Forage Quality Goals for 2009

Composite data for 2008 haylages (Figure 1) shows that the average of legume and mixed haylages are very close to the target RFV of 150, writes Jim Paulson, University of Minnesota, Dairy Extension.
calendar icon 28 June 2009
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However, we see a wide range in all measurements of quality and many very high in Crude Protein (CP), Neutral Detergent Fiber Digestibility (NDFD), RFV and Relative Feed Quality (RFQ). This would indicate many producers often desire a haylage that is higher than 150 RFV. This may be due to wanting higher crude protein but may also reflect the ability to get greater intakes and greater milk production from such forage. What should be our goals for 2009?

Figure 1. 2008 Quality data by haylage type.
  Legume Mixed
  Range Average Range Average
CP, % 15.6 - 25.5 20.5 14.3 - 25.6 20.1
NDF, % 31 - 49 40.1 30.4 - 52.3 41.3
NDFD, % 44 - 63.6 53.8 35.2 - 57.1 46.1
Lignin, % 5.6 - 10.3 8.0 5.4 - 10.8 8.1
RFV 103 - 200 152 95 - 197 146
RFQ 107 - 239 173 100 - 235 167

What numbers are important as we look at our forage analysis? A typical forage test report may have over 30 numbers to consider. The categories on the chart are items that I consider important for a quick assessment when feeding dairy animals. Figure 2 provides some goals and guidelines depending on the group of animals we are feeding.

Figure 2. Forage quality goals for 2009.
  Hay or Haylage Hay or Haylage
Dairy animal Lactating cows Heifers <6 months Heifers, breeding age Dry cow, pg heifers
CP, % >22% 20 - 22 16 - 18 13 - 15
NDF, % 38 - 42 40 - 42 40 - 45 45 - 55
NDFD, % 55 - 65 50 - 55 45 - 55 40 -50
Lignin, % <8.5 8.0 8 - 10 8 - 10
RFQ >165 >150 >136 >125

Relative Forage Quality is an index for ranking forages based on dry matter intake (DMI) and total digestible nutrients (TDN). RFQ = (DMI, % of BW) X (TDN, % of DM). While the formulas are different for both DMI and TDN between grasses and legumes, NDFD is part of both equations. Relative Feed Value is based on Acid Detergent Fiber (ADF) and Neutral Detergent Fiber (NDF) but due to variability in measuring ADF and not using digestibility in the equation, accuracy of forage value has been more difficult to ascertain. Also, under the RFV system, grasses were typically undervalued due to the fact that lignin was not measured and NDFD not determined.

With the introduction of RFQ, we have the ability to better predict digestibility of forages. Should we change our target number? I think it depends on our target animal to be fed. If we are feeding lactating dairy cows, I feel we should now target RFQ at >165. This should provide forage with an NDFD of >50% and CP levels of >22%. This quality of forage would result in greater intakes and be able to support higher milk production due to greater digestibility of NDF.

Can we get forage quality too high? That is a question I hear frequently. The answer to the question is: a) probably not; b) it depends; c) sure; or d) all of the above. It depends on what we are feeding it to, how much we are feeding, and what else we are feeding along with it. For high producing dairy cows that are fed a balanced ration with adequate amounts of NDF from forage, forage quality can be very high and needs to be in order to support high production. On most dairy farms, without a concentrated effort to put up high quality forage, the forage can often fall below optimum.

Matching the right forage to other classes of dairy animals may mean utilizing forage that wasn’t harvested at top quality due to weather or other factors. It may also mean designating older stands for dry cows and bred heifers or specifically planting a mix that will be higher in fiber and lower in protein, such as a grass mix that is left to mature.

Make a determined effort this year to allocate the optimum forage to the right group of dairy animals on your farm and save money in these tight economic times.

Good luck with your forage harvesting in 2009!

June 2009

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