Hi, I’m Dr. Ron Lemenager for Purdue University
Beef Extension Specialist, and what we’re going to do today is we’re going to a primer
on grass tetany for cow/calf producers. First of all, we need to talk about what is grass
tetany? It is a nutritional disease in beef cattle that has a common name of sometimes
grass staggers, lactation tetany, wheat pasture poisoning, winter tetany, but the bottom line
is that it is characterized by low blood magnesium levels in the animal. The question then becomes
what are the typical symptoms of grass tetany? Often times we find these animals dead out
in the field because the events of grass tetany often times take place from start to finish
within two to three hours. And what we’ll see in earlier stages of the onset of grass
tetany is animals that have trembling muscles, you’ll see twitching of the face, ear and
flank muscles. These animals are extremely excitable and as you look at them, they will
sometimes have a wild stare in their eye. They are typically uncoordinated. They will
have a stiff movement or gait. They will often times grind their teeth. In the later stages
they will go into violent convulsions and ultimately at the end of this process, you’ll
see the animal in a coma and it will often times be dead. So when does grass tetany typically
occur? It typically occurs in older cows with calves that are approximately two months or
younger. The logic here is that that happens when these cows are in their peak lactation.
It is typically not seen in the first calf heifer, although it is possible. We also see
grass tetany taking place usually on lush, early spring growth. Typically on cool season
grasses such as orchard grass, fescue and also we’ll see a grass tetany on fall seeded
small grain pastures like oats and rye and wheat when they are grazed in the early spring.
We’ll also see grass tetany take place 5 to 10 days after the onset of colder/wetter
weather. Now why is grass tetany a problem on lush, spring forages? Well part of the
problem is the plant itself, the grass plant. What we’ll see is reduced magnesium uptake
by the plant when we have the following conditions.: 1. High potassium levels in the soil, in other
words we’ve added a lot of potassium fertilizer. 2. When the nighttime temperatures are less
than 55 degrees Fahrenheit. 3. And this is all aggravated by high nitrogen
levels in the soil. Ok, so again, a fertilization issue.
That is a little bit counter to where we really want to be because, you know, you’d like
to be able to put on a significant amount of nitrogen early in the spring to promote
forage growth, and so this is a balancing act. Lush spring forages create complex interactions
that also affect the animal. For example, magnesium, which is really the mineral that
we’re concerned about in grass tetany, its absorption is reduced by high potassium intake,
low sodium intake, and higher fatty acid intake, and these are all characteristics of this
young, lush vegetative growth in the early spring of the plants that are high in potassium,
they are typically low in sodium and the fatty acid profile is a little bit higher. All of
these affect the magnesium absorption. The other problem that we have is that energy
absorption is also reduced in the animal because of the high soluble protein intake caused
by eating this lush vegetative plant and low soluble carbohydrate intake that is associated
with that plant. Now, a cow with symptoms of grass tetany is really an emergency situation.
It requires early detection and treatment immediately upon discovering the event. What
we need to do as producers is then is you need to call your herd health veterinarian
immediately when you find a cow that you suspect having grass tetany. What the veterinarian
will do is they will give an intravenous infusion of calcium and magnesium typically in a dexterous
solution, you know to bring these cows back out of that. And the recovery, if found early
enough with this treatment is pretty successful. The problem is, remember we only have about
a 2 to 3 hour window from the onset to the time that these animals typically die. So
our timing is really critical. When you think about moving or handling these animals, make
sure that you do it extremely carefully, because these animals as we indicated earlier are
very excitable and any excitement that you add to that animal will add stress and it
could cause sudden death. The ultimate goal in grass tetany is its prevention. The grass
tetany season is usually typically in that very early growth of the plant, typically
in April and May and what we need to do as producers is we need to give some consideration
to using some higher magnesium containing mineral supplements and these supplements
need to contain some salt. Salt will improve magnesium absorption and the intake of that
magnesium component in that mineral. One of the things we need to understand is that typically
the magnesium compounds like magnesium oxide is not very palatable and so we need something
to enhance its palatability and salt is one of those things. It will do that. We also
need to think about what the cost of this is going to be and for a 60 day early spring
grazing season, the total mineral cost for all minerals that you are going to add would
be something in the order of 5 dollars or less. The other thing we can do during the
grass tetany season is to supplement with energy and one of the common recommendations
is to either add corn or dried molasses or something that would increase the palatability
of that magnesium-containing mineral. Okay, so you’re adding energy right to the mineral
itself. The alternative to that is to add hay or corn, or some other high energy feed
when the grass is what we call washier. It is extremely high in water content typically
when the grass is in that stage of the first 6 to 8 inches of spring growth. The other
thing that we need to think about as producers is to avoid adding high levels of nitrogen
and potassium to the soil or having a high nitrogen and potassium soil content or analysis.
Now what are some of the feeding considerations for when we put mineral out for the cows?
Well first of all, if we are going to have a magnesium-containing mineral out, intake
is extremely important. That means we need to put the mineral feeders in the correct
areas where the cows are going to use it. We need to have enough feeder space available
for the cows, typically 15 to 20 cows per mineral feeder so that all animals have ample
opportunity to consume mineral. We need to keep the mineral fresh, in other words, if
we’ve got mineral in a feeder and it gets rained on or whatever and it starts to cake,
mineral consumption will go down so we need to think about adding mineral more frequently
to keep it fresh instead of putting out a week supply or a month supply at a time. The
other component of this is that typically we will see increased intake when we use mineral
in its loose form compared to having a block form of mineral. One common form of on-farm
mineral mix that we could use about 25% dical, 25% trace mineralized salt, 25% magnesium
oxide, and 25% of an energy source and palatability enhancer, and that palatability enhancer/energy
source could be ground corn or dried molasses. Now to wrap this up one of the things that
producers need to give serious consideration to is good year-round mineral supplementation
program. It is important for a variety of reasons. One of the things that we know is
that mineral requirements change during the growing season as forage quality changes and
also as cows go through different stages of production, in other words, peak lactation,
you know, end of the dry period, etcetera. The body can store some vitamins and minerals,
ok, for use at later times. So, if we’ve got a good mineral program and the body stores
are adequately created, when we get into a high demand time, some of those vitamins and
minerals can be pulled from the body stores and offset some of the problems we might have.
We can’t rely totally on body stores, however. We have to provide minerals adequately during
the course of the year and obviously minerals are important from the standpoint of herd
productivity, not only for the preventative of grass tetany, but also in the areas of
fertility, conception rate, weaning rates, the milk production of these cows, gain and
feed efficiency and also in the immune function of disease resistance, particularly of the
calves and how those animals respond to vaccines etcetera, so that kind of wraps grass tetany
as a whole primer for our cow/calf producers. Thank you and have a good day.