by:Chelsey Carruthers, M.Sc., AAg
Regional Livestock Specialist, Saskatchewan Ministry of Agriculture
It’s that time of year again when cows are coming in from pasture, and beef producers must begin the task of planning their winter feeding strategy. A great first step is to have forages tested by an accredited laboratory. A standard forage quality test provides the information necessary to decide whether the feed you have available will meet the requirements of the cow herd during the winter months. You can then decide when each feed can be used to best meet the cows’ requirements, and if supplementation of energy, protein, or minerals will be necessary.
Forage tests provide information on the moisture, energy, fiber, protein and mineral content of feeds. These may be reported on an “as is” or “as received” basis, or on a “dry matter” basis. Dry matter values are reported as if the feed contained no moisture, and this is important when comparing values between feeds that have different moisture contents. The values discussed in this article are reported on a dry matter basis.
Energy is reported in feed tests in a number of ways: total digestible nutrients (TDN), digestible energy, and relative feed value. TDN is the most common, and is expressed as a percentage. On average, mature beef cows require 55 per cent TDN in mid pregnancy, 60 per cent in late pregnancy, and 65 per cent after calving in order to maintain their body condition. Energy requirements will be higher during very cold weather, for cows that are underweight, and for young cows that are still growing. Average quality hay often contains 50 to 60 per cent TDN, while poor quality hay can be less than 45 per cent. Straw contains 35 to 40 per cent TDN. If cows are fed a diet containing only forage, that forage must meet their energy requirement. If not, feeds higher in energy (such as grain or pellets) can be added to the diet to provide the energy required.
The fiber content of feed is related to the amount of energy that is available to the cows. Fiber is expressed on forage test results as neutral detergent fiber (NDF). A higher number indicates more fiber in the feed. When NDF is higher than 60 per cent the feed will be very fibrous and bulky. Cows may have trouble physically consuming enough feed to meet their energy requirement.
Protein is measured as crude protein (CP). Cows require approximately 7 per cent CP in mid-pregnancy, 9 per cent in late pregnancy, and 11 per cent after calving. Forages will vary greatly in protein content, but in general, legume hay such as alfalfa or clover will be higher protein than grass hay, and cereal green feeds will be lower in protein than hay. Grains are also relatively low in protein. Protein is often supplemented in the form of pellets or lick tanks, which can be used to increase the protein content of the total diet. It is important to keep in mind that protein supplements will not compensate for forage that does not contain sufficient energy.
Most feed tests also report the mineral content of the forage. Calcium and phosphorus are the most important minerals to consider. The complete diet should contain at least 0.25 per cent calcium and 0.17 per cent phosphorus. More importantly, the diet should contain at least 1.5
times more calcium than phosphorus. Minerals often need to be supplemented using one of the many products available. Speaking with a nutritionist can solve the mystery of which mineral supplement to use with your forages.
As with many things, the first step to planning a winter feeding program is to know what you have to work with. Forage testing is a valuable tool for determining the most effective way to use your feed resources.
For more information on this or other topics please call me at (306) 946-3237, the Agriculture Knowledge Centre at 1-866-457-2377 or visit our website: http://www.agriculture.gov.sk.ca/