PSIX-11 In vitro fermentation parameters of defatted hemp samples at different levels of irrigation

Abstract

The objective of this study was to determine the influence of defatted hemp under three irrigation regimes (0, 100, and 200 mm: DF0, DF1, and DF2 respectively) on in vitro fermentation parameters relative to alfalfa (Medicago sativa). Fermentation kinetics was accessed through in vitro gas production technique. Two ruminally cannulated Angus steers were used as inoculum donors in four incubation runs. For each incubation, four 160-mL serum bottles containing 200 mg of air-dried samples were incubated in 14 mL of buffering media and 4 mL of rumen inoculum. Each incubation spanned 48h with gas production measured at 0, 3, 6, 12, 24, and 48-h post-incubation. In vitro true digestibility of dry matter (IVTDMD) and organic matter (IVTOMD), total gas production (TGP), metabolizable energy (ME) and total volatile fatty acids (VFA) were determined. Hemp and alfalfa were compared via orthogonal contrast using the GLIMMIX procedure of SAS (version 9.4) with treatment as fixed effect and run as a random. Relative to alfalfa (Alf) hemp displayed increased TGP (P < 0.01; 31.1 vs. 27.47 mL) that remained following correction for DM and OM (P ≤ 0.05). Similarly, IVTDMD and IVTOMD were higher for hemp (P < 0.01; 77.7 vs. 70.2% and 81.7 vs. 73.9%). Hemp yielded slightly higher ME (P = 0.03) but equivalent total VFA production when compared to Alf (P = 0.62), even when corrected for DM and OM. Irrigation at 200 mm decreased TGP and fermentability of fat-extracted hemp (p-value). Results also indicate that irrigation at its highest level is detrimental to the availability of ME for rumen microbes, but not with the expense of the in vitro digestibility (IVTDMD and IVTOMD) nor in total VFA produced. In conclusion, defatted hemp samples appear to have greater digestibility and ME with equivalent VFA production relative to alfalfa.