One of dairy farmers' biggest concerns is the vulnerable and important period for the dairy cow that extends three weeks before and three weeks after calving. Her metabolic needs increase dramatically, and how she copes with this high-energy transition period influences how well she performs during the rest of the lactation, according to The Pennsylvania State University.

During this transition cow period, diseases can result in milk yield decreases of 5-10 lb. per day at peak lactation -- a considerable economic loss for the producer. Research has shown that there is a domino effect: When a cow suffers from one transition disease, she is more likely to develop another, such as mastitis, ketosis or postpartum metritis.

Field surveys done by Penn State Extension show that more than 50% of cows will experience one or more metabolic or infectious diseases following calving.

So, dairy nutrition researchers, including Alex Hristov at Penn State, have been experimenting with various dietary supplements to bolster the immune systems of transition cows. Hristov, a professor of dairy nutrition in the College of Agricultural Sciences, has concentrated on the effects of spicing up the diets of transition cows -- feeding them phytonutrients and essential oils that are known to boost and support the immune systems of other species, including humans -- and gauging the cows' health response.

Phytonutrients and essential oils -- bioactive compounds that act as antimicrobials and antiseptics -- are not required by dairy animals, but ingesting the compounds could make cows healthier, according to Hristov. Some examples are allicin from garlic, thymol from thyme and oregano, capsaicin from hot peppers, eugenol from cloves, pinene from juniper berries, limonene from dill, cinnamonaldehyde from cinnamon and curcumin from turmeric.

At first, Hristov and other animal scientists considered phytonutrients and essential oils as a way to improve or alter rumen fermentation with naturally occurring compounds rather than commercial additives or antibiotics. The objective in altering rumen fermentation is to reduce methane gas production and increase propionate and butyrate production, resulting in more efficient fermentation and reducing greenhouse gas emissions.

However, in recent research, Hristov has been looking beyond the rumen. In a series of papers, including an invited review published this spring in the Journal of Dairy Science, he and postdoctoral scholar Joonpyo Oh focused on the intestinal effects of phytonutrients in dairy cows, especially capsicum oleoresin from chili peppers.

Oh, who conducted the research as part of his doctoral thesis, concluded that phytonutrients appear to have positive physiological effects on the immune response in ruminants -- lactating dairy cows in particular.

"The novel thing about this research is that we have shown that these phytonutrients can have downstream effects after the rumen," Hristov said. "For the first time, we have shown that these compounds can bypass the rumen, which means they can avoid microbial degradation in the rumen. So, they can be absorbed -- through specific receptors -- in the small intestine, which allows the cow to benefit from their physiological effects, including improvements in immunity, oxidative stress and insulin regulation."

He explained that the regulatory effects of phytonutrients on "cytokines, acute-phase proteins, blood immune cells and oxidative stress status, including lipid peroxidation and endogenous antioxidants," seem to be beneficial for immune suppression of inflammation disease in dairy cows.

Although more research is needed to confirm results of Penn State studies, Hristov said he believes phytonutrient supplements such as capsicum oleoresin in the feed of transition dairy cows could have an effect on the dairy industry.

"The transition period is the most critical period in the life of a cow, so anything that can decrease metabolic diseases during that time could prove to be significant," he said. "Anything that improves animal health and immune response in these cows is important, and in previous studies, we even saw an increase in milk production. That kind of direct impact, if proven, would be very important."

Follow-on studies are unfolding in Hristov's lab in collaboration with a Swiss company to develop a rumen-protected capsicum product to reliably deliver the benefits of phytonutrients to cows' immune systems. Researchers are using capsicum oleoresin, Hristov noted, because after investigating other phytonutrient compounds, the peppers had "the most pronounced effect on cows' health."

Do cows like having their diet spiced up? "From the several experiments we conducted, they don't seem to mind it," Hristov said. "Cows consumed the 'spicy' diet the same as the control diet. Perhaps, like some of us, they like it."