PSIII-8 - Influences of industrial hemp variety and botanical part on measures of in situ ruminal nutrient disappearance

Abstract: The 2018 Agricultural Improvement Act expanded the legal production of industrial hemp in the United States. Industrial hemp and the residual biomass after grain harvest could represent an alternative roughage source for ruminant rations; however, reports are limited on nutrient differences and ruminal digestion between different hemp varieties. Our objective was to investigate the influence of hemp varieties (grain or dual-purpose) and botanical parts on ruminal nutrient disappearance. Plants were harvested from 4 industrial hemp varieties (CFX-2, CRS-1, Grandi and Katani) at physiological maturity. Plants were separated into stem, leaf and seed by variety. Dacron bags containing unique combinations of variety and botanical part were incubated for 0, 4, 8, 12, 24, 48, 72, and 96 h in 2 ruminally cannulated heifers to measure in situ DM, OM, NDF and ADF disappearance. Disappearance kinetics were calculated using the Marquardt method in SAS and data was analyzed using the GLIMMIX procedure with fixed effects of variety, botanical part and the interaction and random effect of animal. Disappearance kinetics of DM, OM, NDF and ADF were influenced by the interaction of variety and botanical parts; however, these interactions seemed to be largely related to differences in ruminal degradation of seeds between varieties. The dual-purpose variety CFX-2 had greater (P < 0.01) concentrations of soluble DM while Katani had the least, however, rates of DM disappearance were greater (P = 0.03) among Katani compared to CFX-2 and Grandi. Amounts of undegradable DM and OM were least (P ≤ 0.03) in CFX-2. Among measures of fiber disappearance, CFX-2 had the least amount of soluble ADF (P < 0.01) and the greatest concentrations of slowly degradable ADF (P < 0.01) compared to other varieties. The undegradable fraction of ADF was greatest (P = 0.03) in CRS-1 and least in Katani. Rates of ADF disappearance (P = 0.02) were least for Katani. Amounts of soluble DM were greatest (P = 0.02) among leaves and the least in stem but seed was not different from either. Rates of DM disappearance were greatest (P < 0.01) among leaves, intermediate among seeds and least in stem. Amounts of soluble OM and rates of OM disappearance were greater (P < 0.01) in leaves compared to stems and seeds, however, slowly degradable OM was greater (P < 0.01) in stems compared to leaves and seeds. Seeds had low fiber disappearance with lesser amounts (P < 0.01) of soluble NDF and ADF and greater amounts (P ≤ 0.03) of undegradable NDF and ADF compared to leaves and stems. Overall, slowly degradable DM and undegradable OM were not different (P ≥ 0.09) across different botanical parts. These data indicate that different varieties and botanical parts of industrial hemp have altered ruminal disappearance patterns.