76 An in-vitro analysis of hemp as feed for beef cattle

Abstract

Abstract Hemp, Cannabis sativa L., is a versatile crop that has been cultivated for centuries. Cannabis production had been outlawed in the United States due to concerns related to tetrahydrocannabinol (THC) intoxication. However, recent legislation has declassified hemp as a schedule 1 drug under regulated conditions (i.e., THC < 0.3%). Thus, hemp has been reclassified as an agricultural commodity, and its production for fiber, food, and medicine has increased. Hemp cultivation results in by-products that are not utilized for human needs and have potential as livestock feed, especially for ruminants. Current regulations restrict the use of hemp and its by-products in livestock systems due to the presence of cannabinoids. Thus, research on the nutritional value of hemp for cattle is lacking. The objective of this study was to characterize the nutrient concentrations, in-vitro digestibility (IVD), and cannabinoid concentrations of different fractions of the hemp plant. Procedures involving animals were approved by IACUC at Texas State University (#8497). Four replications of hemp plants of the Cherry Soda varietal were cultivated at Texas State University. Samples were air-dried and fractionated into lower (n = 4), leaves (n = 4), stalks (n = 4), and whole plant (n = 4). Dry matter, organic matter (OM), acid detergent fiber (ADF), neutral detergent fiber (NDF), and crude protein (CP) were determined. For IVD, samples were incubated in digestion vessels containing buffers and rumen fluid at 39.5°C for 48 h and subsequently analyzed for NDF. Cannabinoid analysis was conducted via high-performance liquid chromatography (HPLC). The OM was in acceptable ranges for each hemp fraction (69-95%). The NDF and ADF were within normal ranges of conventional livestock feeds and forages for most fractions, except hemp stalk (81% NDF, 69% ADF). There was high variability in CP between fractions, with the least concentrations observed in the stalk (4%) and greatest in the flower (25%). Stalks had an IVD of 21%, whole plant of 67%, flower of 87%, and leaves of 93%. Cannabinoids were present in each fraction and especially concentrated in the flower (14%) and depleted in the stalk (0.06%). Flower had THC of 0.56%, while other fractions were less than the 0.3% legal threshold. Similarly, total cannabidiol (CBD) ranged from 0.05-11.4% with the greatest concentrations in the flower and least in the stalk. Our results indicate there is potential for hemp to be integrated into cattle production, especially the leaves. Despite adequate nutritional value, there are practical limitations with feeding hemp flower to cattle. In-vivo trials are needed to assess digestibility and profile cannabinoid metabolism in various tissues before hemp can be integrated into cattle diets.