December 8, 2020 - If you are feeding livestock, forage analysis is critical
Available nutrients may not be what you think they are
2020 was a productive year for agricultural producers in Clearwater County. Plenty of spring moisture made for some tough seeding but crops and forages flourished as a result. Hay stands were the best many had seen in years, resulting in lower prices, but no shortage of feed for livestock.
As rain persisted sporadically through the summer, moisture on cut forages caused some leaching of nutrients like soluble carbohydrates, proteins and some minerals. In alfalfa, the browning resulted in leaf loss, the plant portions that contain the greatest amount of nutrients.
Intermittent wet weather also created a greater risk of heating and mold growth in bales, which can promote mycotoxins. If forages were damaged by hail and harvested too soon thereafter, nitrate poisoning could also be an issue.
Feed analysis and ration balancing are always a good idea. Nutrient composition can vary widely, even in forages harvested off the same field in the same year, depending on environmental conditions and cutting time.
Low quality forages have less available nutrients so supplementation will be required in many situations. Generally speaking, if the forage is green in colour then it is likely higher than seven percent crude protein. If it is brown in colour then the crude protein is probably less than seven percent.
As a rule, cattle require a minimum of seven percent protein from forage without supplementation. Pregnant cows generally require a minimum of nine percent while lactating cows require 11 percent.
The rumen is full of micro-organisms that need to be fed to unlock nutrients. Those micro-organisms require the nitrogen found in protein to digest forages.
If there is a lack of nitrogen in the rumen then microbial efficiency will be reduced and digestion will slow down with less energy released. The result is that cows lose condition and become prone to other ailments.
Relatively inexpensive, feed analysis is the only way to accurately determine forage quality and nutrient composition. Forage fiber content is the primary detractor to high intake and nutrient availability and the single best method to determine feed quality.
A short description of the factors most commonly analyzed are indicated below.
Moisture and Dry Matter: Percent moisture indicates the amount of water in the feed. Dry matter is the balance of the percentage out of 100. For example, if the forage sample is 12 percent moisture, then the dry matter will be 88 percent. Most labs will indicate nutrients on both an "as fed” (water in) basis and "dry matter” (water out) basis.
Protein: Crude protein is a good indication of quality. It is determined by multiplying the analyzed nitrogen content and multiplying it by 6.25 percent. Available protein is crude protein minus heat damaged protein.
Fiber: The detergent feed analysis system is used to determine fiber or total cell wall content of a forage or feed. The portion insoluble in neutral detergent is termed neutral detergent fiber (NDF) and contains the primary components of the plant cell wall. As a plant matures the NDF content will increase. A good measure of feed quality, an NDF below 40 percent in legumes and below 50 percent in grasses, would be considered good.
Energy: Another measure of fiber is acid detergent fiber (ADF) which contains the poorly digestible components and is used to predict energy content. The higher the number the lower the quality with a goal of less than 35 percent ADF in grass or legumes.
Relative Feed Value (RFV): is indicated by a single number calculated from ADF and NDF excluding protein. Having no specific nutritional meaning it simply allows for easy comparison between forages.
Minerals: Calcium, phosphorous, magnesium and potassium are the elements commonly included. If more precise mineral results are required, then additional testing using wet chemistry may be requested.
Total Digestible Nutrients (TDN): The concept of total digestible nutrients comes from the old system of measuring available energy of feeds and energy requirements of animals involving a complex formula of measured nutrients. TDN values are usually quoted as percentages for feeds and as amounts per day for requirements.
Clearwater County Agriculture and Community Services provides forage sampling tools to local producers free of charge along with lab sample request forms. Ag staff will also suggest appropriate sampling methods and assist with interpretation of test results.
In addition, a free CowBytes ration balancing service is also available to help local livestock producers determine the appropriate nutritional requirements for their animals. Feel free to give us a call at 403-845-4444.
Foothills Forage and Grazing Association
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