Within the first week of giving birth, a high-yield dairy cow can increase milk production to as much as 100 pounds per day, according to assistant professor Johan Osorio of South Dakota State University’s Department of Dairy and Food Science. “This dramatic change causes stress—we are walking a thin line between healthy and unhealthy, particularly in cows that can deliver a high milk production.”
His research focuses on how methionine, an essential amino acid, can improve the health of cows making the transition into lactation. “Providing a good amount of methionine during that transition period can minimize stress,” said Osorio, who came to SDSU in 2016 after doing postdoctoral research at Oregon State University. However, his research goes deeper than that.
“We are breaking it down to the molecular level,” Osorio said. His dissertation research showed that the methionine supplement interacts with the genome, affecting more than 2,600 genes. At SDSU, he is exploring these nutrigenomic interactions through U.S. Department of Agriculture Hatch Act funding from the South Dakota Agricultural Experiment Station.
What he discovers may make it possible to customize the fat and protein makeup of milk to meet consumers’ needs.
Easing stress of transition
“A lot of metabolic adaptations occur in dairy cows during the days leading to calving and during the start of the lactation,” Osorio said. During this stressful time, cows are likely to eat less, which negatively affects their metabolism and immune system and can leave them vulnerable to disease.
His work showed that feed intake and milk quality improved in cows receiving a methionine supplement during the 30 days after calving. “The milk had more fat and protein,” he said. “There was also some indication of better resistance to mastitis.”
When Osorio examined gene markers in the cows’ liver, he found the methionine supplement changes the way in which 2,633 genes in the liver are expressed, either increasing or decreasing the production of specific proteins. Those changes improve liver function, thereby reducing inflammation and stress.
Analyzing protein changes
Osorio and his two doctoral students are using bovine mammary epithelial cells as a model to examine the molecular changes that methionine triggers which, in turn, affect milk production and improve the animal’s overall health. The researchers examine RNA, a single-stranded molecule that transcribes or code, the information for amino acids that are the building blocks to produce a protein. When animals consume a methionine supplement, the production of specific types of proteins can be turned on or off.
To track those changes, Osorio uses a system developed at the Massachusetts Institute of Technology in which two key proteins are tagged with different fluorescent colors. That then allows the researchers to microscopically track what’s happening when varying levels of methionine are added to the cell cultures.
“If we increase the methionine in the media, the cells respond,” he explained. “We are building a model in the lab that we can then test on the farm.” Initial testing confirmed that increasing the levels of methionine can impact the signaling of the proteins, but since the effect is not dose-dependent, other factors are likely at work.
“We are able to control the carbon dioxide, temperature and humidity of the cell during our experiment and can take photos at regular intervals to track protein activity in real-time in the cells,” he explained. Now the researchers are using software to gather quantitative data from each cell based on the fluorescent intensity. The next step will be to analyze blood samples from an animal study in which cows were given varying levels of methionine.
“If you go deep down, you might find key regulatory mechanisms that can be enhanced,” he said. “That is part of the excitement, not knowing what you are going to find.”