If you love the flavor and mouthfeel of Penn State Berkey Creamery ice cream, you can thank, in part, the milk fat. You also can thank research on the diet of dairy cows, which began before the creamery's founding 150 years ago.

As the Penn State landmark celebrates its sesquicentennial this year, College of Agricultural Sciences researchers continue to investigate, among other things, how dairy cows' rations can be adjusted to produce milk with a higher fat content.

These milk fat studies are important because Americans are drinking less fluid milk than they used to but are consuming more products made from milk fat, such as cheese, butter and -- you guessed it -- ice cream. This change in demand is neatly encompassed by the creamery's "cow to cone" ethos for ice cream, and milk fat is a major reason why it tastes so rich and creamy.

"Animal scientists have been studying how various feed rations fed to dairy cows affect the milk they produce for longer than Penn State's creamery has existed," said Kevin Harvatine, associate professor of nutritional physiology. "With the growing demand for milk fat, we are experimenting with novel feed supplements to boost the fat content of milk."

Harvatine, whose research is focused on improving dairy efficiency through nutrition, with specific interest in regulation of milk fat synthesis, noted that trying to manipulate milk fat with feed rations is a balancing act for dairy producers. High-producing cows need rations that keep them healthy and provide the energy to produce lots of milk, but these can lead to lower levels of fat in milk.

"Milk fat is an economic issue for dairy producers -- they get paid a premium for milk with higher fat content," Harvatine said.

"We have known about a phenomenon called milk fat depression for a long time, but we are breeding for higher milk production, and producers are faced with the challenge of feeding cows that make a large amount of milk," he said. "So the way we meet these high energy needs is to feed more grain that has higher digestibility than forage -- but we know that can cause milk fat depression. My research is gauging the effect of certain diets and diet supplements on high-producing cows, and their influence on milk fat."

On average, dairy cows are fed 50 to 55 percent forage, and most of the remainder of their diet is typically corn grain. Usually, high-producing cows also are given a protein supplement, such as soybean and canola meal, or distiller grains, Harvatine said.

"Depending on the region, we also feed a lot of unique byproducts to dairy cows, such as cookie and candy meal that comes from broken cookies and stale materials that are ground-up and mixed together and put into animal feed. Some producers add some very specific supplements, such as amino acids."

The cow's rumen -- the large fermentation chamber of its stomach -- is the regulating factor in trying to boost milk fat, Harvatine said. Some things that increase diet energy density, such as starch-rich grains and certain oils, disrupt the microbe community in the rumen, suppressing the fermentation process that allows cows to digest their feed.

"Microbes don't like oil," Harvatine explained. "That's why you can let your cooking oil sit out at room temperature and bacteria won't grow in it. It is a similar situation in a cow's rumen. Unsaturated oils disrupt the microbe community and change what the microbes produce, resulting in unhealthy animals and lower milk production."

Seven years ago, when Harvatine joined the Penn State faculty, the first research he conducted was a time-course experiment to determine how long it took for a cow to get milk fat depression, and once she had the malady, "and you are rescuing her," how long it took the animal to recover.

"That really has been the key to designing experiments to see a cow's response to dietary changes," he said. "Dairy nutritionists now know that if they make changes in a cow's diet, reciprocal changes in milk fat content should show up in seven to 10 days, if they are going to show up at all."

The last two summers, Harvatine presented to the joint annual meeting of the American Dairy Science Association and American Society of Animal Science promising results from studies investigating the effect of a feed supplement called Alimet, developed by Novus International, on milk fat. And in 2014, he published research in the Journal of Dairy Science related to supplementing dairy cattle's diet with palmitic acid.

With the growth of the palm biofuel industry in recent years, byproducts from palm oil processing have been added to animal feeds, leading to speculation that a palmitic acid supplement would increase milk fat. So Harvatine conducted a number of experiments at the Penn State dairy barns to find out.

"What we found is that palmitic acid supplements can increase milk fat a little bit by providing more fat for the mammary to make milk fat," he said. "It seems that palmitic acid is metabolized by the mammary gland differently than the fatty acids that we find in most other plant oils."

Because consumers continue to crave products rich in milk fat, such as Penn State Berkey Creamery ice cream, researchers will discover ways to influence cows to produce milk with a higher fat content, Harvatine predicted. But it will take some time.