Cashew nutshell liquid as an additive on rumen fermentation dynamics and nitrogen utilization in pasture-supplemented steers

The objective was to evaluate the effects of supplementing technical cashew nutshell liquid (CNSLt) on rumen fermentation and nitrogen utilization in grazing steers. Five crossbred rumen-cannulated steers were evaluated. The pasture used was Urochloa brizantha, cv. Marandu. The treatments were: supplementation without CNSLt infusion (control), supplementation + 300 mg/kg DM, supplementation + 600 mg/kg DM, supplementation + 900 mg/kg DM, and supplementation + 1,200 mg/kg DM of CNSLt. The inclusion of CNSLt in the steers' diet did not alter (P>0.05) intake or apparent digestibility. Among the fermentation parameters, only valeric fatty acid differed between treatments (P=0.040). The inclusion of 600 mg/kg DM CNSLt resulted in the highest valeric acid values (1.06). Higher inclusion of CNSLt led to lower fecal N excretion (P=0.029). The other N utilization variables, purine derivatives, and urea and creatinine metabolism were not affected by the treatment (P>0.05). In conclusion, the addition of CNSLt to the diet of grazing steers does not alter pasture intake or digestibility. The addition of 600 mg/kg DM CNSLt to the diet increased valeric acid production, improving rumen fermentation. The linear decrease in fecal N excretion suggests better N utilization with increasing CNSLt in the diet. Keywords: additive; Anacardium occidentale; grazing cattle; nitrogen utilization; rumen fermentation.