Late Season Hay Production: Overcoming Protein Deficiency

September 23, 2015 03:05 PM

As the summer progresses and hay matures, haying season should be coming to a close, however some producers are getting one last cutting. ​
By: Taylor Grussing, SDSU Extension Cow/Calf Field Specialist

Although it is late in the season, producers may want and/or need to put up this hay in order to have adequate feed stored for the winter. However, there will be limitations on how this harvested forage can be utilized.

In late harvested forages, the nutrient composition is compromised compared to earlier cuttings due to the often extreme heat seen in July and August.  Inducing hay to grow slower and use its available nutrients to simply survive, thus depleting reserves that would have been available at harvest. Protein becomes the first limiting nutrient and digestibility of total dry matter decreases in these forages. In general the protein content of the forage may be deficient, but just exactly how much lower is it?

Forage Testing 

A good rule of thumb with all harvested forage, especially late cut, is to have a complete nutrient analysis conducted in order to know how the forage can be utilized in winter feeding programs. For steps on how to obtain a forage sample refer to the the embedded video above. A listing of Feed Testing Laboratories is also available on iGrow.

Once the nutrient analysis from late harvested forage is received, it will likely show that the forage is deficient in protein and will require supplementation in order to meet the cow’s protein requirements. This lower protein forage may be used for dry cows with lower nutrient requirements than lactating cows; however, the option to save specific hay for specific animals is not always practical. Therefore, pairing low protein hay with a protein supplement is one way to utilize these forages at any time.

The amount of protein to be supplemented will be dictated first by the quality of the forage. For example late harvested meadow and prairie hay will have less TDN and CP than late cut alfalfa hay. Secondly, the cow’s stage of production will provide a target for the amount of protein that may need to be supplemented with the forage (mid-gestation = 7-7.5% CP, late gestation = 7.5-8% CP, lactation = 10.5-12.5% CP). Regardless of production stage, cows first require a minimum of 7% CP for adequate rumen function. By first meeting CP requirements of the rumen, the microflora can function to efficiently digest fiber, which then stimulates forage intake.

Choosing a Protein Supplement

There are several factors to consider when choosing a protein supplement to pair with late harvested forage to meet cow requirements but not break the bank. Criteria such as cost per ton of protein, quantity to be consumed, and price of delivery and labor need to be considered.

Types of protein supplements that may pair well with low quality forage include:

  • Alfalfa
  • Distillers grains or other ethanol coproducts
  • Range cubes
  • Protein tubs
  • Liquid protein feeds


Depending on the protein content of the forage, the amount of protein cows need to meet their requirements will vary based on protein in the supplement. Severely protein deficient hay will require cows to consume a greater quantity of protein supplement; therefore palatability becomes a factor in determining which supplement cows can physically consume enough of to meet requirements. They will consume on average 2% of their body weight in DM per day; therefore, the TDN and CP content of the hay may limit the amount of supplement they can consume. Also, depending on how the supplement is fed, cows may eat the supplement first and consume less forage; thus supplementation may be one way to maintaining the same cattle on less forage. Distillers grains and high quality alfalfa contain 29.5 and 16 - 20% CP, respectively. While protein tubs or liquid feeds have a wide range of crude protein (15% to 40%), consumption is limited to 1.5 – 2 lbs. per day. Therefore, the protein content of the supplement will help determine how much cows need to consume each day and determine which supplement can be delivered most effectively to meet protein requirements.


Lastly, it is important to compare supplement on a price per ton of protein basis. For more information on how to calculate cost per ton of protein refer to Consider Nutritional Value When Buying Hay.

Additional factors that need to be calculated in the price include:

  • Number of cattle
  • Quantity and shelf life of supplement
  • Supplementation Frequency
  • Delivery charges (labor, equipment, fuel, convenience)
  • Type of delivery (bunk vs. range: calculate waste)

After considering these factors, the cheapest supplement may not be selected, but one that best meets the cow’s nutrient requirements and your operation most efficiently, while not decreasing production in the long term.

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