Page 28 - MWC 04-22-2021s

The Midwest Cattleman · April 22, 2021 · P28
Grass Tetany/ Hypomagnesemia–

Start Preventive Measures Now

By Dr. Michelle Arnold, Ruminant Extension Veterinarian, University of Kentucky

What is “Grass Tetany” types, soil fertility, diverse urine. Salt, as with any sub- clinical cases occur but there
and when are cattle most forage species and differing stance, can be dangerous and are many unobserved or sub-
likely to have it? Grass cattle requirements based even fatal at high levels. For- clinical cases that may be-
tetany, also known as spring on age and stage of lactation tunately, a second, “passive come problems after a stress-
tetany, grass staggers, wheat result in different mineral transport” system for Mg ex- ful event such as a weather
pasture poisoning, winter needs for grazing livestock ists which is not influenced change.
tetany or lactation tetany, is on every farm. A blanket by potassium. This transport How Can Grass Tetany
a condition resulting from a recommendation to just feed system only works when sol- Be Prevented? Prevention
low level of magnesium (Mg) salt ignores these factors uble Mg in the rumen fluid is based on providing mag-
in the blood. Maintenance of and oversimplifies a very is high and Mg will then flow nesium in the diet during
blood magnesium depends complex situation. Trace into the bloodstream without times when conditions are
on the amount obtained from minerals such as copper, se- having to be pumped. High right for grass tetany. If the
the daily diet since the mag- lenium, and zinc are all es- magnesium mineral mixes active transport pump is
nesium present in teeth and sential nutrients vital for prevent grass tetany by in- driving magnesium across
bones is not easily mobilized proper growth, production, creasing the amount of di- the rumen wall, grass tetany
in times of need. Magnesium and immune system func- etary magnesium concentra- problems should not develop.
is required for proper nerve tion. Trace mineral deficien- tion in the rumen, allowing However, when factors pre-
and muscle function so low cies are very common and this passive movement of Mg vent this pump from working
levels in the blood result in predispose animals to seri- to take place. (for example, high levels of
“tetanic spasms” where mus- ous and sometimes fatal dis- Does Grass Tetany Only K+ in lush spring grass), the
cles contract uncontrollably. ease conditions. Commercial Occur in the Spring? No! second or “backup” pathway
The disorder in an adult cow trace mineral mixes are for- “Winter tetany” in beef cattle depends on increasing lev-
begins with separation from mulated to meet the needs is caused by consumption of els of magnesium in the diet.
the herd and going off feed. of cattle, including their a diet low in energy and an Supplementation with
The ears are often erect and daily need for salt. Because insufficient intake of magne- high magnesium miner-
twitching and the cow is alert, interactions occur between sium, usually over winter. It al should begin at least
hyperexcitable and may be all the various metals, min- may also be observed when 30 days prior to calving.
aggressive. The symptoms erals, and other elements in feeding wheat or rye baleage Cows require magnesium
quickly progress to muscle the diet, optimal amounts of since these forages are often daily or 4 ounces per day of
spasms, convulsions, diffi- all elements are essential for high in potassium and nitro- a 12% magnesium mineral
culty breathing, and death. proper nutrition. gen but low in magnesium. mix, especially during the
Often the affected animal is Several complex factors Affected cattle have border- late winter and early spring
found dead with evidence of are in play for magnesium line low blood magnesium if pregnant or lactating. The
thrashing and struggle on to be absorbed through the concentration then clinical keys to using a free-choice
the ground around her. De- rumen (stomach) wall and signs of grass tetany are trace mineral product are
ficiencies occur most often into the blood. Primarily triggered by a stressor such to ensure cattle have access
in beef cows when they are there is a “pump” mecha- as a severe cold snap. to mineral 100% of the time,
nursing a calf and grazing nism that actively moves the Hypomagnesemia is often use a palatable, quality prod-
young, green grass in early dissolved “soluble” form of referred to as an “iceberg”
spring. Fast-growing spring Mg across the rumen wall to disease because only a few continued on page 30
pastures are high in po- the bloodstream.
tassium (K+) and nitrogen If potassium in
(N+) and low in magnesium the rumen is
(Mg++) and sodium (Na+) high and sodium
ions. Affected cattle often is low, this setup
have low blood calcium con- changes the elec-
currently. Fall calving cows trical potential
may also experience grass needed to drive
tetany during the winter the pump. Re-
months. search has shown
Will Feeding Plain that the negative
White Salt to Cows Pre- effects of high po-
vent Grass Tetany? This tassium in early
claim is shared every spring spring grass can-
and, indeed, there are pro- not be overcome
ducers who do not have grass by simply adding
tetany that only feed salt. more sodium in
How can that be? Simply the form of salt.
put, for some producers, the In fact, too much
minerals available in their salt will increase
soils and forages are enough urination and
to meet the nutritional needs cause magne-
of their cows. Regional soil sium to be lost in