98 Effect of engineered biocarbon on rumen fermentation, nutrient digestibility, methane emissions, and rumen microbiota in beef heifers

Abstract

The objective of this study was to examine the effect of engineered biocarbon (EB) on rumen fermentation, apparent total tract digestibility, methane (CH₄) emissions and the rumen and fecal microbiome of Angus × Hereford heifers fed a barley silage-based diet. The experiment was a replicated 4 × 4 Latin square using 8 ruminally cannulated heifers (565 ± 35 kg initial BW). The basal diet contained 60% barley silage, 35% barley grain and 5% mineral supplement with EB added at 0% (control), 0.5%, 1.0%, or 2.0% (DM basis). Each period was 28-d consisting of 14-d adaptation and 14-d of measurements. Samples for profiling of the microbiome in rumen liquid, solids and feces were collected on d-15 before feeding. Rumen samples for fermentation characterization were taken at 0, 3, 6, and 12-h post feeding. Total collection of urine and feces was conducted from d-18 to 22. Heifers were housed in open-circuit respiratory chambers on d-26 to 28 to estimate CH₄ emissions. Ruminal pH was recorded at 1-min intervals during CH₄ measurements using indwelling pH loggers. Data were analyzed with the fixed effects of dietary treatment and random effects of square, heifer within square and period. Dry matter intake was similar across treatments (P = 0.21). NH₃-N concentration and protozoa counts responded quadratically (P = 0.01) to EB. Minimum pH was increased (P = 0.04), and variation of pH was decreased (P = 0.03) by 2.0% EB. Total tract digestibility, N balance and CH₄ production were not affected (P ≥ 0.17) by EB. EB affected the relative abundance of Fibrobacter (P = 0.05), Spirochaetaes (P = 0.01), Verrucomicrobia (P = 0.02), Tenericutes (P = 0.01), and Elusimicrobia (P = 0.02). Results suggest that at the examined concentrations, EB was ineffective at decreasing enteric CH₄ emissions, however it altered the rumen microbiome.