New test for determining forage quality – high plains journal_ alfalfa u

The latest trend in estimating hay quality is Total Tract Neutral Detergent Fiber Digestibility, or TTNDFD. This new test could replace Relative Feed Value and Relative Feed Quality as the best way to measure forage quality.

Courtney Duxbury, technical nutrition analytic consultant at Rock River Laboratory, Inc., said to think of TTNDFD as how far you can travel on a tank of gas. How far you go depends on how much gas is in the tank (potentially digestible fiber) and what type of miles per gallon you get (NDF digestion rate). TTNDFD is a licensed procedure from the University of Wisconsin.

TTNDFD is measured using standardized and dynamic in vitro rumen digestion measures and is a reflection of real digestion and performance, according to Rock River Laboratory. Measurements are taken at 24, 30 and 48 hours.

“It takes all of these collections points and puts them into one number,” Duxbury said.

According to Rock River Laboratory, TTNDFD forecasts how high-producing cows will respond to a new forage before actually feeding it. Duxbury said forage TTNDFD value change of 2 to 3 points equal 1 pound of milk when forage comprises roughly 50 pounds of the diet. A TTNDFD number above 47 is considered high quality forage.

“Our goal is to come up with some sort of system for using TTNDFD to price forage,” Duxbury said. “I don’t think we are quite there yet.”

Duxbury said the TTNDFD number can be used to measure forage at harvest time, then allocated the forage to different cattle groups based on its quality. It also can be used to assess forage variety improvements.

No matter what you use to determine the quality of your forage, RFD, RFQ or TTNDFD, you need to get a quality sample first. Duxbury said to collect a good sample all you need is a 1- square-foot tool, a small bucket, a bag for the sample and kitchen or garden shears.

The procedure for collecting the sample is fairly simple. Walk into the field, throw the square foot tool on a random spot and work it into the forage. Cut all the stems in the square and then cut these into 1- to 2-inch sections. Repeat this one time every 10 acres. Mix all the cuttings in the bucket and then fill the sample bag about half full.

Hay bales are not uniform. Windrow difference, hay condition and the environment vary from field to field. Duxbury suggested a sampling size of 20 small bales per field or 8 to 10 large bales per field. The best place to sample small square bales is through the center of either end. Core samples can be taken anywhere on large square bales but the core should be inserted at a 45-degree angle to the side or at a 90-degree angle to the end. Duxbury said the round bale should be sampled from the curved side of the bale. The core should be perpendicular to the side of the bale.

Doug Rich can be reached at 785-749-5304 or drich@hpj. com.

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