutritive value. The objective of this study was to determine variability and relationships among nutrient concentration, degradability, and methane (CH4) production of short-season whole-plant corn hybrids harvested before or after light frost (-1.5 degrees C). Four hybrids, based on their corn heat unit rating (<= 2600, CHU rating), were grown in 2 yr in central and southern Alberta (AB) with two field replications. The batch culture and Daisy fermenter techniques were used to characterize degradability and gas production measurements. At both locations, dry matter (DM) concentration was affected by harvest and hybrid (P <= 0.02). However, starch and neutral detergent fiber (NDF) concentrations differed (P <= 0.01) or tended (P = 0.07) to differ among harvest and hybrid only in central AB. Over both locations and harvest times, CH4 production was related negatively to propionate and positively to acetate proportions. In conclusion, harvesting southern AB hybrids after frost increased DM concentration and NDF degradability with no effect on CH4 emissions, but the high DM concentration may negatively affect silage quality and animal performance. Harvesting central AB hybrids after frost increased DM and starch concentrations, while reducing CH4 emissions but had limited effects on nutrient degradability.