Don't Guess, Forage Test

Targeting best forage at an animal when it needs it the most is part of cost effective feeding, says Dr. Mark A. McCann, Extension Animal Scientist, Virginia Tech.
calendar icon 5 November 2013
clock icon 4 minute read

For this reason, testing hay and silage cuttings can provide useful data about the most valuable parts of the crop.

"Virginia's plentiful summer rains provided us with far more forage than we have been accustomed to. However, the rains also provided a challenge in harvesting quality forage," says Dr McCann. 

As a result, cattlemen are faced with a plentiful quantity of hay with a limited amount of high quality forage for the upcoming winter, he writes. 

More hay than normal was rained on during the drying period. This always gives rise to the question of how much the rain decreased the nutritional value. There is no standard change in quality that you can bank on other than it will be reduced. How much depends on quantity of rain, 1st or 2nd cutting, how soon after mowing the rain occurred, etc.

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 cow's 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. This year a forage test is more important due the impact of weather on forage maturity at harvest and rain damage prior to baling.

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)

- 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)

(a) 1200 lb lactating brood cow requirements TDN = 16.4 lbs, CP = 3.0 lbs.
Deficiency = Nutrient requirement - nutrient 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 the poor hay is?"

This year we have the additional question of 'How much did the rain damage my hay". The only way to answer these questions 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.

  • 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.
  • Lastly, correctly matching hay and cow needs is the most efficient and least costly method of feeding cows through the winter. Without 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 and supplementation decisions.


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