Grass tetany, caused
by magnesium deficiency does not seem to be a major problem in Oklahoma
although occasional cases are reported. It typically occurs in beef
cows during early lactation and is more prevalent in older cows. The
reason is thought to be that older cows are less able to mobilize magnesium
reserves from the bones than are younger cows. Grass tetany most frequently
occurs when cattle are grazing lush immature grasses or small grains pastures
and tends to be more prevalent during periods of cloudy weather. Symptoms
include incoordination, salivation, excitability (aggressive behavior towards
humans) and, in final stages, tetany, convulsions and death.
It is known that
factors other than simply the magnesium content of the forage can increase
the probability of grass tetany. High levels of potassium in
forages can decrease absorption of magnesium and most lush, immature forages
are high in potassium. High levels of nitrogen fertilization have
also been shown to increase the incidence of tetany although feeding protein
supplements has not. Other factors such as the presence of certain
organic acids in tetany-causing forages have been linked with tetany.
It is likely that a combination of factos, all related to characteristics
of lush forage are involved.
When conditions for
occurrence of tetany are suspected, cows should be provided mineral mixes
containing 12 to 15 percent magnesium and be consumed at 3 to 4 ounces per
day. It is best for the supplements to be started a couple of months
ahead of the period of tetany danger so that proper intake can be established.
Because tetany can also occur when calcium is low, calcium supplementation
should also be included. Symptoms of tetany from deficiencies of both
minerals are indistinguishable without blood tests and the treatment consists
of intravenous injections of calcium and magnesium gluconate, which supplies
both minerals.
Cows grazing
lush small grain pastures should be fed mineral mixes containing both calcium
and magnesium.
|
|
