Using In Vitro Total-Tract NDF Digestibility In Forage Evaluation

Apr 13, 2016

Fiber is an essential component of diets for dairy cattle. In high producing dairy cows, about a quarter of the energy for milk production comes from digested fiber. Neutral detergent fiber (NDF) is a laboratory assay done on forages to measure the total content of fiber in a feed. The NDF is a ‘bulky’, slow to digest feed component, which can restrict feed intake and milk production. Forages are analyzed for NDF content and diets for lactating dairy cows are typically formulated to contain 28% to 35% NDF on a dry matter (DM) basis depending primarily on level of milk production and the feed ingredients being used in the diet.

The digestibility of NDF also profoundly affects feed intake and milk production. Fiber digestibility can have a much greater impact on milk production than the digestibility of any other feed component. The digestibility of the fiber in 38%-NDF alfalfa can vary from 30% to over 60% of the NDF. In a dairy ration containing 15 lb. DM of this alfalfa, a doubling of fiber digestibility would increase the intake of digestible energy enough to support up to 8 to 10 lb. more milk per cow per day.

A new in vitro lab assay has been developed by UW-Madison Dairy Scientists that predicts total-tract NDF digestion in ruminants. The in vitro total-tract NDF digestibility (TTNDFD) test predicts NDF digestion for alfalfa, corn silage, grass forages and byproduct feeds. UW-Madison researchers have validated the accuracy of the in vitro TTNDFD test against directly measured NDF digestibility in lactating dairy cattle. The University of Wisconsin recently was awarded a patent for the in vitro digestibility procedure that is used in calculation of TTNDFD. In the UW-Extension Team Forage Focus on Forage paper Using In Vitro Total-Tract NDF Digestibility in Forage Evaluation, UW-Madison Dairy Scientist David Combs reviews the TTNDFD test and discuss its use in forage evaluation.

Source: uwex.edu

Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.