As we enter the spring season, livestock owners should be cognizant of some potential nutritional concerns related to fresh, young green grass.

Grass Tetany

Articles referenced: Grass Tetany, Carl R. Dahlen, Beef Cattle Specialist and Charlie Stoltenow, Veterinarian and Assistant Director of Agriculture and Natural Resources at North Dakota State University;
Grass Tetany/ Hypomagnesemia –Start Preventive Measures Now, Michelle Arnold, Ruminant Extension Veterinarian, University of Kentucky Veterinary Diagnostic Lab
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Grass tetany, or hypomagnesia, is caused by low blood levels of magnesium. It is most prevalent when cows and ewes that are in late gestation or heavy lactation graze lush spring growth, usually in April and May, but cases can be seen in the fall. Rapidly growing forages have low levels of magnesium, and the availability of magnesium is further reduced by high levels of protein and potassium in the forage.

Species most likely to cause grass tetany include cool-season grasses (crested wheatgrass, bromegrass, bluegrass and timothy), annual cereal grasses (wheat, rye, oats) and native range that lacks standing litter from the previous year.

Animals with grass tetany may experience excitable and erratic behavior. They can appear to be blind. Clinical signs can include hypersensitivity to touch, muscle tremors, frequent urination, staggered walking pattern, separation from the herd, convulsions, coma and, ultimately, death. The onset of the condition can be very rapid, and the first clinical sign producers may see is a dead animal.

Generally, veterinarians recommend slowly giving animals exhibiting symptoms an intravenous treatment with magnesium and calcium (which also is low in rapidly growing forage) in a dextrose solution. Contact your personal vet if you suspect grass tetany to discuss your unique circumstances.  In addition, if several cattle develop grass tetany in a pasture, consider the remaining animals at risk.

Grass Tetany Prevention Techniques

• Encourage daily intake of magnesium. Magnesium oxide is the most common source of supplemental magnesium. Supplementation with high magnesium mineral should begin at least 30 days prior to calving.
• Do not start grazing pastures too early in the spring; wait until new growth is 8 to 10 inches tall. Magnesium is more available in mature grass plants than in new, lush, growing shoots.
• Make sure lactating cows receive 0.20 percent magnesium in the diet on a dry-matter basis. This is equal to 18 to 21 grams of magnesium intake daily.
• Use salt mixtures containing magnesium oxide as a magnesium source. To be effective, the mineral mix should contain at least 10 percent magnesium.
• Mix magnesium oxide with other supplements because it is unpalatable (tastes bad).
• Graze legume or mixed legume-grass pastures first because early, lush grass growth is more problematic than legume mixed pastures. Note: Grazing unlimited lush growth of legume pastures can lead to cases of bloat. Take appropriate precautions if managing cattle on legume or legume-mixed pastures.
• Graze less susceptible animals on problem pastures. These animals include dry cows, heifers, stocker cattle and cows nursing calves more than 4 months old. Cows and sheep in heavy lactation are the most susceptible classes of livestock.
• Leaving sufficient forage in the fall will not only trap snow, retain subsoil moisture and reduce runoff potential, but it also will provide sufficient magnesium in the old growth to help balance the mineral profile and reduce the potential for grass tetany in the spring.
• Pastures fertilized with nitrogen (N) and potassium (K) fertilizers also are more likely to induce grass tetany. The plants’ uptake of nitrogen and potassium from the fertilizer further decreases the amount of magnesium available to the animal. Test the soils to ensure that nutrient rates in the fertilizer are not in excess of plant requirements for growth.

 Spring Laminitis (Founder)

Articles referenced: Prevent Spring Laminitis Now! Horseback, 1-10-14, Pete Ramey; Introducing Horses to Spring Pastures, PennState Extension; Laminitis in Horses, American College of Veterinary Surgeons
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Laminitis (founder) is inflammation of the lamina of the hoof and is a common in all members of the equine family: horses, ponies, donkeys, mules, and wild equids. It can be caused by any number of causes, including: grain overload, ingestion of lush grass, severe intestinal disease, sepsis, overweight bearing, inactivity, strenuous exercise, stress, and poor hoof conformation and maintenance. Regarding "spring laminitis", it is mostly caused by excess dietary sugars.

Spring pastures are very high in non-structural carbohydrates (NSC), including simple sugars, starch, and fructans. Horses are designed to eat non-cultivated grasses that are growing sparsely and are relatively low in sugar. If they get too much sugar in their diet, the byproducts of digesting that sugar can literally poison the horse. Additionally, the horse's body naturally creates more insulin to help process the excess sugar. The extra insulin circulating in the blood stream can weaken and damage the laminae, thus breaking down the bond of hoof to horse.

Horses experiencing laminitis may have excess fat on their neck, back and croup; hoof walls that are flare or a concave, bell shape; ripples or red stripes in the hoof walls; hooves with thin soles; and/or a shortened gait on hard surfaces. 

Spring Laminitis Prevention Techniques

• Routine hoof trimming needs to be a year-round habit. A good trim reduces these dangerous forces, and allows the sole, bars, frog, and hoof wall to share the load, thus reducing stress on the laminae. This can't stop the horse from eating too much sugar, but it can (and does) greatly reduce the damage that comes afterwards
• Wait until pasture grasses are at least 6 inches before turn horses out on spring pastures. Gradually introducing the horse to grass by starting with short periods of grazing each day.
• Practice proper range/pasture management and rotational grazing to prevent overgrazing and plant degradation.
• Manage dietary intake of additional sugars, such as grain, molasses, fruits, nuts, carrots, cookies and candy. A high-performance horse in training may need such calorie-dense supplements, but a maintenance-level pleasure horse may not. 
• Increase fitness and exercise. Unlike dogs and humans, horses have no way to shut off the continuous production of stomach acids that are an early part of the digestion process. Remember I mentioned that horses are designed to nibble almost constantly? A near-constant intake of forage naturally dilutes these acids. If you try to eliminate laminitis problems by denying your horse "chew-time," laminitis can be triggered when the horse's own "unused" digestive acids overflow into the hindgut. Too little feed can be worse than too much. Get out and ride, be sure your horse has room to move, and be sure your horse is living in a herd. Separate hay, salt and water to far corners of the pasture or paddock - anything you can think of to keep your horse more active. Increasing exercise is probably more important than reducing the dietary sugars, though at-risk horses will typically need both.

Grass is not the enemy

Grass is the horses' natural feed, and it is essential to them. Grass (and hay) should make up most of the horse's diet and be almost constantly available. It is our job to find ways to protect them from the risks associated with overeating and to provide missing vitamins and minerals, without adding excessive sugars in the process. Don't leave this to chance, take action.