Assessing hemp components as feed for cattle through in-vitro true digestibility, in-situ, and cannabinoid determinations

Recent legislation allowed hemp (Cannabis sativa L.) to be cultivated as an agricultural commodity in the United States. Preliminary investigations indicate that hemp has potential to be utilized as feed for domestic ruminants; however, an in-depth analysis of the suitability of different components of the hemp plant as feed has not been conducted. Additionally, the market for hemp waste as a byproduct of production has not yet been identified. The objective of this study was to evaluate the nutrient content, in-vitro true digestibility (IVTD), in-situ rumen degradability, and cannabinoid concentrations of various hemp plant components (i.e., stalk, flower, leaves, and whole plant). Our findings indicate that IVTD was highest for hemp leaves (925 g/kg dry matter) and in-situ organic matter (OM) degradability was similar across plant components (P = 0.70). Hemp leaves had the largest in-situ potentially soluble OM fraction as compared to other plant components (P ≤ 0.01) whereas flower had the largest immediately soluble OM fraction (P ≤ 0.01). Tetrahydrocannabidiol (THC) and cannabidiol (CBD) concentrations were highest for flower (5575 µg/g THC; 114,325 µg/g CBD), then whole plant (2745 µg/g THC; 63,175 µg/g CBD), leaves (1410 µg/g THC; 34,750 µg/g CBD) and stalk (THC n/d; 590 µg/g CBD). These data suggest that hemp flower and leaves are degraded to the greatest extent by rumen microbes, but hemp stalk and whole plant had the lowest cannabinoid concentrations and are less likely to transfer residues to edible tissues in livestock consuming hemp.