Clearwater County Highlights October/November | Page 26

26 | NOV. 2016

Late Grazing of Standing Crops can Present Challenges
Some Suggestions to Reduce the
Potential Risks Involved

Nitrate
poisoning occurs
when plants
become stressed
and unable
to metabolize
nutrients taken
up by the roots,
particularly
nitrogen.

www.clearwatercounty.ca

Well into October, many producers are
attempting to finish haying while harvest is
delayed due to high moisture levels and fields
too wet to drive on.
This late in the season, cattlemen may be
considering grazing standing cereal crops
or unbaled hay in an effort to salvage some
value. Given heavy frosts, nitrate poisoning
may be a concern.
Nitrate poisoning occurs when plants become stressed and are unable to metabolize
nutrients taken up by the roots, particularly
nitrogen. High levels of nitrites impair the
ability of blood hemoglobin to carry oxygen.
Symptoms of nitrate toxicity include rapid
breathing, muscle tremors, staggering and
death.
Late-baled forages and greenfeed also run
the risk of stress as a result of frost prior
to cutting; a $35 for a nitrate test may be a
worthwhile investment.
Annual crops can accumulate nitrates more
readily than perennial crops. Late-seeded
crops are more of a concern since nitrate concentration is usually highest in young plants,
decreasing as plants mature.
Grazing crops that contain moderate to
moderately-high nitrate concentrations are
not without risk; an evaluation should be
completed.
Initial nitrate testing of the crops to be
grazed will indicate where concentrations are
highest. Pay attention to locations heavily
fertilized or manured.
Moderate risk levels of nitrate nitrogen
(NO3-N), based on parts per million (ppm),
would be in the area of 1100-2100 ppm, while
high risk levels would be 2100-3400 ppm.
Grazing crops at levels that exceed 3400 ppm
is not recommended.
Moving cattle from depleted pasture to
richer ripened grain or regrowth alfalfa could
pose potential problems like bloat, impaction

and acidosis. Cattle filled up on hay are less
likely to overfeed.
Fencing off smaller areas will force cattle
to do a better job of cleaning up. Late spring
grazing may be necessary to utilize the aftermath assuming nitrate levels are not too high.
Lower risk cattle such as open cows are
recommended, followed by growing calves
or replacement heifers (prior to breeding);
pregnant cows are at greatest risk.
Gradual adaption is a key management
strategy that will reduce risk. Grazing the lower nitrate fields first will help them to adapt.
Given gradual exposure cattle develop greater
numbers of bacteria in the rumen capable
of degrading nitrite to ammonia for bacterial protein synthesis. If the only option is to
graze fields with higher nitrate levels animals
should only be allowed to graze lightly at first.
Nitrate levels can also vary throughout
plants. Higher levels tend to accumulate in
the lower stem so overgrazing will cause an
increased intake of nitrates and increase risk
of nitrate toxicity.
Supplementation may be necessary this
winter, given the lower quality of this year’s
forage.
Agricultural Services and Landcare provides
free ration balancing to local farmers using
the Cow-Bytes system. Drop in or give us a
call at 403-845-4444 to make the best of your
feed resources this winter.