July 22, 2002

Evaluate Fiber in Alternative Feedstuffs, Dairy Specialist Advises

As dairy producers look for alternatives to high-priced and hard-to-find forages this year, they need to carefully evaluate forages and any substitutes for fiber content, says a North Dakota State University dairy specialist.

"Three measures of fiber should be evaluated in dairy rations: acid detergent fiber (ADF), Neutral Detergent fiber (NDF), and NDF from forage (NDF-Forage)," says J.W. Schroeder of the NDSU Extension Service. The NDF-Forage considers the NDF from hays, haylage, corn silage and 50 percent of the NDF in whole cottonseed. Any NDF from non-forage sources like grains or byproducts other than cottonseed are not considered in calculating NDF-forage.

In addition to the obvious nutrients supplied by forage, they are the primary source of effective physical or cud-chewing fiber that must be of adequate particle length, he says. Cows need a minimum of 15 and preferable 20 percent of the forage particles over 1.5 inches long to stimulate rumination. Cows should chew for 11 to 12 hours per day or about 15 minutes per pound of dry matter intake.

"Many times, significant changes in diet result in noticeable changes in milk production, its composition and cow health," Schroeder notes. "So even though the diet may appear adequate on paper, cow performance is the true test." In order to assess fiber adequacy in the ration, evaluate the following:

Excess fiber – if the level of fiber in the diet is too high, cows will exhibit:

• Low milk production
• Milk production not reaching its peak during early lactation
• Dry matter intake lower than expected
• Higher-than-usual milk fat percent
• Rapid and excessive body weight loss because of low energy levels in the feed. Energy content of feed is generally the inverse of fiber content.

Fiber deficiencies – if the level of fiber in the diet is too low, cows will exhibit:

• Acidosis, off feed problems, fluctuating dry matter intake and sore feet
• Low milk fat percent, fat-protein inversions
• Cows not chewing their cuds
• Loose, watery, grayish feces

"There is no one best diet for all dairy cows," Schroeder says. "Work with your nutritionist and base your ration changes on the feedstuffs you have available."

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Source: J.W. Schroeder, (701) 231-7663, jschroed@ndsuext.nodak.edu
Editor: Tom Jirik, (701) 231-9629, tjirik@ndsuext.nodak.edu

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Graphic 1 --

Fiber Ration Guidelines for Lactating Dairy Cows
------------------------------------------------
                          Lactation Stage
                    ----------------------------
Fiber Measure         Early   Mid   Late   Dry
------------------------------------------------
ADF, minimum           18*     20    21     28
NDF, minimum           28      28    32     35
NDF-forage, minimum    20      21    21     25
NDF-forage, maximum    24      26    28    ---
------------------------------------------------
------------------------------------------------
* Increase to 20 percent minimum when fat 
  is added to rations.

Graphic 2 --

Particle Size Guidelines for Forages and 
Total Mixed Rations (TMR)
-----------------------------------------
                Seperator Box Level*
            -----------------------------
Feed           Top     Middle   Bottom
-----------------------------------------
            ---- percent by weight ----
Chopped hay  15 - 25  40 - 60    < 30
Haylage      15 - 25  30 - 50    < 40
Corn silage    < 5    50 - 65    < 40
TMR            > 7    30 - 50    < 50
-----------------------------------------
-----------------------------------------
* Adopted from Penn State Forage 
  Seperator Box recommendations.