Thanks Ross. It is good information, however in New Zealand we�ve found that
supplementing with Mg on its own, fixes both problems, provided there are
not other problems such as under or over-feeding or sudden changes of diet.
In animals and humans it has been found that excess Ca lowers the ability to
absorb Mg and ample Mg increases the absorption of Ca making supplmenting of
it seldom necessary.
Mg aids digestion, Ca uptake, and increases iodine uptake of the thyroid.
Many cows suffer so badly from low Mg that milk production can be lowered
throughout the lactation. Sunken eyes is a symptom. New Zealand AgResearch
in the 1970�s showed that, over a lactation, up to 15% more milk was
produced when adequate Mg was fed by spreading Mg oxide on pastures to be
grazed - even when cows were not showing a deficiency. After this
information was publicised feeding of Mg was widely adopted in New Zealand.
About 10% of people are slightly allergic to oxides (get nausea) so wear a
mask while spreading it. Mixing it with a good salt-based soluble mineral
mix such as Solminix reduces dust and increases animal consumption because
they like the salt flavour and dislike the bitterness of Mg oxide which is a
reason that self help Mg doesn�t work.
Grain is seldom fed in NZ so Mg can�t be added to it. Some supply Mg
sulphate and Mg chloride in the drinking water through a dispenser.
Mg sulphate is Epsom salts so can cause diarrhoea and too much Mg chloride
can damage the gut of animals.
GT can be brought on within a few days, irrespective of Mg levels, by any
sudden changes in weather, diet, suddenly stopping Mg, sudden hunger, or
even sudden changes of mineral supplements. All of these actions can
adversely affect the rumen flora causing a digestive upset and a drop in Mg
and Ca absorption, so sudden changes must be avoided. Even changing suddenly
from pasture to hay or vice versa can lower blood Mg levels and cause GT
within a few days. Don�t leave cows in paddocks or yards without feed or
water.
In some cases, the use of nitrogen can actually increase the Mg (and sodium)
content of herbage, but when potassium is high and nitrogen is applied,
metabolic problems frequently occur, especially if feed sodium and cobalt
levels are low.
Some researchers have suggested that low sodium levels impede the transport
of Mg through the intestinal wall.
Many pastures have K levels of close to 4% which is much too high and sodium
(Na) of 0.1% which is half what it should be. K at 2.8% is enough to get
good pasture growth and not cause too many animal problems, but few have it
this low.
Pasture samples sent to me from Wisconsin, Indiana and surrounding states
usually have about 0.3% Mg, but in New Zealand 0.2% is more common in winter
when the problems occur. It increases in summer. Adding Mg to fertilisers
can increase it to 0.25%, an increase of 25%.
Metabolic problems in well farmed New Zealand herds is about 0 to 1% of
cows. This is provided Mg is fed, which I'd estimate that 90% of our dairy
farmers do, but not all use the best Mg or supply it well enough.
Andre Voisin wrote about the benefits in the 1950�s in his book Grass
Tetany, but regrettably farmers in some countries still don�t know about
magnesium�s roll in preventing MF and grass tetany.
I recommend avoiding pastures with high legume content prior to calving,
then grazing them immediately after calving.
Animals are often found dead. Thrashing indicates grass tetany while none
could indicate milk-fever. The cause can be confirmed by collecting a urine
sample from the urinary bladder where the Mg level will be low. The Mg level
in the blood of down animals or about to go down with GT is low. Once down,
the blood Mg level can increase as Mg is drawn from the rest of the body,
especially from the muscles that are no longer being used, so to be
meaningful the blood should be measured before the animal goes down.
So the statement, �If the cow is down, draw a blood sample before treatment
is given,� needs correcting.
Ross, another small point. �Hypomagnesmia� is incorrect so someone searching
for hypomagnesemia would not find the page. You may like to inform the
writer.
On 2/11/06 5:05 PM, "Ross Gould" <srgould@shaw.ca> wrote:
> This is a link to a fact sheet from Tennis Marx, Beef Specialist,
> Production Systems, with Alberta Agriculture
> It deals with the problem of "winter tetany" a condition that sometimes
> occurs in beef cows wintered on mostly forage diets, especially when
> straw is the major roughage. It is caused by a magnesium deficiency,
> which is sometimes confused with milk fever because some, but not all,
> symptoms are similar. She gives a detailed summary of the symptoms and
> treatment.
>
> Tetany Problems in Beef Cows
> http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/beef4808
>
> Regards
> Ross Gould, P.Ag. Retired
> Calgary, Alberta
> P.S. I have a special interest in the issue because it was the focus of
> my M.Ag. retread degree in the mid '70s. R.G.
Best wishes,
Vaughan Jones
Hamilton
Waikato
New Zealand
