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Problems with Rye and Fescue Grasses
Here is the physiology of “rye grass tetany” or “rye grass staggers” and then you can decide how to control your forage choices. The confusion is that we are talking of at least two separate issues, but with similar symptoms.
The first is a problem related to endophyte fungus in perennial ryegrass, the second is the issue of “electrolyte grass staggers” - or as it is sometimes called, “rye grass staggers”. Electrolyte refers to minerals found in the body, (sodium, calcium, potassium, calcium, magnesium, chloride, etc).
Endophyte fungus forms when the weather (humid and warm) allows growth of this organism on a particular type of grass. Growth of this fungus on perennial rye pasture has been well known (for many decades) to cause abortion and stillbirth in horses. We now know that a similar situation occurs with camelids.
The specific mode of action is not completely clear, but in the US, farms with expensive brood mares are very careful about this and only buy grass seed that are endophyte free. The problem is that the fungus is symbiotic and actually assists the growing grass. Thus, many seed merchants actually add in endophyte fungus and advertise it as such as a benefit.
Most of the grasses for sale at home centers have added endophyte or naturally have lots of endophyte (Kentucky 31 for example). Here is a recent review of this grass and the problem (crop.scijournals.org/cgi/content/full/41/4/1026).
Stillbirth can occur with little effect to the dam (or mare) but appears to be the result of interfering with progesterone synthesis and/or release. Without progesterone, the pregnancy cannot continue.
At high fungus infestation levels, the endophyte produces significant amounts of alkaloids or mycotoxins (lolitrem B, ergovaline and peramine) or other neurochemicals that will cause health problems. In particular, lolitrem B causes distinct neurological toxicity - staggers. However, these specific neurological problems are NOT from a problem with alterations in blood electrolytes.
Many of you are familiar with other mycotoxins - for example, the aflatoxin found in peanuts. Many people are violently allergic to this mycotoxin. Mycotoxins can also be found in moldy grain and in moldy forages. There is often a very distinct or “off” smell to moldy feeds. If your grain does not smell right, throw it away!
The issue of electrolyte staggers is of a blood mineral disturbance. Here is an excellent University of Nebraska site on this issue. (www.ianr.unl.edu/pubs/animaldisease/g32.htm)
There are many other websites that also describe this condition. Note that “hypomagnesemia” is a fancy word for low blood magnesium in the blood (hypo = low; the 'mia at the end means in the blood).
“Grass tetany” refers to inappropriate muscle contraction. This is a nutritional or metabolic disorder characterized by low blood magnesium, yet it is not just a simple magnesium deficiency. It is also called “grass staggers”, “wheat pasture poisoning” or “hypomagnesemia”. It primarily affects older cows nursing calves under eight weeks of age, but may also occur in young or dry cows and growing calves.
Grass tetany happens most frequently when cattle are grazing lush, immature grass, but it occasionally occurs when cattle are fed dry forages (“winter tetany”). High potassium and nitrogen content of grass seems to be associated with low blood magnesium. High nitrogen fertilization appears to reduce magnesium availability, especially on soils high in potassium or aluminum. Grass tetany occurs most frequently in the spring, often following a cool period (temperatures between 45 and 60°F) when grass is growing rapidly, but also is seen in the fall with new growth of cool season grass or wheat pastures.
Low blood magnesium may be caused by: 1) a diet low in magnesium, 2) a diet with nutrient imbalances that interfere with magnesium metabolism, or 3) higher levels of milk production. When blood magnesium drops too low, proper nerve impulse transmission fails, causing this tetanic or muscle disorder.
Some of us that grew up on dairy farms are very familiar with blood issues of this type – “milk fever” or convulsions are one issue. This is often seen in milk cows, where due to the lactational demands of a new calf, blood calcium levels drop and the muscles and nerves in the mother cow do not conduct properly. An IV shot of calcium gluconate to the cow immediate stops the problem (often within a minute) and in several more minutes, the cow will be eating grass once again.
Other websites also talk about high blood potassium (hyperkalemia) in rye grass staggers. This again, is due to the lush grass growth. Newly growing grass can have a high content of potassium and this too will cause problems due to high blood potassium. High blood potassium interferes with nerve conduction as well as muscle function.
So here is the issue to consider. Annual grasses (come up once and die) can cause electrolyte staggers if animals eat the lush growth (but not endophyte issues). Perennial rye grass (grasses that live year after year) can cause electrolyte staggers for the same reasons. But the perennial grass can ALSO cause fungus issues (endophyte problems). The two are closely related by have a VERY different pathophysiology.
Here is another example. In the late '90's, at the Alpaca Futurity in Oklahoma City, there was a problem with electrolyte grass staggers. Several animals died and dozens were treated. The issue was the sod in the pens. The sod was fresh fescue grass and the alpacas gorged on it. I think more than thirty (40-50?) animals were treated for the electrolyte problems. Our local farm veterinarian (not Tom) was the attending vet on call and he was a busy man testing and treating the animals. It was not a mold or endophyte issue and these possibilities were tested.
In seminars, we educate and warn alpaca owners of these two issues and we agree it is complicated. Thus, we are talking of "electrolyte staggers" and endophyte poisoning.
The key is to WATCH OUT for any animal that shows a wobbly head or has tremors on spring grass or on grass that is very moist and warm (that can promote fungus). Call your vet!
Note added: In agreement with many veterinarians, we now discourage the planting of ANY rye grass – annual or perennial. The advice used to be that annual rye was safe. Unfortunately, the quality control of annual rye grass is poor and lots of perennial seed is getting mixed in. If you want to plant a fall pasture grass, seriously consider using an inexpensive seeds (wheat, oats, etc) that are nutritionally the same as Orchardgrass (excellent nutrition).
Nutrition Overview
Nutrition Terms
Transfer Factor
Problems with Rye
Bermudagrass
Orchardgrass Choices
Alfalfa Forage
Nutrition Issues
Copper a Micronutrient