WESTERN PRODUCER — Methane produced in the rumen of cattle during digestion is a potent greenhouse gas.
Japan’s agricultural industry produced 29.3 million tonnes of greenhouse gas emissions in 2020, accounting for 2.8 percent of the country’s total emissions. A quarter of that came from enteric fermentation within livestock.
For years, researchers have been exploring feed additives and feed management systems to reduce methane emissions. Now, a collaborative project has been undertaken by scientists at Tohoku University in Sendai, Japan, and colleagues at Hyogo Prefectural Technology Center of Agriculture, Forestry and Fisheries.
They employed biomarkers to study the metabolic characteristics of Japanese Black cattle to learn more about the nutritional characteristics linked to enteric methane emissions.
Working with 21 steers aged 12 months at the outset of the study, they examined the physiological parameters of blood metabolites, hormones, amino acids, rumen fermentation, and liver transcriptomes to define the relationship between methane emissions and the cattle’s metabolism and nutrition. The Japanese Black cattle breed was chosen given Japan’s unique feed management system.
Farmers who raise Japanese Black cattle use a feeding system that focuses on fattening cattle during 11 to 30 months of age to induce greater accumulation of intramuscular fat.
“During the fattening period, the cattle are fed a high-energy diet with low levels of roughage until slaughter at 28-30 months of age,” said professor Sanggun Roh with Tohoku University’s Graduate School of Agricultural Science. “During the final stage, total feeding consumption during fattening is typically four to five kilograms per day and more than 90 percent of the concentrate is used.
“Japanese cattle farmers have also used the regulation of blood vitamin A levels during the fattening period as another strategy to improve beef marbling. As such, Japanese Black cattle are raised in a unique feeding management system so we thought that the physiological characteristics related to methane emissions might be different from other species.”
The experimental animals were fed concentrate and roughage consisting of rice straw and kraft pulp feed twice daily with free access to water. Feeding regimes were divided into early, middle and late fattening phases. All the steers were fed with specific amounts of the formula diet that were changed during each of the three fattening periods.
“Our study analyzed a variety of physiological parameters collected from blood, rumen fluid, tissues, etc. to reveal the characteristics related to methane production,” he said. “Especially, blood metabolites have been used for feeding management of cattle as an indicator of nutritional metabolic status. Glucose, NEFA (non-esterified fatty acids), ketones (chemicals made in the liver) and cholesterol are indicators that reflect the energy intake and energy balance of cows, and it is possible to determine whether the current feeding management is appropriate. Total protein and albumin concentrations in blood and blood urea nitrogen levels can vary depending on the protein level of the diet and the metabolic and pathological status of the cattle.”
In addition, the blood levels of liver-derived enzymes were analyzed to evaluate liver function and any possible disease. Roh said that hormones such as insulin, insulin-like growth factor 1 (IGF-1) and cortisol can be used as indicators of metabolism or disease in cattle feed management.
“Another important parameter, ruminal volatile fatty acids (VFA), are a major source of energy for ruminants,” said Roh. “Acetate, propionate, and butyrate are the key VFAs formed during rumen fermentation and the composition of VFAs changes depending on dietary and physiological conditions. In general, high-starch, concentrate-based diets are associated with propionate production, whereas forage-based diets containing large amounts of cellulose are related to acetate production.”
The study did not cover whether there was a difference in the amount of methane emission based on the genetic background of each individual animal.
“However, considering that there was a bias by sires (21 cattle in the study were born from just two sires), when grouping them into high-methane emission cattle (HME) and low-methane emission cattle (LME), the genetic background may have a significant impact on the amount of methane emission in individual cattle. We are currently reviewing this.”
Roh said that methane production is known to be affected by the ruminal metabolic state. The ruminal production of propionate, one of the volatile fatty acids produced by the digestive process, reduces methane production by consuming hydrogen.
“Our data also showed a low propionate rate in high methane emission cattle,” he said. “Contrary to this, blood amino acid levels are thought to be a case in which methane emission levels affect the physiological condition of cattle. In our study, most blood amino acid levels were found to be lower in high methane emission cattle, suggesting that there were differences in amino acid metabolism depending on methane emission levels. We interpret the difference in amino acid levels as a reaction to energy loss caused by methane production. Thus, methane production and its physiological conditions seem to be interacting with each other.”
He said that the findings suggest that the physiological differences and liver transcriptomes of cattle can be used to monitor the levels of methane emissions from Japanese Black steers and other similar cattle breeds.
“The association between various physiological parameters and methane emissions may provide a new perspective that lays the groundwork for further research into methane reduction strategies.”
The research has received interest from local farmers who provided some feedback to the research team. They expressed interest in reducing methane emissions based on a feeding system and its management and they are looking for greater clarity on how to modify feeding practices to achieve maximum methane emissions reductions.
The study showed that Japanese Black cattle have different physiological characteristics based on their enteric methane emissions. Cattle with high methane emissions actively used amino acids to replenish the energy lost during methane production, thus decreasing blood amine acid levels and increasing blood insulin concentration without changing the growth and productivity of cattle.
Roh said in the report that their results suggest that physiological differences and liver transcriptome could be used as parameters to monitor the levels of methane emissions from Japanese Black steers and other similar cattle breeds.
“Accordingly, the relationship revealed in this study between the various physiological parameters and methane emissions might provide a new perspective different from the existing methane reduction studies.”
The research was published recently in the journal Scientific Reports.
