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Harvesting forage for quality or quantity

Mike Jerred Published on 20 July 2010
tractor on silage pile

The harvest season is upon us, and one question that often comes up is the proper balance between forage quality and forage quantity. In this article I would like to explore a few of the issues that can go into making the right decision for your operation.

Let’s start by looking at some of the major forage crops. Alfalfa and grass hay or silage decisions are straightforward. Forage quality is paramount for these crops. From a nutrition point of view, leaving the crop in the field to increase yield will increase the NDF content of the crop and the digestibility of the NDF will start to decline.

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Most of the gain we would receive from the increased tonnage will be given away in reduced digestibility and lost efficiency in the diet. Over a full growing season, tonnage gains are minor using a less aggressive harvest interval between cuttings, if you end up harvesting the same number of growing days. For example, a four-cutting strategy using 35-day intervals will cover 140 growing days. A five-cutting strategy using 28-day intervals covers the same 140 days. Grass is particularly sensitive to maturity impacts on quality. You want to harvest in the pre-boot to boot stage for high-quality forage.

Small-grain silages are one crop where we have some options. Harvesting once means we will not be able to pick up tonnage later on through additional cuttings, so waiting to harvest will have a significant impact on forage quantity. On the quality side we end up with a trade-off. Just like alfalfa and grass, increasing maturity of small grains will increase the NDF content and decrease the NDF digestibility of the stalk. Unlike alfalfa and grass, we are also gaining starch content of the overall plant as the grain head forms so the impact on total energy from the crop is minor. This is where you need to ask yourself and your nutritionist a few questions. “Do I need additional inventory of forage? Which diets will utilize this small-grain silage? Is starch or digestible fiber more valuable to my diets?” One last caution on small-grain forages. It is critical to watch the moisture content of the crop to ensure it does not become too dry for proper storage and fermentation.

Corn silage is a crop where the quantity-versus-quality decision is often overridden by another factor. The primary driver of corn silage harvest is proper whole- plant moisture for storage and fermentation. Growing season and plant variety can impact the overall plant and grain maturity, impacting the exact nutrient composition of the silage, but those differences in starch, NDF and NDF digestibility must be accounted for through forage testing and diet formulation.

The discussion so far has focused mainly on the timing of harvest and how that can impact the nutrient content of the crop as it comes off the field. One other aspect of this quality-versus-quantity discussion that is often overlooked is the storage of the crop. Storage conditions cannot take a poor-quality crop and turn it into good-quality feed, but it certainly can take a good-quality crop and turn it into a poor-quality feed. Storage conditions can also dramatically impact the final quantity of the crop that we have available to feed to the animals.

Let’s look at the quality aspect first. There are many factors which can impact the ultimate forage quality reaching the animal, and the details are beyond the scope of this article. Silage quality ultimately starts in the field. It is critical to deliver forage to storage at the proper moisture, chop length and with low ash content. Once there, the key factors include packing to remove air, providing an effective seal, applying a high-quality inoculant and using good feedout technique.

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Following these good management practices to maximize forage quality will also help reduce storage losses and help us maximize our inventory. It is often easy to overlook the impact of dry matter loss in storage because we do not see it happening directly. In fact, in many cases the shrink loss that occurs in storage can easily outweigh any gains in the field through delayed harvest. Let’s look at an example of an operation feeding 70 pounds of silage per day. Reducing dry matter loss by 5 percent during harvesting, storage and feedout will result in a savings of 100 tons of silage for every 100 cows in the operation. At an average value of $50 per ton, that is a annual savings of $5,000 per 100 cows.

The quality-versus-quantity decision begins as a harvesting decision and does not end until the forage has been fed to an animal. The actions taken all along this supply chain will impact the ultimate nutrient value of the forage and the total inventory available to feed. In most cases the harvesting decision should focus on maximizing forage quality and ensuring the crop will pack and ferment properly to minimize dry matter loss and maximize nutrient retention and availability. PD

PHOTO : It is critical to deliver forage to storage at the proper moisture, chop length and with low ash content. Once there, the key factors include packing to remove air, providing an effective seal, applying a high-quality inoculant and using good feedout technique. Photo by Walt Cooley.

Mike Jerred
  • Mike Jerred

  • Global Dairy Leader
  • Cargill Animal Nutrition
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