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Virginia Cooperative Extension - Knowledge for the CommonWealth

Donít Guess, Forage Test

Livestock Update, May 2009

Mark A. McCann, Extension Animal Scientist, VA Tech

The inconsistent rains and growing conditions of Virginia summers usually provide cattlemen with a variety of hay qualities and quantities for the upcoming winter. The goal each winter should be to feed no more than what is necessary and do it as cheaply as possible. Cost savings can be accomplished by feeding the best quality hay at a time when a cowís nutrient needs are at their greatest. To be able to accomplish this, the first and most important step is to forage test your hay cuttings. This will provide the needed information regarding your hay quality. Table 1 contains the crude protein (CP) and total digestible nutrient (TDN) content of three different hay samples.

Table 1 Forage Test Results (DM basis)
  Samples
1 2 3
% Crude Protein (CP) 6.0 8.5 11.0
% Total Digestible Nutrients (TDN) 47.5 52.0 56.5
... Sample 1 is representative of poor quality hay
... Sample 2 is average quality
... Sample 3 is representative of good quality hay

Table 2 contains a comparison of how the three hay samples meet the requirements of a 1200 lb. lactating cow. Another item to note in the table is the difference in estimated hay intake between samples. Cows will generally have a higher intake of higher TDN content hay because it more digestible and has a shorter retention time in the rumen. Therefore the impact of low quality hay on cow nutrition is compounded by the lower consumption and the lower nutrient content. The table also contains the amount of CP and TDN that example hays are deficient in meeting lactating cow’s requirements.

Table 2 Estimated Hay Intake versus 1200 lb Cow Requirements a
  Provided by hay (lbs)   Deficiency (lbs) a
  Daily hay intake Daily DM intake CP TDN CP TDN
Hay 1 25 22.0 1.3 10.5 1.7 5.9
Hay 2 28 24.6 2.2 12.8 .8 3.0
Hay 3 31 27.3 3.0 15.4 - 1.0
a 1200 lb lactating brood cow requirements TDN = 16.4 lbs, CP = 3.0 lbs.
Deficiency = Requirement - provided by hay.

The most evident take home items from table 2 are:

- Feeding low quality hay to a lactating cow will result in a large shortage of CP and TDN which requires a great deal of supplementation or sacrificed cow performance.

- Feeding high quality hay to a lactating cow results in little if any supplement needed.

Most cattlemen can distinguish between their top and bottom hays when the hay is harvested. However, the question then becomes “How good is the better hay and how bad is the poor hay?” The only way to answer that question is to sample the hay and submit the samples to a testing laboratory. VCE Publication Number 404-300 The Basics of Forage Testing discusses in more detail sampling procedures and comparison of results.

Although the implications on cow nutrition are well into the future of next fall and winter, there are a couple of advantages to sampling hay as it is harvested:

     Testing results provide quick feedback as to how successful your efforts in making quality hay were. Many times the weather and other uncontrollable factors (equipment breakdowns, etc) spoil the best intentions. Forage testing indicates how far from the goal the hay quality is and provides some perspective on how much rain or maturity impacted forage quality. Many times the results exceed expectations.

     Second, the early identification of high quality hay can allow decisions to be made regarding storage of the hay if options are available. If limited shelter is available, clearly the best hay needs to be in the dry.

     Third and perhaps most overlooked. Quick testing allows quick identification of cuttings which need to be recorded for future reference. Too many times hay of varying quality is stored together. Next winter it will all look the same when it is covered in snow. As the above table indicates, there are major nutritional impacts on the cow.

     Lastly, correctly matching hay and cow needs is the most efficient and least costly method of feeding cows through the winter. Without a forage analysis, many times additional feed is provided needlessly or inadequate supplementation is provided.

In today’s environment of high input costs and slim margins, having the facts on hay quality can improve the accuracy and cost effectiveness of management decisions.



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