April 27, 2010

The Scientist: Thomas Overton

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An old proverb declares, “I don’t care how many pails of milk I lose, as long as I don’t lose the cow.”  However, “I” also must ensure the continued welfare of “the cow” in order to receive milk.

The health and well-being of a dairy cow determines its production, and today, the average dairy cow in the US produces over 20,000 pounds of milk annually. This high production brings associated and non-associated metabolic conditions under scrutiny in the industry.

Prof. Thomas Overton, animal science, works to improve dairy cattle performance by identifying relevant health risks in real-world settings. His outreach to farmers improves dairy facilities and management strategies.

Overton bears his roots in dairy farming. Overton’s family farmed dairy in northern New York for 150 years. Although his father eventually took a position outside Boston as an Ag lender, Overton returned to his family farm during summers.

As an undergrad, Overton attended Cornell until he graduated in 1991. “I thought, at one point and time, I might want to be a veterinarian like many of our students in animal science do,” reminisced Overton. “Along the way, I became very interested in nutrition.”

After obtaining his doctorate from the University of Illinois, Overton returned to Cornell as a faculty member, where he focused his research on “transition cows.”

A transition cow is in the “transition” stage, or a period four to three weeks prior to birthing when a cow begins producing milk. According to Overtone, during this month, cows are prone to metabolic disorders, including diabetes.

This diabetes associated with pregnancy, also known as “gestational diabetes,” may result from hormones, which create a resistance to insulin.  The molecule, insulin, signals body tissues to absorb glucose.  Diabetes prevents this signal, and when glucose sugar accumulates in the blood stream, the body demonstrates multiple adverse symptoms.

“Part of our work right now, interestingly enough, is focused on insulin resistance in cows before calving,” stated Overton.  “What it looks like is that, cows resemble type two diabetics in some ways, before they calve.”

Lax farm managers sometimes over-feed transition cows, putting cows at high risk for metabolic conditions after childbirth. Overton searches for the optimal energy and mineral balance for cows in the transition period.

“One of our areas of focus has been looking how nutritional strategies for dry cows or cows before calving may influence to what extents they resemble type two diabetics.”

To monitor glucose levels, Overton’s lab uses similar techniques that pregnant women use to test themselves for diabetes.

Overton also examines the behavioral aspects of nutrition and feeding management of transition cows. Overton looks for potential stress elements in the cows’ environment, which negatively impact their feeding behavior.

Many of the current studies of transition cow health examine the effects of “stocking density” on this feeding behavior. Stocking density measures the number of cows in a barn per given area. In some situations, farmers may overcrowd their herd by a small margin, and this overcrowding may harm the cow.

In dense barns, with a limited number of free stalls, cows must stand for excessive periods of time, and due to a limited supply of feeding space, they may frequently binge eat. These actions may lead to metabolic disorders and other health risks.

Overton measures cortisol levels in livestock to assess the presence of stress.

When confronted with the stress, the cow’s adrenal gland produces “cortisol,” a hormone that acts in the regulation of the cow’s metabolism and immune system. By measuring cortisol levels, Overton identifies the direst consequences of stress on the health of the animal.

Using this knowledge, Overton works in the NY dairy extension to help farmers improve facilities and management protocols. In 2007, Overton along with a number of colleagues received recognition for developing the software “Cornell Net Carbohydrate and Protein System (CNCPS).” Commercially available to nutritionists, feed companies and farmers, CNCPS is ration management software that predicts the dietary requirements and feed utilization of livestock.

“We’re really focused on improving animal well-being both through nutritional strategies and other management strategies out on farms, and that of course, that certainly-from our prospective, is a key component of having a sustainable dairy food supply.”

Original Author: Zachary Mason