Evaluation of the Nutritive Value of the Whole Plant Faba Bean Silage as Component of Growing Steer Diets

Agriculturalists are interested in alternate crops for livestock production, particularly when traditional crops are in short supply or high in price. A crop that may have value as an alternative leguminous forage crop to alfalfa (Medicago sativa) and clovers (Trifolium spp) is the faba bean (Vicia faba). Vicia faba may be produced for seed which may be used as a protein supplement or for whole plant silage. Being a legume, the crop has the further advantage of fixing atmospheric nitrogen in the soil, thus benefiting the succeeding crop. With the exception of certain regions of California, and more recently in some northern states such as Montana, faba beans are rarely grown in the United States. Faba bean production is new in South Dakota and the extent of adaptation is not well known, but the crop may have considerable potential in this area. The crop is a cool season, frost resistant, annual legume that is adapted to short growing seasons. Experimental plantings have been grown at the Southeast South Dakota Experiment Farm Station near Beresford. The plantings of Vicia faba emerged well and continued growing until November 10, when the night time temperature reached -6.6 °C (Sorensen, 1988). Scott and Aldrich (1983) reported that periods longer than 2 hours at temperatures ranging from -3.8 to -1 .1 °C would kill the leaves of soybeans (Glycine max). Vicia faba is grown for human consumption and animal feed. The seeds are large, high in protein and carbohydrates and low in fat. United Nations statistics report a seed yield potential of 4000 kg/ha. The plant grows erect and possesses excel lent stalk strength which facilitates harvest as silage. Under optimum conditions the plant may reach 1.5 to 1.8 meters in height. Yields of 35 to 50 metric tons/ha of green forage have been reported by Tisserand and Roux (1976). Ensiling trials indicated that silage quality of the whole crop is satisfactory but is best where the material has been wilted to 30% dry matter (Witt and Moelle, 1973). The yield potentials and the high protein content of the crop suggest that the whole plant could be an economical feed when used as a silage. The objectives of the experiments reported in this thesis were: 1. To determine the nutritive value of whole plant faba bean silage compared with corn-alfalfa (Zea mays-Medicago sativa) silage for growing steers. 2. To determine the in situ disappearance of dry matter (DM), crude protein (CP) and neutral detergent fiber (NDF) of faba bean silage compared with alfalfa hay in steers receiving high and low forage diets