Rising feed prices have made balancing today’s dairy rations a juggling act. Finding the right balance between milk production and economical feedstuffs can be a challenge. To ease the challenges of balancing rations and feed costs, Kevin Leahy, PhD, PAS, Calibrate® Technologies suggests nutritionists and dairy producers look to the starch content of their diets.
Starch affects rumen pH, microbial growth and overall health of the rumen. Too much starch digested in the rumen can cause sub-acute ruminal acidosis, milk fat depression, reduced intake and lower milk production. Starch content in a ration can be evaluated in three different ways: crude starch, fecal starch or rumen degradable starch.
Crude starch: Calculating the total crude starch in the diet is fairly easy to do by simply adding the starch content from all ration ingredients. “The problem is that this figure doesn’t tell you much outside of how much crude starch you have in a ration,” says Leahy.
Fecal starch: Fecal starch content is calculated by measuring the starch content of a composite of fecal samples from a number of cows, and expressing it on a fecal dry weight basis. “The upside to this figure is if there is a fair amount of starch left in the manure you know you have poorer total tract starch digestion,” Leahy explains. “Typically, we like to see a fecal starch content of 4% or less.” The downside to the fecal starch content calculation is that it gives no indication as to where the starch breaks down in the animal. “You don’t know if the starch is breaking down in the rumen or in the hindgut.”
Rumen degradable starch: A fairly simple calculation, rumen degradable starch provides the most information about the starch value of a ration. “Determining the rumen degradable starch content lets you see how much starch is actually digested in the rumen,” Leahy says. “With this calculation you know what’s happening and where, allowing you avoid issues that come with too much starch digestion in the rumen.”
Feedstuffs can be tested for rumen degradable starch on a routine basis and rations adjusted accordingly. “Knowing the starch content and ruminal starch digestibility of your diet can improve components and overall feed efficiency of the diet,” Leahy says.
For more information on testing for starch, visit www.calibratetechnologies.com.