Ruminal metabolism in nonlactating cows fed whole cottonseed or extruded soybeans

Five nonlactating Holstein cows (average weight 574 kg) with cannulas in the rumen and duodenum were fed five total mixed diets at 2.14% (DM) of BW for seven 2-wk periods to estimate the ruminal degradation of protein and fatty acids in whole cottonseed (WCS) and extruded soybeans (ESB). Lanthanum was used as an indigestible marker. Ruminal propionic acid (molar proportion) was larger and butyric acid was smaller for WCS diets than for control or ESB diets. Total VFA (mM) and acetic acid (molar proportion) were similar for all diets. Duodenal flow of nonammonia nitrogen (N) was 13% higher for ESB diets than for WCS diets, but was similar for the control and diets with WCS. The percentage of intake protein that was undegraded was 19% higher for ESB diets than for WCS diets. Ruminal and total apparent digestibilities of ADF were not reduced by the addition of oil seed. In conclusion, the protein from ESB was less degraded in the rumen of cows than protein from WCS. The addition of ESB at 12.7% (DM) or WCS at 25.3% of the diet did not reduce the apparent digestibility of fiber. The unsaturated fatty acids in WCS were not protected from ruminal biohydrogenation, presumably due to mastication of the seed coat.