Evaluation of the physical structure of fodder beets, potatoes, pressed beet pulp, brewers grains, and corn cob silage

The physical structure of fodder beets, raw potatoes, ensiled pressed sugar beet pulp, ensiled brewers grains, and corn cob silage was evaluated in di ets containing concentrates and either corn silage or grass silage as the r oughage source. In one series of experiments, the chewing activity of eight cows was measured over 4 d. The beet pulp and fodder beets were added to t he two roughage sources at two ratios [20:80 and 35:65, dry matter (DM) bas is]. Potatoes, brewers grains, and corn cob silage were fed in a fixed amou nt (5 to 6 kg of DM) with corn silage. The chewing indexes (eating and rumi nating time per kilogram of DM ingested) for fodder beets and beet pulp ave raged 34.3 and 32.3 min/kg of DM, respectively, and were hardly affected by the nature of the roughage or by the inclusion ratio. The chewing indexes for potatoes, brewers grains, and corn cob silage were 23.7, 56.6, and 41.6 min/kg of DM, respectively. In another series of experiments using 8 to 11 cows, the ratio of roughage to concentrates was lowered weekly by 5 percen tage units, and the critical roughage portion of the diet was determined (i .e., the amount just before a lack of physical structure was observed). The roughage source was either fed alone or supplemented with about 4 kg of DM of the experimental feed. The critical roughage portion of the diet decrea sed when the experimental feeds were added; the decrease was greatest with ensiled pressed beet pulp and was lowest with corn cob silage.