Grass tetany: Prevention is better than the cure
“We know our spring conditions in the northern Great Plains and Intermountain West are often favorable for grass tetany. Knowing that, it is always best to plan ahead in advance of green grass versus react,” said Montana State University-Bozeman beef cattle specialist Rachel Endecott of the importance of having cattle prepared to deal with lush spring grasses prior to turnout.
Magnesium is one of five major electrolyte minerals that must be fed to cattle in balance to one another for healthy body function according to J&R Distributing Nutritionist Peter Franzky of Lake Norden, S.D.
“When we have lush, springtime grasses growing rapidly on pastures, magnesium is not released by the plant at adequate levels. There is also a higher level of potassium released quicker from lush pasture grasses, resulting in an indirect deficiency of magnesium. So, we have to supplement magnesium to those cattle going on that lush pasture,” he said of the electrolyte mineral imbalance that results in grass tetany.
Supplement options available today range from loose mineral containing magnesium or adding magnesium oxide to loose salt to multiple supplemental blocks, tubs or liquid feeds containing an adequate percentage of the mineral.
“We want to feed a magnesium source to those cattle for 30-60 days prior to going onto pasture with a mineral that contains three percent magnesium and is consumed at a rate of four ounces per animal per day,” said Franzky of the percentage and consumption rate of loose mineral generally needed to keep cattle from contracting grass tetany.
In instances where cattle were not fed magnesium for 30-60 days prior to turnout, the percentage of magnesium in the mineral should be increased to 10-12 percent, with consumption remaining at four ounces per head per day.
Franzky added that molasses-based supplements should also include three percent magnesium if they are being used to prevent grass tetany in a herd.
“Typical consumption is also similar, although as with all free-choice feeds this is more art than science. But, in general they should be at four ounces per head per day when feeding begins 30-60 days prior to turnout. If a pasture is known to cause problems with grass tetany or they haven’t been fed for 30-60 days, then lick tub consumption should be increased to eight ounces per head per day,” said Franzky.
Regardless of what magnesium source a producer chooses to use, the most critical aspect is often ensuring cattle find it palatable enough to consume at necessary levels.
“The most important part of getting magnesium into cattle is finding a way they will eat it. This may take some experimentation to find out what your particular cowherd will eat at the necessary rate. I think each magnesium source probably has its advantages and disadvantages, but the biggest thing to be concerned with is if your cattle consume it,” said Endecott.
Providing the opportunity for cattle to continue consuming dry feed when they are turned out on pasture is another suggestion Endecott and Franzky provided that can help “dilute” the effects of lush springtime grasses.
“Put a bale of straw or hay the cattle are used to from their winter feeding program in the pasture and provide the cattle access to it. This enables them to fill up on that first, providing the rumen a certain amount of fiber-fill that will help prevent over-consuming green grass,” said Franzky.
Endecott added this might be an especially helpful management practice on years following a drought, where the percentage of old grass mixed in with new growth is reduced, increasing the chance of cattle contracting grass tetany.
“Cows in very poor body condition are also more susceptible to grass tetany. Keeping cows in good body condition, treating for internal parasite and coccidioses prior to going out to pasture are all additional important things producers can do to reduce the chance of their cattle getting grass tetany,” said Franzky.
However, as many producers can attest, despite taking a proactive prevention approach, the occasional instance of grass tetany can still occur.
“The symptoms of grass tetany include the cattle staggering and not having an appetite. In the worst-case scenario they will trip, fall down, and then cannot get back up. There is not a lot of time to save those, and in any case where a cow is showing symptoms time is of the essence,” said Franzky.
He suggested immediately calling a veterinarian upon finding an animal exhibiting symptoms. Treatment is the same as for milk fever, and includes drenching or intravenously providing the cow with a mixture of calcium, magnesium and glucose as an energy source.
“Any producer with previous grass tetany cases should contact his veterinarian ahead of turnout to make sure he has those products on hand in case they are needed,” said Franzky.
Endecott added the suggestion of moving cattle off a specific pasture into one with more old forage if possible, as an additional means of preventing further cases of grass tetany.
“Prevention is always the best plan when talking grass tetany. I suggest producers have a definite plan in place to get magnesium in cattle and prevent grass tetany in advance of green grass each spring, but to keep that plan flexible as the year develops,” she said .
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