Hemp is moving from the field to the feed trough. The science that should guide the move is lagging behind. Before 2014, US hemp acreage stood at zero. By 2020 it had climbed to a peak of around 400,000 acres. Regulators have now taken the first steps towards letting the crop into animal feed. That makes hemp in the food chain a live question for farmers, regulators and every family that buys milk.
This report on hemp in the food chain draws on peer reviewed studies, regulatory documents and press coverage published between 1990 and 2024. The picture is uneven. Some findings are solid and some are anecdote. One industry claim has no published evidence behind it. Still, the strongest studies agree on a key point. Cannabinoids can travel from feed into an animal’s blood and, in dairy animals, into milk.
The Feed Market Opens Its Doors
In January 2024 the Hemp Feed Coalition announced a milestone. Hemp seed meal for laying hens had won a recommendation from the US Food and Drug Administration’s Center for Veterinary Medicine. The Association of American Feed Control Officials then voted the ingredient into its Ingredient Definition Committee, the final step on the approval pathway. According to Margy Eckelkamp’s report for AgWeb, the definition allows hemp seed meal at up to 20 per cent of a laying hen feed mix. It is the first hemp feed ingredient to get that far, which puts hemp in animal feed on a federal track.
The industry sees an opening. Wendy Mosher, vice president of the coalition, told AgWeb that a commodity crop needs a feed outlet. The coalition also points to higher omega 3 content in eggs. In February 2024 the Minnesota Star Tribune reported that the approval gives growers access to part of the $85 billion US livestock feed market. Meanwhile, John Strohfus, founder of Minnesota Hemp Farms, said livestock feed gives growers “a floor”. He expects other species to follow. Horses, which do not enter the food supply, look like an early target.
One claim about hemp in the food chain deserves scrutiny. The coalition says it has been verified that potential cannabinoid contaminants do not transfer into the egg product. AgWeb does not name the study behind that statement. None of the research examined for this report tests eggs. For now, the claim stands as an industry assertion rather than a published finding.
A German Dairy Trial Puts Hemp in the Food Chain to the Test
The most detailed test of hemp in animal feed comes from the German Federal Institute for Risk Assessment in Berlin. Bettina Wagner and colleagues published their paper in Nature Food in November 2022. They followed ten lactating Holstein Friesian dairy cows. One cow left early with lameness. Another developed a metabolic disease and was excluded from the statistics. The analysis therefore covered eight animals.
Four stages made up the trial. A hemp free control week came first, then a week of adaptation on silage with very low cannabinoid content. Six days of exposure followed, and eight days of depuration ended the trial. During exposure, one group ate 0.84 kilograms of dry matter a day. The other group ate 1.68 kilograms. Both portions came from the leaves, flowers and seeds of a Finola hemp variety. That variety still sat below 0.2 per cent THC, the limit the paper cites for industrial hemp in the European Union.
What the Cows Showed
The cows reacted anyway. From the second day of exposure, feed intake and milk yield fell significantly in both groups. Heart and respiratory rates dropped, and in some animals they fell below normal reference values. The team also recorded pronounced tongue play, more yawning, heavy salivation, nasal secretions and a drowsy look. Some cows in the high dose group walked with an unsteady gait. Every change faded within two days after the researchers stopped feeding hemp.
By the authors’ calculation, the cows took in up to 86 times the lowest dose at which THC has caused adverse effects in humans. The team could not say which cannabinoid caused the reaction. THC is the most likely cause, they wrote. Combined effects, other plant compounds and a change in diet could also play a part. Their conclusion is direct. Nobody can judge hemp in the food chain harmless without first analysing its cannabinoid content.
How Much Reaches the Milk Jug
The bigger question for hemp in the food chain is what ends up in the milk. In percentage terms the transfer looks small. THC moved from feed into milk at a rate of 0.20 per cent, and CBD at 0.11 per cent. The THC rate is 33 to 100 per cent higher than earlier experiments reported. However, the cows ate so much silage that the numbers still added up. Milk from the exposure period held up to 316 micrograms of THC and 1,174 micrograms of CBD per kilogram.
Meanwhile, the milk concentrated the compounds. At the end of exposure, milk levels ran 6 to 26 times higher than blood plasma levels for THC. For CBD the gap was 11 to 32 times. The authors read this as a sign that both compounds accumulate in milk. Even after eight days without hemp, milk from the high dose group still carried 5.0 micrograms of THC and 16.2 micrograms of CBD per kilogram.
Measuring Milk Against the Safety Limit
Next, the researchers compared those levels with the European Food Safety Authority’s acute reference dose for THC. That dose is one microgram per kilogram of body weight over 24 hours. Using European food consumption data, they found the dose exceeded in several consumer groups. Average consumption of milk and dairy from the lower dose group pushed people under 18 up to 14 times over the limit. Heavy consumers went up to 57 times over. Milk from the higher dose group topped the limit by up to 120 times across all population groups. Even milk from the adaptation week put high consuming infants 1.5 times over, although that silage held very little cannabinoid.
Some caution is fair when weighing hemp in the food chain. The authors call their assessment cursory. It rests on eight cows, six days of exposure and the assumption that every glass of milk carries the measured level. On the other side, THCA in milk could convert into THC during processing, the paper notes. Ultra high temperature treatment is one example, and it could add to exposure. For CBD, which reached higher levels in milk than THC, the data are too thin to judge health risks at all.
Why Children Sit at the Centre of the Concern
The German tables put infants and toddlers at the top of every risk column for hemp in the food chain. An older study points the same way. In 1990, Gulzar Ahmad and Naeem Ahmad reported in the Journal of Toxicology: Clinical Toxicology on buffalo in northern Pakistan. The animals graze among wild cannabis. During June and July, 60 per cent of those tested had detectable THC COOH, a THC metabolite, in their urine. Half of those animals produced milk contaminated with THC or its metabolites.
The result for children is hard to ignore. Among children aged six months to three years who drank that milk, 29 per cent had low levels of the metabolite in their urine. The authors called passive consumption through dairy a serious problem where cannabis grows unrestricted. Children, they warned, are exposed more than adults. The pair judged the issue unlikely to be serious in the United States but one that “could be a problem in the future”. Hemp in the food chain makes that warning worth revisiting.
Children meet hemp products in other ways too. A JAMA paper quoted in a November 2022 commentary counted 2,362 reports of delta 8 THC exposure to US poison control centres. The reports ran from January 2021 to February 2022. About 40 per cent involved accidental exposure, and the paper puts that figure at 82 per cent among youth. Seventy per cent of cases needed evaluation at a health facility. Eight per cent went to critical care, and one child died. Animal poison centres also reported more accidental pet exposure.
The Kansas Calves and the Missing Meat Data
In 2020 Kansas State University researchers led by Michael Kleinhenz tested what happens after a single dose. Eight Holstein calves swallowed about 35 grams of industrial hemp flower in capsules. The team then sampled blood for 96 hours. Acidic cannabinoids, above all cannabidiolic acid or CBDA, passed readily from the rumen into the blood. CBDA peaked at a geometric mean of 72.7 nanograms per millilitre after around 12 hours. Its half life was 14.1 hours.
Other acidic cannabinoids also appeared. THCA A, CBCA and CBDVA showed up in every calf. THC itself did not appear in any blood sample, and CBD turned up in only four samples from two calves. The calves showed no adverse effects. Wagner’s team put the difference in THC detection down to dose, since the German cows ate hemp silage every day for six days.
The Kansas authors pointed to a practical gap instead. As the paper notes, the FDA has stated that cannabinoids count as adulterants in food producing species. Vets therefore need half life data to set withdrawal intervals, meaning the wait before an exposed animal can enter the food supply. Yet the paper says no published data described cannabinoid residues in edible tissue. None of the later work reviewed here fills that gap. For hemp in animal feed, meat remains the largest blind spot.
Pot Pigs and the Problem With Anecdote
Some of the loudest claims about cannabis and livestock come from stunts rather than studies. In 2013 the Associated Press reported on a Washington state farmer and a Seattle butcher. They fed three Berkshire pigs ground roots and stems from a medical marijuana dispensary. The butcher sold bacon at $17 a pound and chops at $16.90 at Pike Place Market. Both men said the meat cannot get anyone high and called it a flavour experiment.
John McNamara, an animal scientist at Washington State University, was unimpressed. He called it the dumbest thing he had seen in more than 37 years. Any drug added to food animal feed, he said, needs federal sign off after extensive review. Research, he added, has shown that ingested cannabis can transfer into tissues.
In 2016 a cannabis focused website, Green Rush Daily, repackaged the story. Its headline claimed marijuana fed pigs are bigger and tastier. The site said four pigs fed potent trimmings for four months gained 20 to 30 pounds more than half a dozen others. It also floated feeding cannabis to chickens and cows in place of antibiotics and hormones. That account offers no independent measurement. It also clashes with the AP report, where the farmer said he could see no effect on his pigs. Neither report describes any testing of the meat.
Switzerland Drew a Line in 2005
Some regulators have not waited for proof on hemp in the food chain. On 1 March 2005 Switzerland banned all hemp as livestock fodder over fears of THC in milk. Federal Agriculture Office spokesman Jürg Jordi said the office did not want THC in milk “because milk is a natural product”. The issue surfaced after a company called SanaSativa advertised that hemp improved milk quality. It is said to have around 60 Swiss farmers on its books. Agroscope, the federal research station, found traces of THC in milk. Researcher Daniel Guidon pointed to the Pakistani study on children. The Swiss Farmers’ Association welcomed the ban because farmers wanted to preserve the reputation of their milk and cheese.
Critics spoke up as well. Barbara Früh of Bio Suisse called the scientific foundations “lean”. She noted that Agroscope had fed cows THC in pill form rather than hemp fodder. The Pakistani study, she added, involved buffalo eating cannabis, not hemp. Dairy farmer Stefan Selinger called the ban an overreaction and said his cows had grown healthier. Früh added that a correctly carried out experiment finding THC in milk would win her support for a ban. The 2022 German trial did what she asked. It fed real hemp silage and measured the milk directly.
Regulators Face Hemp in the Food Chain Without the Data
Regulators admit the gap. In October 2021 the FDA published its Cannabis Derived Products Data Acceleration Plan. It put the CBD market at an estimated $4.6 billion and forecast it to quadruple by 2026. The plan lists products marketed for animals among the thousands sold as drugs, foods, beverages, cosmetics and supplements. Its central admission is stark. Growth in the market continues to outpace the growth in the science and in understanding of the public health implications. More than 40 per cent of CBD products sell through online channels, where traditional surveillance struggles.
The agency is testing hundreds of hemp products for cannabinoids, toxic elements, pesticides, residual solvents and microbial pathogens. It is also studying the risk of liver injury from CBD. In addition, it reminds industry that developing the safety data is industry’s responsibility. Psychiatrist Albert Stuart Reece, writing in the same November 2022 commentary, argued that cannabinoids should be regulated like other known genotoxins. He works at the University of Western Australia and Edith Cowan University. His view rests on studies of cannabis exposure rather than milk or meat. It sits outside the feed question, yet it shows where the wider debate is heading.
Why Testing and Labelling Add to the Doubt
Testing for hemp in the food chain is itself shaky. An Italian review by Pellegrino Cerino and colleagues in Cannabis and Cannabinoid Research notes that hempseed should not contain cannabinoids. Even so, an analysis of ten commercial organic hempseed oils found THC and CBD at concentrations that were not insignificant. It also found 30 other cannabinoids, probably from seeds contaminated with flower material.
Labels do not help. A study of 88 CBD liquid products from 31 companies found a median CBD level of 9.45 milligrams per millilitre. The median label claim was 15.00. Oral oils carried an inaccurate label in 55 per cent of cases. The reviewers concluded that industry and the scientific community have not independently done the clinical research needed to prove or disprove the safety of hemp derived products.
Another yardstick, the official test for THC in hemp, is under question too. Wagner’s team measured total THC of 65 and 1,317 milligrams per kilogram of dry matter in its two silages. The European Union’s Community method gave 21 and 186. That is roughly three times and seven times lower. The authors question how sensitive the Community method is for finding the true THC content of hemp.
What Hemp in Animal Feed Demands From Regulators
Taken together, the sources point to a short list of jobs that come before hemp in the food chain expands. Feed makers need to analyse cannabinoids in every batch, because the German team found that variety, plant part and harvest time change the level. Regulators need withdrawal intervals built on measured half lives, as the Kansas authors urge. Researchers need to publish tissue residue data for meat and eggs, which would show whether the coalition’s claim holds. Milk safety for infants and toddlers, the group the German tables flag, also needs an answer. So does the open question of CBD.
None of this is a case against hemp as a crop. The Italian review describes hempseed as a valuable source of fatty acids, protein and minerals. But food safety rules exist because the people most exposed cannot check a label or read a lab report. Small children who drink a lot of milk are the clearest example. Until the missing data arrives, the burden of proof belongs with the industry asking to put hemp in the food chain. (Source: WRD News)