12 Aug 2022

Neutral Detergent Fiber determinations in dairy cattle. Why are they important?

Analyses that contribute in assessing forage quality have become widely adopted by dairy producers. These evaluation methods have become highly influential when it comes to ingredient purchasing and diet formulation for dairy cattle.

Neutral Detergent Fiber determinations in dairy cattle. Why are they important?

Neutral Detergent Fiber determinations in cattle have become a necessity for producers. This is especially true for the dairy industry.

Introduction

The ability of transforming fiber into energy and protein for human nutrition is a key role of ruminants within our food system. Ruminants’ unique capacity to digest fiber, a growing human population which increases competition over croplands, and higher feed concentrate prices are all reasons that highlight the importance of forage inclusion in ruminant nutrition. Therefore, being able to produce and include high-quality forages within dairy cow diets, is a key determinant in dairy farm profitability. Analyses that contribute in assessing forage quality have become widely adopted by dairy producers. These evaluation methods have become highly influential when it comes to ingredient purchasing and diet formulation for dairy cattle.

Neutral detergent fiber

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Neutral detergent fiber (NDF) is a measure of the proportion of cell wall in plant tissue, expressed as a proportion of total dry matter. Adequate NDF in dairy cow diets enables proper rumen function, but the challenge of feeding increasing neutral detergent fiber concentrations to high-producing dairy cows is that it may lead to excessive gut fill and limit feed intake.

Neutral detergent fiber

The level of neutral detergent fibre in the animal ration influences the animal’s intake of dry matter and the time of rumination. NDF is the most common measure of fibre used for animal feed analysis. It measures most of the structural components in plant cells (i.e. lignin, hemicellulose, cellulose).

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“When a forage has a very high NDF, it is negatively correlated with lower consumption. That is, the animal fills up faster. Forage with low Neutral Detergent Fiber means the cow has more food in the rumen and can produce more milk,” asserts Jorge Mario Noreña, agronomist and professor at the National University of Colombia in Medellín.”

The Department of Employment, Economic Development and Innovation in Australia, limits the NDF intake for ruminants:
Optimum intake is achieved

when NDF content

= 28% to 34 % of total diet dry matter
Maximum NDF intake

from forage

Example: 1% x 600 kg cow = 6 kg of NDF from forage = 1% of the cow’s body weight
Maximum NDF intake

in the total ration

Example: 1.2% x 600 kg cow = 7.2 kg of NDF from the total diet = 1.2% of body weight (1.3% for a high-producing cow)
In order to achieve a balance between feeding enough NDF to support rumen function without exceeding the amount fed and limit feed intake, dairies have become highly dependant on in vitro NDF digestibility (ivNDFD) measures.
The ivNDFD is the proportion of NDF that is digested after some amount of time (24, 30, 48, or 240 hours) in a flask with buffered rumen fluid (containing live ruminal bacteria) from a donor cow. Undigested NDF (uNDF) is a related measure and is simply the portion of NDF that was not digested after some time (usually 240 hours) of in vitro fermentation.

Feed analysis laboratories offer these NDF digestibility assays, but they are time-consuming for the lab and therefore costly. To reduce the cost of acquiring these estimates, many laboratories offer near infrared reflectance spectroscopy (NIRS) predictions of ivNDFD as an alternative to “wet chemistry.”

Neutral detergent fiber

Near infrared assessment of NDFD

NIRS instruments bounce specific wavelengths of light off feed samples and measure the light absorbed or reflected back. The patterns of absorption and reflectance are indicative of the chemical composition of the feed material tested. To make use of these patterns, reference feeds are analyzed both with wet chemistry methods and by NIRS, and prediction equations are built from those relationships. It is important to note that NIRS analysis cannot be more accurate than wet chemistry analysis from that particular lab.

 

Best practices for NDFD analysis

To get the most value from investments in NDFD analysis, it is important to consider the following:

NDF digestibility is mainly influenced by maturity:

  • Grass silage and hay have a very wide range of NDF digestibility because grass species are so diverse and are utilised at extreme ranges in maturity (e.g. grazing vegetative grass versus feeding straw).

  • Corn silage can have a wide range of NDF digestibility, but it is uncommon to see the extremes because corn silage is harvested and stored within a relatively narrow range of maturity. Extremes in corn silage NDF digestibility can occur when corn silage is harvested at an over mature stage (NDF digestibility = low), or when a brown midrib variety is used (NDF digestibility = high).

  • Conclusions

    Source:Abstract taken and modified fromMaking use of NDF digestibility analyses for dairy cattle diets.”

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