Influence of Biochar and Liquid Smoke Additives from Cacao-Pod Husks on In vitro Ruminal Fermentation Characteristics

The objective of this study was to investigate the influence of biochar (BC) and liquid smoke (LS) additives from cacao pod husks on in vitro ruminal fermentation products, ruminal microbiota and feed degradation. The in vitro effects of different levels of BC and LS on rumen fermentation characteristics were assessed in a randomized block design experiment with five treatments and four replicates (BC and LS were separately analyzed). The treatments consisted of a basal ration (forage: pollard; 60:40 w/w) with various BC additions: BC0 (basal ration + 0 mg/ml biochar), BC1 (basal ration + 0.1 mg/ml biochar), BC2 (basal ration + 0.2 mg/ml biochar), BC3 (basal ration + 0.3 mg/ ml biochar), and BC4 (basal ration + 0.4 mg/ml biochar) and LS additions: LS0 (basal ration + 0 µl/ml liquid smoke), LS1 (basal ration + 0.25 µl/ml liquid smoke), LS2 (basal ration + 0.5 µl/ml liquid smoke), LS3 (basal ration + 0.75 µl/ ml liquid smoke), and LS4 (basal ration + 1 µl/ml liquid smoke). These treatments were subjected to in vitro incubation with buffered rumen fluid for 48 hours. Results showed that the addition of BC and LS did not affect pH, ammonia, or total gas production. Compared to the BC0 treatment, BC addition significantly increased acetate production (P < 0.01), and significantly decreased butyrate, isobutyrate, valerate, and isovalerate (P < 0.05). Compared to the LS0 treatment, LS addition significantly increased total volatile fatty acids (VFA), acetate, and acetate to propionate ratio (P < 0.05). Biochar addition above 0.1 mg/ml but not LS addition significantly decreased (P < 0.01) in vitro ruminal dry and organic matter degradabilities. Biochar addition above 0.1 mg/ml, but not LS addition significantly decreased total bacteria population (P < 0.001). Addition of BC above 0.2 mg/ml decreased protozoa population (P < 0.001) while LS decreased protozoa population, dependent on dose (P < 0.001). In conclusion, biochar and liquid smoke from cacao-pod husks had different effects on ruminal fermentation characteristics. However, both of them partially defaunated ruminal microbiota and shift VFA composition.