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Are higher-digestibility forages the basis of a profitable ration?

Kurt Cotanch for Progressive Dairyman Published on 06 August 2018
Cow in the glasses

Advances in forage quality should translate into improved farm income. Forage quality is synonymous with improved fiber digestibility (NDFd).

The primary factors to higher NDFd are: stage of maturity at harvest, plant genetics and the environment (weather).

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Harvesting grasses in the vegetative state, nearly boot stage, and legumes at now bud or pre-bud (at one time quarter-bloom from half-bloom) has increased the yield of highly digestible fiber. Genetic advances in low-lignin corn and now alfalfa allows flexibility in crop management to increase yields of higher-digestibility forage.

The environment then dictates quality in allowing, or not allowing, harvest at optimal stage of maturity. The environment also affects NDFd through temperature and water. Recall that high heat and water tend to decrease NDFd, while cool temperatures and dry conditions tend to increase NDFd. Though lignin is highly related to NDFd, it is certainly not the sole determinant.

Thoughts of low-lignin corn and alfalfa may have some thinking of an easy improvement in forage quality leading to higher milk production and profits. However, great ingredients do not necessarily ensure a great ration or profitable outcome.

Increasingly higher-digestibility forages sound great but, as always, it’s all about the application. How do we best feed highly-digestible forage fiber and for what ends: optimal rumen health, maximized milk and components, minimal feed costs or maximum income?

To attain these goals feeding highly digestible forage requires higher feeding rates of forage. We should know how to do this, as we have been up this part of the learning curve before – recall learning to balance rations with BMR corn silage.

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Here are some thoughts to improve your odds that efforts and costs to produce high-NDFd forage pay off. Focus on the basics of rumen function relative to fiber digestion. Increased NDFd results in:

  • Decreased rumen retention time

  • Faster rate of passage

  • Increased dry matter intake

  • Decreased rumen pH

  • Increased flow of conjugated linoleic acid, which may result in decreased milkfat, perhaps similar to a pasture ration

Whether you prefer “rumen mat,” “chew factor,” uNDFom30 or uNDFom240 (undigested NDF organic matter basis at 30 or 240 hours of rumen fermentation), keep in mind the balance of fast- (rapidly fermenting) to slow-fermenting carbohydrate.

The more fast carbohydrate (high-NDFd fiber, starch, sugar, NFFS) in the ration, the more slow carbohydrate (uNDF30 and uNDF240) is required to maintain proper gut fill and rumination without taking up rumen volume (straw).

That ratio will vary and will depend on individual feeding systems, forages and other feedstuffs. In other words, we do not yet have definitive reference values to provide. Farmers and nutritionists should determine these values unique to each dairy.

Thoughts on improving your returns on efforts to produce highly digestible forages:

1. Lock in pounds of grain, then add forage to match dry matter intake. For example, at only 25 pounds of grain, it may take 35 to 55 pounds of forage dry matter to meet dry matter intake levels. The ration may be upward of 70 percent forage. Based on the yield of components, is this economical for you? Will it result in healthier cows?

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2. What is the energy yield of higher-NDFd fiber? Do cows get more volatile fatty acids out of the more digestible fiber or does the remaining undigested fiber just get out of the rumen faster, allowing for greater dry matter intake of the whole ration?

3. Make sure you have the land base to produce 20 percent more forage. They will likely eat that much more.

4. Reduced-lignin alfalfa may be best fed as dry hay rather than silage. Gains in the rate of intake and digestibility may be greater with dry hay than silage, relative to moisture content when fed. Consider the time required to ingest and hydrate the fiber of the dry versus moist ensiled fiber particle.

Don’t get wooed by the latest technologies. Make sure they fit your farming system.  end mark

ILLUSTRATION: Illustration by Corey Lewis.

Kurt Cotanch
  • Kurt Cotanch

  • Jasper Hill Farm and Creamery
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