In recent years the production of hemp has increased due to changes in federal regulations on its medical use. Growing hemp has many challenges, but if you or others in your area are growing hemp for cannabidiol (CBD) or fiber, there is likely a large amount of biomass remaining. Hemp can produce 15,000 to 20,000 pounds of dry yield per acre.
Different parts of the hemp plant vary widely in nutritive value. Crude protein for the stalk, leaves, and whole plant are reported recently as 5.3, 13.0, and 6.9%, respectively. Fiber fractions of the stalk, leaves, and whole plant were 84, 45, and 82% for neutral detergent fiber (NDF), and 65, 21, and 61% for acid detergent fiber (ADF), respectively (https://doi.org/10.15232/aas.2020-02018). The high fiber and low protein for the stalk indicates the likelihood of poor digestibility but the low fiber and high protein for leaves indicates high digestibility. A recent study found that the digestibility of the stalks was only 21% whereas the digestibility of the leaves was 93% and the whole plant was 67% (https://doi.org/10.1093/jas/skae019.028).
During the processing of the hemp plants, several by-products can be produced such as straight seed, dehulled seed, seed cake, seed meal, stalk, and seed hulls. The nutritive value of these can be seen in Figure 1. The seed and seed byproducts have high crude protein values similar to typical feedstuffs used in cattle diets such as soybean meal, cottonseed meal, and distillers grains. Byproducts from the stalk are of generally low quality similar to cottonseed hulls and wheat straw, and byproducts from the seed hulls are of intermediate nutritive value similar to soybean hulls. There is high variability in reported values. The crude protein ranged from 30 to 50% for seed meal and 19 to 28% for seed. The NDF ranged from 54 to 70%, and the ADF ranged from 44 to 54% for seed hulls. Thus, analysis of the batch to be used should be completed prior to formulating the diet.
Even though the hemp plant and byproducts from the use of hemp for human uses are of good nutritional value, legal restrictions prevent the use of hemp and its byproducts in livestock feed. There is currently little data available on the amount of cannabinoids (e.g., CBD and THC) in meat, milk, and eggs from livestock fed hemp. Additionally, there is minimal data on the effects of cannabinoids on animal health and welfare. However, research is investigating these effects and if approved, hemp and its byproducts could be valuable feedstuffs for cattle production.
