Chelsey Carruthers, M.Sc., AAg
Regional Livestock Specialist, Saskatchewan Ministry of Agriculture
Watrous

Every fall with the first frost looming, livestock producers worry about nitrate in their forages. What is nitrate, where does it come from and what can you do about it?

What is nitrate?

During normal growth, plant roots take up nitrogen from the soil in the form of nitrate and the plant converts it to protein. When plant growth is stopped by an event such as hail, frost, drought or chemical damage, this normal process is affected and nitrate accumulates in the plant.

When ruminant animals eat plants containing nitrate, their rumen microbes convert it to nitrite, which is much more toxic. At low levels, nitrite is handled by the rumen microbes and used for protein production. However, at high levels, the microbes can’t keep up. Nitrite is absorbed into the blood stream where it can cause problems by decreasing the oxygen carrying capacity of the blood. Animals can die due to lack of oxygen. Symptoms of nitrate poisoning include trouble breathing, weakness, diarrhea, muscle tremors and death. At lower levels, nitrate poisoning can cause decreased productivity and abortions.

How can you tell?

Nitrate accumulates in the stems and leaves of plants following periods of stress. However, not all plants are equally affected. Nitrate tends to accumulate in annual forages, such as those used for swath grazing and green feed, and some weeds, and is usually higher in immature plants. Legumes such as alfalfa rarely accumulate high levels of nitrate. Crops that have been fertilized with nitrogen will be at higher risk of nitrate accumulation.

After a stress that kills the plant, such as a hard frost, the crop should be harvested as soon as possible. The plants will not recover, and cannot clear the nitrates. Because the plant roots will continue to absorb nitrate from the soil for a few days following plant death, the nitrate level in the plant will continue to rise during this period.

If the stress to the plant has been mild enough for the plant to recover and continue to grow, harvest should be delayed about ten days. This will give the plant a chance to use up the stored nitrate and convert it to protein.

If you suspect your harvested forage is high in nitrate, a feed test can be done to determine the nitrate level. This will give you an idea of what you are dealing with, and what you can do about it.

What can be done?

Not all frozen forages will be high in nitrate. Testing is the only method for determining the nitrate level and developing a plan to deal with high nitrate feed. Most of the time, the risk to livestock can be decreased by diluting high nitrate feed with low nitrate feed. Water can also be high in nitrate, and should be tested as well. A combination of feed and water both high in nitrate can be a more serious problem. Livestock should be maintained in good body condition, and provided with a diet well balanced in energy, protein, vitamins and minerals. Livestock should also be introduced to higher nitrate feeds very slowly, and monitored carefully.

Understanding the process of nitrate accumulation, the risk factors, and the importance of feed testing can help you to plan ahead and deal with high nitrate feeds to protect the health and productivity of your livestock.

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/

Nadia Mori, MSc, PAg, Regional Forage Specialist
Watrous Regional Services Office
Saskatchewan Ministry of Agriculture

Integrated pest management (IPM) is a well established practice in crop protection and can be a valuable approach in forage stand management. IPM means to have a well rounded weed and pest control plan which considers at all options from prevention to control methods available. The following components should be part of an IPM approach:
1.    Monitor Weeds
Monitoring is the process of regularly inspecting pastures to determine if any undesirable plants are present. Scouting also identifies conditions which could favour the development of a weed infestation. For example a recently flooded area on a slightly saline soil may start to convert to foxtail barley.
2.    Pest Identification and Biology
Correct pest identification is necessary in order to select appropriate and effective control measures. Consult with an agrologist or biologist if you are unsure about the identification of a weed or insect found in your pasture. Some basic understanding of the biology of the pest is also critical to effective control and prevention. For example, since annual weeds reproduce by seeds, control measures will be more effective if done before seeds are produced.
3.    Weed Control
Weed control measures must be evaluated in order to select the most appropriate control measures and combine control methods effectively. Herbicide application is one form of control but other alternatives like providing rest during the growing season, mowing, targeted grazing, burning, biological controls and even hand rouging should all be considered. Each control method will have associated costs and make some solutions more economical. For example, cost of weed control procedure, cost of lost production, and cost of damage to non-target plants are some costs to be considered.
4.    Evaluate Weed Control
Control measures must be evaluated to verify the degree of effectiveness. If adequate control has not been achieved, the reasons for the lack of effectiveness should be identified and corrected. Effects on non-target plants and impacts away from the target area must also be identified.
5.    Recordkeeping and Program Management
A complete and accurate set of records is basic to any pest control program. Records will assist in identifying key information such as: which pests have been a problem; where the infestations occurred; how successful different control options proofed to be; what the actual cost of the chosen control option was; during which conditions control options worked or not; which conditions allow certain pests to become a problem (for example, site disturbance, drought conditions, or overgrazing).
For more information, please contact:
    Watrous Regional Services Office (306-946-3220),
    Agriculture Knowledge Centre (1-866-457-2377) or
    Visit our website at www.agriculture.gov.sk.ca.