Nutritive value of corn silage in mixture with climbing beans

Corn (Zea mays L.) for silage is a major forage source for dairy cows in the northern USA. It has high-energy density, but crude protein concentration is low. This study was conducted to determine the silage fiber characteristics and fermentation profile of monoculture corn or in mixture with one of three climbing beans. The experiment was conducted in two locations in 2004 and 2005. Three climbing beans, velvet bean [Mucuna pruriens (L.) D.C.], 'Rongai' lablab bean [Lablab purpureus (L.) Sweet], and 'Scarlet Emperor' scarlet runner bean (Phaseolus coccineus L.) were intercropped with corn at two corn densities (82.5 and 55 thousand plants/ha). All three beans were sown at the same density (82.5 thousand plants/ha). Corn in monoculture or in mixture with bean was harvested between 1/2 and 3/4 milk line. Two 1-L glass jar mini-silos per treatment per replicate plot were filled at a density of 500g/L, eight jars per treatment, and stored for a minimum of 45 days at room temperature (~22°C). At the time of ensiling a 500-g fresh sub-sample was also taken for dry matter and initial characterization of the corn and corn-bean mixtures. Each silo was analyzed for fiber characteristics, pH, and fermentation products. Silage crude protein (CP) concentration on average increased 12.6% in the mixture with the addition of any of the beans, but neutral detergent fiber (aNDF) concentration also increased 8.8%. The pH was 0.06 units greater in corn-bean mixtures than monoculture corn, and lactic acid concentration was on average 6.2% greater in the corn-bean mixtures than monoculture corn. The addition of climbing bean to corn increased CP but also had an effect on fiber concentration and fermentation profile. However, the nutritive value of corn-bean silage was similar to corn silage, indicating that corn-bean silage mixtures could be used in dairy cow rations.