Feeding recreational hemp residues: A win-win opportunity for the animal, the consumer and the environment?

I met Dr. Mike Ruckle while we were Postdocs of the COOP Research Program. He conducted a project about red clover, while I was doing research on poultry. As our careers went on, we kept in touch. Dr. Ruckle is now working for Puregene AG part of the Pure Holding Group, which is currently the most established hemp breeding and production company in Switzerland. While discussing his work, he once joked about producing meat with hemp flavour and capitalizing on hemp`s huge potential as a forage crop. As a spoilsport, I answered him feeding hemp to farm animals was forbidden, so we should start first by advancing the legalization process. That is when I discovered feeding hemp residuals from recreational hemp production was everything but a silly idea.

Background

The cultivation of recreational (or pharmaceutical) hemp is expanding worldwide for its content in cannabinoids. After extraction of its valuable active substances, the hemp plant still contains a great quantity of proteins and carbohydrates of food-grade quality, often even of organic quality. To date, due to the lack of more interesting value chains, the hemp residue is discarded as green waste such as compost. In times where food waste is no longer acceptable and the demand for animal protein is increasing, upcycling the hemp residue as feed for farm animals offers great opportunities. Yet, this practice is forbidden for public health reasons. Although hemp residues contain very low concentrations of residual cannabinoids and the transfer rate from feed to animal products is therefore likely low, legislation currently rests on the precautionary principle.

Our project

The pilot project investigated the feasibility of feeding hemp residues to farm animals with regards to its palatability and its effects on performance and food safety. With this purpose, we examined the consumer products of chickens. Laying hens were considered an ideal animal model at this stage, due to their simple digestive tract (as opposed to ruminants) and given the fact that they deliver both, meat and eggs. The experimental hemp residues were obtained from Pure Production AG (Zeiningen) as a waste product from their production of medicinal and recreation CBD products. A special authorisation for research purposes was obtained from Agroscope to feed the hemp to laying hens. Another requirement was that both, the hens and their eggs would not be consumed but discarded following the experiment for food safety reasons.

One third of the hens received the hemp residues starting with only 1% and progressively going up to 15% of their regular feed for several days. Another third of the hens received the feed supplemented with the same proportion of alfalfa instead of hemp and the final third received solely the commercial laying hen feed without any supplement.

Preliminary results

Hens are usually very sensitive to dietary changes but the feed containing hemp was very well accepted. All hens remained healthy and produced the same quantity of eggs independently of the feed they received (containing hemp residues, alfalfa or neither). The only noted difference when feeding hemp residues was related to the colour of the egg yolk. The egg yolk of the hens receiving 15% hemp residues in their feed was a little darker and had a more intense red colour than that of the hens receiving the regular feed. A similar change of color to a slight darker color was also noted for the egg yolks of the chickens receiving the alfalfa. Both, hemp residues and alfalfa contain carotenoids which act as natural colorants. Therefore, hemp residues are also suitable as a natural colorant for the egg yolk. An intense colour is usually very appreciated by the consumer, and a reddish component in addition to the yellow colorants is very important for the overall impression of yolk colour.

Still to come

The analyses of the transfer of residues of cannabinoids from the feed to the eggs and to the meat of the laying hens is still ongoing. In this context, the lack of routine methods for the analysis for these substances in animal material presents a real challenge. We are therefore collaborating with the German Federal Institute for Risk Assessment where a comparable study with the milk of dairy cows has recently been conducted. Moreover, blood samples from our hens were also sent to the forensic laboratory of the University of Zurich which has established methods for drug detection in human blood.

Anecdote

The quite strong and unmistakeable smell of hemp was easily recognised by our colleagues entering the storage rooms and immediately put a smile on their faces. However, besides their first comic reaction, the project raised a lot of interest and curiosity among them. Although the raw hemp residues smell quite strong, the smell in the feed is very subtle and we did not notice any comparable smell in the eggs or the meat. However, there was a slight change of smell in the faeces.

After this pilot study, what’s next?

Further studies on larger flocks, over longer periods of time and on other farm animals will be necessary to convince policy makers to allow feeding hemp residues. If so, hemp could present a valuable alternative to imported grain and soy feed. Furthermore, recent claims about health promoting and stress reducing substances in hemp may even raise the interest of feeding hemp to farm animals. However, this would need further investigation. In the end, the production of recreational hemp could have positive outcomes for the environment, the animal, and the consumer.

ABOUT THE AUTHOR

Isabelle Gangnat is a senior scientist in the group of Animal Nutrition at the ETH. A few years ago, she conducted her Postdoc within the COOP Research Program on dual-purpose chicken (INDUCE). Her research interests cover animal physiology, quality of animal products and feed-no-food systems. Probably due to her French nationality, durably produced, local and tasty animal-sourced foods are a motivation for her.