The object of this present work was to determine the effects of supplementation with pellets containing royal poinciana seed meal (PEREM) on feed use, ruminal fermentation efficiency, microbial protein synthesis, blood metabolites and mitigation of methane (CH4) emissions in cattle. The animals used in this experiment were four male Thai native beef cattle (Bos indicus) with initial body weights (BWs) of 125 ± 5.0 kg. Each of the animals were randomly assigned to receive PEREM doses at 0, 50, 100 and 150 g/d, respectively, according to a 4 × 4 Latin square design. Concentrates were fed at 0.5% BW daily, and rice straw was fed ad libitum. There were no significant differences (p > 0.05) on intakes of rice straw, concentrate and total diet. The intake of nutrients did not change among the levels of PEREM supplementation (p > 0.05), except for an intake of crude protein, which was linearly enhanced when increasing the dose of PEREM (p < 0.05). The inclusion of different doses of PEREM did not adversely affect the digestibility of dry matter, organic matter, crude protein, neutral detergent fiber and acid detergent fiber (p > 0.05). Adding various doses of PEREM did not alter ruminal pH and ruminal temperature, while concentrations of ammonia-nitrogen were significantly increased with an increased dose of PEREM supplementation (p < 0.01). The increasing doses of PEREM linearly reduced protozoal numbers (p < 0.01), with the lowest concentration when PEREM was added at 150 g. PEREM supplementation did not change (p > 0.05) the concentration of acetic acid or butyric acid or the ratio of acetic acid to propionic acid. Nevertheless, the total volatile fatty acid and propionic acid content were changed among PEREM levels (p < 0.05), which were linearly increased with an increasing dose of PEREM. At 4 h post feeding, the CH4 concentrations in the rumen of the animal were linearly reduced when the dose of pellets was increased (p < 0.01). In addition, the inclusion of PEREM did not adversely affect other blood metabolites, namely total protein, creatinine and albumin (p > 0.05). Furthermore, microbial crude protein and efficiency of microbial N synthesis were linearly enhanced when increasing levels of PEREM were added. The feeding of PEREM at 150 g/d might be an alternative with the potential to improve rumen fermentation efficiency and reduce the environmental effects produced by ruminants.
Keywords: efficiency of microbial N synthesis; enteric methane; feed processing; plant phytochemical; protozoa population.