Industrial hemp was outlawed in the USA in 1937 under the Marihuana Tax Bill along with all other varieties of cannabis. Prior to this, it was widely grown for industrial and agricultural purposes across the world and was thought to have arrived in America via the British who grew the crop wherever they went to enable them to supply their naval fleet with hemp rope.

In 2018 the US legalised hemp again under the Farm Bill. The introduction of the new bill resulted in a flurry of research for uses such as biofuel, human therapeutics and fibre for plastics and hempcrete.

In a recent study researchers at Kansas State University found that feeding industrial hemp to cows can have a positive effect on their welfare by reducing stress and increasing the amount of time they spend lying down. 

In examining the safety and efficacy of industrial hemp researchers had to investigate “the pharmacokinetics and potential biological effects of cattle exposed to repeated doses of industrial hemp”. They also dampened fears that feeding cattle industrial hemp would lead to an accumulation of cannabinoids in the animals that may be passed on to humans through the food chain. 

Michael Kleinhenz, assistant professor of beef production medicine at the K-State College of Veterinary Medicine who led the research said in a press release, “Our new research helps us better understand how cannabinoids present in industrial hemp interact with bovine physiology and pharmacology. For instance, we now know that repeated daily doses of CBDA via feeding hemp does not result in accumulation of cannabinoids in the blood. Additionally, it solidified previous research and shows that each cannabinoid has its own absorption and elimination profile.”

The lying behaviour of cows is something that is closely studied due to its suspected link to increased welfare. Previous studies investigating cow lying behaviour have suggested that a decrease in lying time could result in an increase in ailments such as lameness and hoof lesions, and could result in changes to the endocrine system which leads to more stress. There have also been suggestions that a decrease in lying time can result in a decrease in milk production in dairy cows, although more evidence is needed to support this claim. It has been determined however that time spent lying increases cow saliva production which enables them to chew their food more, which in turn aids digestion. 

To carry out the study researchers selected 16 male Holstein cows who were split into two groups of eight. One of the groups was fed 25 grams of hemp mixed with 200 grams of grain, with a target hemp dose of 5.5 milligrams per kilo of bodyweight of cannabidiolic acid (CBDA), the other group were the control group and was fed only grain. 

To assess the stress levels of the cows their behaviour was monitored with a machine called an accelerometer. Accelerometers are tools used to measure accurately movement and behaviour in animals. Researchers also took samples of blood and plasma from certain areas of the cows for analysis. 

The results of their study and analysis show that feeding cows with industrial hemp containing a high concentration of CBDA for a period of 14 days increases lying behaviour and leads to a decrease in the biomarkers of stress and inflammation.

“Our most recent data shows how cannabinoids via industrial hemp decreased the stress hormone cortisol as well as the inflammatory biomarker prostaglandin E2,” Kleinhenz said. “This shows that hemp containing cannabidiolic acid, or CBDA, may decrease stress and inflammation in cattle. Thus, hemp may be a natural way to decrease stress and inflammation related to production practices such as transportation and weaning.”

The size of the study, 16 cows, and the length of the study, 14 days, suggest that more investigations need to be carried out before any strong conclusions can be drawn.  

“Further work is needed to determine if cannabinoids can alter the stress response in cattle during stressful times such as transportation and weaning, but we hope this research is a step forward in the right direction,” said Kleinhenz.

The research was funded via a grant from the Agriculture and Food Research Initiative of the U.S. Department of Agriculture’s National Institute of Food and Agriculture.

Adding hemp into feed reduces stress in cows

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