Grazing Unharvested Swaths

October 2008

Saskatchewan Agriculture has a publication entitled "Swath Grazing" but it is important to understand that the information it contains does not pertain to grazing mature crops that have been swathed. Normally, crops used for swath grazing are cut in the early to mid-dough stages of development when the crops are green, leafy and contain good levels of protein and energy. When a crop has matured and swathed for harvest, it is composed essentially of grain and straw, and needs to be treated in an entirely different manner.

Producers should exercise caution when letting cattle graze mature swaths.

Grain accounts for 40 to 60 per cent of the weight of the swath in a mature crop. A 1,200 lb. cow in mid-pregnancy eats about 26 lb. of dry matter each day. A cow feeding on a swathed, mature crop will consume about 15 lb. of straw and 15 lb. of grain daily. Under these conditions, there is a high risk that the cow will develop grain overload, free gas bloat or acidosis. The ingestion of high amounts of grain also fosters the development of lactic acid and acid-tolerant bacteria in the stomach. This can damage the rumen wall, allowing bacteria to enter the blood stream and form liver abscesses. Some animals may develop laminitis or founder. Scours or diarrhea is common under these conditions, and is a good indicator of digestive upset. Cattle with more severe cases of grain overload experience abdominal pain and often become recumbent.

Due to the higher risk of acidosis, the best option for using unharvested wheat, durum, and rye crops is to thresh the swaths, then coarsely grind or roll the grain and feed it according to acceptable recommendations. Processing the grain increases its digestibility by 20 per cent or more. Limit wheat and rye to 40 per cent or less (durum 30 per cent or less) of the ration in backgrounding and finishing diets. Do not feed more than six lb. of wheat (4.5 lb. of durum) to a mature cow daily. Rye fed to dry pregnant beef cows can constitute all of the supplemental grain or 40 per cent of the total ration, whichever is less. Ergot levels should not exceed 0.1 per cent. Slowly accustom cattle to these grains by starting at low levels (10 to 15 per cent of the diet) and gradually increase the amount fed. Do not abruptly start or stop feeding high levels of grain.

Oats, because of its higher fibre content, can be fed at higher levels. It is usually not economical to process oats as the digestibility is only increased by three to five per cent. If feeding more than eight to nine lb. of barley or oats per mature cow per day, divide the grain into two equal portions and feed one portion in the morning, and the other later in the day.

Another option for salvaging the grain is to bale the unthreshed swaths. It is not advisable to give cattle free access to these bales in a bale feeder, as the cattle may selectively eat the grain which can lead to grain overload. Instead, use a bale processor, tub grinder or bale shredder to blend the swath-bales in a 50:50 mix with good quality hay bales. This reduces the total amount of grain intake and ensures that there is a source of protein in the ration.

If there is no other option but to allow cattle to graze the swaths, it is recommended to force the cattle to intensively graze small sections of the swath by fencing off the rest of the field with an electric fence. "Freeze-proof" posts can be made by welding a four or five foot section of 1/2-in. rebar onto old "one-way" blades or tire rims, and attaching insulators directly to the rebar. The "posts" are easily moved and do not freeze into the ground, allowing the cattle to be moved through the field until the swaths have been thoroughly and intensively grazed. If the animals are allowed free access to the swaths they will sort out all the grain and not clean up all the stalks, which can result in problems in the spring.

When allowing cattle to graze mature swaths, it is important to understand that grain and straw alone do not make a sound ration. A source of additional protein and vitamin A is also necessary. Providing bales of good quality hay may be the least expensive method of supplying protein. The hay should supply about one-half of the total feed intake each day. Another option is to provide cattle with lick-tanks or protein-molasses tubs.

Another point to consider is excessive rates of gain. During mid-pregnancy, a 1,200 lb. cow consuming 14 lb. of grain, 14 lb. of straw and one lb. of protein supplement will gain about one lb. of body weight per day. This may not cause problems in the short term, but long-term feeding may place excessive weight on the cattle, which could cause calving difficulties due to the deposition of fat in the birth canal.

For more information, contact:
Agriculture Knowledge Centre
Toll free: 1-866-457-2377
E-mail: aginfo@gov.sk.ca