Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/16/2008
Publication Date: 3/16/2009
Citation: Contreras-Govea, F.E., Muck, R.E., Armstrong, K.L., Albrecht, K.A. 2009. Fermentability of Corn-Lablab Bean Mixtures from Different Planting Densities. Animal Feed Science And Technology. 149(3-4):298-306. Interpretive Summary: Corn silage is a common component of dairy cattle rations. While corn silage has many positive attributes, it is low in protein. One potential solution is to grow a high-protein crop with the corn. Previously, we found that lablab bean grows well with corn. In the current study, we looked at how planting density of both crops affects the amount of bean in the mixture, the nutritional value of the mixtures, and how the mixtures ferment in the silo. We found that the amount of lablab bean in the mixture increased as corn planting density was reduced. As the amount of bean increased in the mixture, the protein content increased. Preservation of the mixtures in silos was very good, similar to corn silage. Research is needed to test how cattle perform on the corn-lablab bean mixtures. If that research is successful, growing lablab bean with corn may be a useful way for dairy farmers to increase the protein content of their corn silage. This could be an important way to reduce the importation of nitrogen onto dairy farms in the form of purchased protein-rich feeds, helping to achieve a better nitrogen balance on the farm.
Technical Abstract: This study was conducted to determine silage fiber characteristics and fermentation profiles of corn (Zea mays L.) grown in mixture with lablab bean [Lablab purpureus (L.) Sweet] at different planting densities. The experiment was conducted in two environments in 2005. 'Rongai' lablab bean and corn were intercropped at eight different planting densities, 20/80, 40/0, 40/40, 40/80, 60/0, 60/40, 60/80, and 80/80 thousand corn/lablab bean 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 500 g/L, eight jars per treatment per location, and stored for 40 days at room temperature (~ 22°C). At the time of ensiling a 500-g fresh sub-sample was also taken for dry matter (DM) 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 was on average 17.5% (86.4 g/kg DM) greater in the mixture than monoculture corn (73.5 g/kg DM). The in vitro true digestible DM (IVTDDM) concentrations in the mixtures were on average 4.6% less (796 g/kg DM) than that of monoculture corn (834 g/kg DM), but neutral detergent fiber digestibility was not different between monoculture corn and corn-lablab mixtures (P > 0.05). Lactate concentration was 21.2% higher in the corn-lablab bean mixtures (60.5 g/kg DM) than monoculture corn (49.9 g/kg DM). The contribution of the lablab bean to the mixture increased as corn planting density decreased. Thus the maximum benefits to increased CP occurred in the mixtures with the lowest corn planting densities, but those mixtures also had the greatest reductions in IVTDDM. However all treatments fermented well in spite of significant (P > 0.05) differences in pH and fermentation products.