There are some things that you will need to take into consideration before you let the cows out to graze to prevent any health problems from occurring:
What is grass tetany?
This is a metabolic disease that is caused by a deficiency in the mineral Magnesium. It generally occurs during early spring when grasses experience a rapidly growing phase.
During this stage of growth they do not provide much of the amount of Magnesium that cows need. Also in this stage it will have a very high moisture content meaning that they will have to consume even more of it in order to meet their Dry Matter intake requirements.
One of the clinical signs that occurs with this disease is increased irritability. The cow may also go off to graze by itself and be staggering around along with muscle twitching. A problem with diagnosing this particular disease is that any clinical signs may not be fully visible. In some occasions it hits so rapidly that by the time you have any idea that it is occurring you have a dead cow.
Causes
As I mentioned in the section above it is normally caused by a deficiency of Magnesium in the blood. Since the grasses are growing very rapidly they do not provide a lot of nutrient value.
Risk of grass tetany can increase in lush, green pastures that are also high in potassium and nitrogen. These two can tie up the magnesium in the plant preventing it from making it to the growing part. They can also interfere with the magnesium being absorbed in the rumen.
The stage of production can also have an impact on the risks involved. Since cows are lactating their body’s demand for calcium is also increased. The need for calcium will tie up any absorption that will occur. This increase could result in more severe cases of grass tetany.
Harsh or extreme weather that can prevent cows from feeding for 24-48 hours can also increase the risk of grass tetany occurring.
Prevention
Now that we have discussed what grass tetany is and some of it’s causes let’s talk about some ways that you can prevent it.
The general rule of thumb is to provide a mineral or lick tub with an additional Calcium and Mg. This will provide a way to replace anything missing in the diet. According to the Veterinary Quarterly Review by the Texas AgriLife extension service you should begin provide the supplement 30 days before tetany is observed. Usually this means either in late winter or early spring.
It is also recommended that you increase the energy and roughage intake of your cows. As mentioned earlier during this time of year grass is nearly 75% water so any nutrients that it may provide will be severely watered down. The key here is to make sure that her Dry Matter intake is being met.
If your cows are in the beginning stages of grass tetany any extreme stress can increase the severity. That is why it is recommended to work the cows slowly and quietly in order to eliminate any unnecessary stress from occurring.
Options
There are a few options out there that you can use to prevent and treat any case of grass tetany that occurs. The best way to go about it is to talk with your vet to see what steps or treatments would be best for you.
Ok, now that we have the disclaimer out of the way here are a few options you could go with.
The simplest option is to provide a mineral supplement to fill in any missing gaps. You will want to make sure that the supplement that you are using has at least 8%-12% Mg. This will provide what she needs to keep this disease away as well as the other nutrients that she needs. I discuss the importance of a mineral supplement here.
One option that you can go with is to plant legumes in the pastures that your cows will be on this time of year. Legumes are a good source of Mg and calcium and they will provide the dry matter that she requires.
If the water in the pasture is in a controlled state such as a stock tank or trough a Mg salt treatment may be an option to go with. Choosing the correct form of magnesium is very important if you decide to go with this option. Some forms do not dissolve in water so that would be something to find out.