It was July 23, 1999, when two college classmates and I boarded a plane to Madison, Wis. On this date, I began a journey that would change my life substantially. I was a recent graduate in agricultural engineering from the Catholic University of Argentina, embarking on this trip to pursue an internship at USDA’s Agricultural Research Service’s Dairy Forage Research Center. This was my first visit to the United States, and my English was very poor.
Upon arrival, a group of scientists presented their research interests so that we could choose with whom we wanted to work. Among these researchers were Rick Muck, Larry Satter, Glen Broderick, Paul Weimer, and, last but not least, Dave Mertens, whom I chose as my mentor based on his work on carbohydrates. For those who do not know him, Mertens is one of the most prestigious ruminant nutritionists in the U.S. and the world. He is a brilliant scientist, but more importantly, he is a wonderful person.
In our first conversations, Mertens explained to me that a commercial laboratory was seeking to develop a method to better estimate the availability of starch from corn silage. The concern was that some starch from corn silage ends up in the feces, and we needed to find a way to quantify the potential loss. Then, in a very friendly manner, he challenged me, saying, “Think about what you would do to solve this issue.” A few days later, I visited Mertens in his office and brought with me a one-page “research proposal.” More than a proposal, this was a piece of paper with a few bulleted ideas. In a nutshell, the main idea was to pick out whole corn kernels by hand and see what percentage of the total starch in the silage was represented by the whole kernels. I am not sure if Mertens already had this same idea in his mind, but he liked the proposal, and we implemented it.
Having worked for years in the lab, Mertens systematized the procedure, which consisted of drying the corn silage samples and then shaking the dried silage through a set of sieves (as illustrated in the photo ). The most important observation was that whole kernels were retained by a 6.7-millmeter (mm) sieve and that coarse kernel fragments were retained by a 4.75-mm sieve. After determining how much starch was in the silage (StarchCS) and how much starch was in the whole kernels and large kernel fragments (Starch>4.75), we generated a ratio called the fragmentation index (FI). This was calculated as FI = 100 – (Starch>4.75 / StarchCS) x 100.
Twenty-five years have passed since this wonderful experience. The fragmentation index is now known as the corn silage processing score and is widely used by ruminant nutritionists to evaluate the quality of corn silage. As for me, I have been deeply influenced by Mertens, and I have been performing research since those days. One thing I can say to him for sure is: Thank you for your mentorship!
