Cows fed hemp silage high in tetrahydrocannabinol (THC) produced contaminated milk and showed signs of intoxication in a study that has garnered attention for making cows “get high” on hemp. But the study also showed that other forms of hemp silage did not have the same effect, suggesting concentrations of cannabinoids like THC will be critical to determining which hemp products should be approved for use in animal feed. In the study, led by researchers at the German Federal Institute for Risk Assessment, lactating dairy cows initially received a diet in which corn silage was partially replaced by a hemp silage made from the whole hemp plant. The initial silage was intentionally selected to contain lower concentrations of THC in order to provide the cows with an “adaptation” period, according to the researchers.

After this adaptation period, the researchers switched the cows to a diet containing hemp silage comprised exclusively of the leaves, flowers and seeds of the hemp plant. This silage intentionally contained a higher concentration of of THC, the cannabinoid known to be responsible for most of the intoxicating effects associated with cannabis, with the researchers estimating that the cows ingested up to 86 times more THC than would be required to trigger negative health effects in humans. Cows developed symptoms including increased salivation and nasal secretion after they began eating the high-THC diet. The study also observed that feed intake, and therefore milk production, decreased significantly two days after the high-THC silage was administered. These symptoms abated after the high-THC diet was removed, according to the researchers, and did not occur during the initial adaptation period. Researchers also observed that the milk from the cows in the study contained detectable levels of multiple cannabinoids, including THC, during the adaptation period where the cows received the low-THC hemp, and when they were fed the high-THC hemp. The amount of THC that accumulated in the milk exceeded the acute reference dose at which negative health effects may occur in humans. However, the researchers noted that the acute reference dose is a hypothetical limit and that the study did not test whether the milk had any actual effect on humans. The results of the study indicate that “livestock farmers should only feed components of commercial hemp plants that are approved as feed or components of feed,” said the spokesperson for the German Federal Institute for Risk Management.

Dairy farmers are now receiving somatic cell count and clinical mastitis results after each milking through the Mastitis Pattern Analysis Tool (MPAT). The MPAT analyses individual herd data to determine whether the predominant infection patterns is environmental or infectious during the lactation or dry period, as well as the seasonality of infection and heifer infection.

This will allow farmers and veterinarians to work together to identify the pattern of mastitis in their herd and to take the most effective targeted control measures. The stakes are high, as mastitis causes greater economic losses than any other disease affecting dairy cattle production. Speaking about the tool, which was developed at the University of Nottingham with the help of a research team from the Agricultural and Horticultural Development Board (AHDB) and with significant government funding, Jake Thompson, from LLM Farm Vets, part of the VetPartners group, said:

“The great thing about this tool is that both the farmer and myself are sent a report automatically after each milk recording. It allows us to have a targeted conversation about udder health as soon as we have their latest data available. If the mastitis pattern shows there is more of a problem in early lactation from infections picked up from the environment during the dry period, we will then look more closely at how the dry cows are being managed. On other farms, the main current problem may be completely different.”

Genetics company Semex UK believes it can reduce methane emissions by 20-30% by 2050 through breeding cows with lower methane emissions. The company is working with Canadian dairy testing and genetic evaluation company Lactanet and the University of Guelph to find a genetic solution to reduce methane emissions.

Over the past 5 years, Canadian milk-recording organisations have taken mid-infrared (MIR) spectroscopy records of more than 13 million milk samples, of which 700,000 have been analysed by Lactanet geneticists to predict methane emissions from cows tested across Canada.
The results showed that genetic selection can significantly reduce methane emissions. Scientists found an 85% correlation between actually collected methane and predicted methane emissions based on genetics, concluding that there is a genetic way to reduce methane. This is because the genetics of the cow also affect methane production in the rumen, as well as the microbes.

This genetic trait is 23% heritable, which is comparable to production and immune response with 70-80% reliability with no impact on yields or fat and protein levels. Dr Michael Lohuis, Semex vice president of Research and Innovation, said: “We already knew that genetics has a big role to play in reducing output, as it is the main way dairy farmers can produce more product with less input and less output. But this technology takes the role of genetics to a higher level.” He claimed at Semex’s annual conference in Glasgow that methane production from cows could be reduced by 20-30% by 2050, depending on the intensity of selection.