PSVII-10 Evaluation of different biochar sources added at two inclusion levels in a grass hay- based diet on dry matter disappearance and ruminal fermentation parameters in vitro

Abstract

This study evaluated the impact of adding biochar to a grass hay-based diet on in vitro dry matter disappearance (DMD), total gas production (GP), methane production (CH4), volatile fatty acid (VFA) and ammonia nitrogen (NH3-N) concentration. Treatments were arranged in a factorial design with 7 biochar products differing in origin (pine or coconut-based) and physical properties (course, fine or loose spheres) at 2 inclusion levels (2.25% and 4.5% of DM) and a grass hay-only control. On each three successive weeks, rumen fluid was collected from 2 ruminally cannulated beef heifers fed a grass hay-based diet, pooled and mixed with a buffer solution (1:2) and treatments incubated in triplicate for 48 h. Gas pressure was recorded at 3, 6, 9, 12, 18, 24, 36 and 48 h of incubation, and gas was collected at each time to measure CH4. At 48 h, pH was measured and the supernatant sampled for determination of VFA and NH3-N, while the residue was used to estimate DMD. Dry matter disappearance decreased (P < 0.05) with increasing addition of biochar. Biochar did not affect GP or CH4, but did reduce (P < 0.05) gas production per g of DM incubated (111.7 vs 107.8 ml/g), but not per g DMD. The lower GP per g DM incubated could be related to the increased proportion of the diet as biochar, without it contributing to GP. Biochar, irrespective of level did not affect the total or molar proportions of VFA. There was a biochar x inclusion level interaction (P < 0.04) in NH3-N concentration. Biochar type and inclusion level in the present study had little or no significant effect on in vitro fermentation and did not mitigate CH4 production from a grass hay-based diet.