On the Blog

Bouts of grass tetany could be just around the corner

Springtime can be a very busy time for most all cattlemen. When you look at the nutrients that are critical for spring calving herds, this can get very busy as well. As I write this blog, we are getting yet another dose of wet snow here in Western South Dakota. Looking forward, the 7-day forecast shows a good chance of precipitation most every day. While we can sure use the moisture, cattlemen need to be ready for grass tetany to rear up. Cool, wet springs generally increase the risk of grass tetany.

While there are many nutrients to keep your eye on in the next couple of months, magnesium could be the most critical if you have pastures that are susceptible to inducing grass tetany.


Rapidly growing cool season grasses will oftentimes not have enough available magnesium to support a cow’s needs. Cows are most vulnerable to grass tetany once they calve and begin to lactate, as their requirement for magnesium will almost double. Cattle cannot store magnesium, so you need to make sure your supplement provides magnesium to your herd, every day!


Many of you will still be feeding some moderate quality forages or grazing stockpiled forages in your pastures. Both of these situations would call for some supplemental crude protein to maximize digestion and release of energy from those forages. This is especially critical when meeting increased nutrient requirements for lactation demands in spring calving herds.

Trace Minerals

Calving and pre-calving nutrition should not skimp on trace mineral nutrition as trace minerals are critical to build quality colostrum for the new born calf. Immediately following calving, you are into the pre-breeding season and again, proper trace mineral nutrition is essential to get maximum breed-up from your cows.

Vitamins A and E:

Very similar to the reasons we supplement trace minerals, Vitamins A and E are essential to realize healthy calves and obtain maximum breed-up.


Phosphorus is generally lacking in most stored or dormant forages. A cow’s phosphorus requirements increase 50%-100% from gestation to lactation. We need to be thinking about supplementing phosphorus in the springtime.

Fly Control?

Although not a nutrient, fly control is certainly a consideration for many cattlemen in the spring. A good fly control supplement can pay back dividends as good as any other additive that is available in a supplement.

So, which is most important?

While all the nutrients or additives listed above are critical to your cow herd this spring, if you have pastures that have given you trouble with grass tetany in the past, Magnesium is by far the nutrient you need to focus on until that threat has passed. Cows can die from a shortage of available magnesium in a day or less. While other nutrients are certainly critical, their effects from a deficiency will not impact your herd as fast or intensely as a deficiency of magnesium. I’m often asked, “Which CRYSTALYX® product should I feed in the spring?”  If your pastures are prone to grass tetany, the answer is pretty easy – feed a product with a higher level of magnesium.

Fortunately, CRYSTALYX has a number of supplements which deliver higher levels of magnesium along with the nutrients and additives mentioned above.

Specific Products:

CRYSTALYX has a number of high magnesium formulas for many grazing situations: 

  • CRYSTALYX® Super-Mag™ is a Balanced magnesium supplement for general use. 
  • CRYSTALYX® Blueprint® 17 Mag is a premium magnesium supplement intended for situations where you need magnesium supplementation along with a total replacement of inorganic trace minerals with organic trace minerals to realize maximal performance from today's advanced genetics.
  • CRYSTALYX® ROLYX® Pro-Mag, would be the supplement of choice if you also want to add fly control to your magnesium supplement. 
  • CRYSTALYX® High-Mag Fescue-lyx® is a great choice if you are running cows on endophyte infected fescue.

CRYSTALYX is an extremely palatable supplement that is available to your herd 24 hours a day, 7 days a week during grass tetany season. With normal stocking rates (20-30 head per barrel) a set of CRYSTALYX barrels will last about 2 weeks. Whether it rains or snows, or while you are putting a crop in or are busy with other chores, CRYSTALYX is on the job, every day. And getting magnesium into your cows during the spring is definitely a job that needs to be done every single day.