The whole common bean plant is of minor importance as fodder in ruminant feeding, but beans, straw and other crop residues and processing by-products are occasionally used.
The common bean seeds are relatively rich in protein, but, like other legume grains, the nitrogen is rapidly degraded in the rumen. The degradation rate can be slowed by the addition of commercial tannic acid up to 50 g/kg DM (Martinez et al., 2004).
In Brazil, in dairy cows fed a TMR, the replacement of soybean meal with cull common beans (damaged seeds of various varieties and origins mixed with foreign materials), up to 39% of the concentrate DM, linearly decreased both intake and milk production, but did not affect feed efficiency. The digestibility of OM and NDF was not affected, while protein digestibility decreased and digestibility of non-fibre carbohydrates linearly increased (Rodrigues Magalhaes et al., 2008).
In Colorado, in beef cows (540-600 kg BW) grazing native winter range, cull beans were of low palatability but otherwise comparable to sunflower meal as a protein supplement for body weight, body condition score, reproductive performance and calf performance (Patterson et al., 1999).
In Australia, navy beans were used as supplements for young sheep fed low quality roughage ad libitum. A low or moderate inclusion of navy beans (10 or 20 g/kg LW0.75) resulted in a similar increase in DM intake and OM digestibility as other legume supplements (blue lupin Lupinus angustifolius or cowpea Vigna unguiculata). Productivity from a supplement of 10 g/kg LW0.75 of navy beans was similar to that observed with the same level of lupins or cowpeas. However, when higher levels were used live-weight gain and wool growth were lower than expected, presumably due to the detrimental effects of antinutritional factors in the navy beans that were not inactivated by rumen fermentation (Paduano et al., 1995).
Fresh bean forage
There is little information available on the utilization of fresh common bean forage. It was well accepted and used with a high digestive efficiency by goats (Boza et al., 1981), and also by captive lesser mouse deer (Tragulus javanicus) (Darlis et al., 1999).
Bean crop residues and bean straw
In Spain, in a comparison of postharvest bean by-products the ME content of the residues were estimated at 9.2 (stems), 8.5 (leaves) and 10 (pods) MJ/kg DM, which are values close to that of medium quality grass hay. Leaf protein was highly degradable in the rumen (70%) (Pieltain et al., 1998). Due to a higher protein and lower fibre content, bean straw has a higher in vitro DM digestibility and metabolizable energy content than cereal straws. Leaf-rich straw has a higher in vitro DM digestibility than stem-rich straw (74 vs. 68%) and a higher ME (8.0 vs. 7.3 MJ/kg DM, estimated by the gas production method) (Lopez et al., 2005).
In Mexico, bean straw and maize stubbles included at 15% of goat diets resulted in lower body weight gains and feed efficiency than those obtained with a good quality forage-based diet (Serrato Corona et al., 2004). Bean haulms were poorly ingested and digested by low producing goats in Ethiopia (Aredo et al., 2003). However, in Malawi, bean haulms satisfied the requirements of low producing goats (Ayoade et al., 1983). In Mexico, bean straw was used as a basal diet (75 to 80%, up to 3.5% BW) for studying responses to supplementation with alfalfa or acacia leaves (Ramirez et al., 1997).
In Chile, when llamas (Lama glama) were fed bean straw, ingestibility and protein digestibility were similar to those obtained from ryegrass hay (29 g/kg BW0.75/d and 35% respectively). The digestibilities of NDF (54%) and ADF (52%) were found similar to those of oat straw (Lopez et al., 2001).