Interaction of whole cottonseed and supplemental fat on digestive function in cattle

Four Holstein steers (155 kg) with "T" cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square design experiment to evaluate the interaction of whole cottonseed (WC) and yellow grease (YG) on digestive function. Four treatments were compared: 1) 0% YG, 0% WC; 2) 5% YG, 0% WC; 3) 0% YG, 20% WC, and 4) 5% YG, 20% WC. The YG and WC were substituted for steam-flaked corn in an 80% concentrate growing-finishing diet. Both YG and WC decreased ruminal OM digestion (P < .01). However, the effects were not additive (interaction, P < .05). When YG was added to the control diet ruminal OM digestion was decreased by 6.9%. In contrast, when YG and WC were added to the control diet the decrease was 24.0%. This interaction was also apparent (P < .05) in ruminal digestion of feed N and starch. Total tract digestion of OM was decreased (P < .01) with WC and YG supplementation, although, like ruminal digestion, the effects were nonadditive (P < .05). In the absence of WC, YG had little influence (.8%) on OM digestion. However, in the presence of WC, YG decreased total tract OM digestion 5.7%. This interaction was also manifest (P < .05) in total tract digestion of ADF and GE. Although there was some compensation with respect to methane energy loss, the ME (megacalories/kilogram) of WC was 20% lower when fed in combination with YG. The degree of ruminal biohydrogenation of unsaturated fatty acids was high for both WC and YG.(ABSTRACT TRUNCATED AT 250 WORDS)