The Hidden Dangers of Lush Green Pastures

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Winter is finally giving way to warmer weather, which means lush, green pastures for livestock to enjoy are just around the corner. However, these lush pastures are often very high in moisture; therefore diluting their nutrients. The result is that animals have a difficult time consuming enough to meet all of their nutrient requirements. Two unrelated, but equally important problems are commonly seen during the early grazing season – grass tetany and pasture bloat.

Grass Tetany

Grass tetany, commonly referred to as ‘grass staggers’, is a metabolic disorder caused by a deficiency in magnesium (Mg). Livestock are most susceptible to grass tetany during early lactation, when milk production is at its highest, or when they are older and less capable of mobilizing Mg reserves in their bones. Grass tetany is typically seen in late winter and early fall (February through April) when animals are grazing on cool-season grasses (ex: tall fescue, orchardgrass, annual ryegrass) and small grains (ex: wheat, oats, barely, rye) during cool, cloudy and rainy weather followed by a warm period. The greatest risk of grass tetany is usually found in pastures grown on soils that are low in available Mg, but are high in potassium (K) and nitrogen (N).

Clinical signs of grass tetany include: not grazing, nervousness (staring and keeping their heads and ears in an erect position, or lying down and getting up frequently), muscle twitching and ‘staggering’ while walking. An affected animal may go down on its side and experience muscle spasms (periodic foreleg paddling, twitching of the eyes and ears) and convulsions. An affected animal usually dies during or after a convulsion unless treatment is given.

Treatment should be given in the early stages of grass tetany. Cattle or goats that are down longer than 12-14 hours have a slim to none chance of survival. A 20% magnesium sulfate (Epsom salt) solution can be given subcutaneously (under the skin) treatment. Blood Mg levels can be increased within 15 minutes by intravenously administering 500 ml of calcium borogluconate solution with 5% magnesium hypophosphate. The solution must be administered slowly, and heart and respiratory rates should be monitored closely during administration.

The best treatment for grass tetany, however, is prevention. Pastures grown in soils that are low in both Mg and pH should be limed with dolomitic lime, which contains high levels of Mg. Legumes (ex: clovers, lespedezas) often contain high levels of Mg naturally, and may help reduce the risk of grass tetany when included in forage programs. However, the most reliable method of prevention is supplemental feeding of Mg and calcium (Ca) one month prior and during grass tetany season. Look for mineral mixes that include 2.5-3.5% Mg to add to feed rations.

Pasture Bloat

Bloat is digestive disorder characterized by an accumulation of gas in the first two compartments of a ruminant’s (cattle, sheep, and goats) stomach. Gas is a natural by-product of ruminants’ digestion, and is usually relieved by eructation (belching). Pasture, or ‘frothy’, bloat, results from the production of a stable foam that impairs the animal’s ability to relieve these gasses, thus causing the rumen to expand and compress the lungs. Once this happens, the oxygen supply will be cut off and the animal will suffocate, sometimes in as little as an hour.

Bloat can be caused by grazing animals on lush pastures – typically ryegrass or small grains – that are low in fiber and highly digestible, but bloat is most commonly seen in animals grazing on immature legume pastures, specifically clover and alfalfa. Other legumes, such as arrowleaf clover, berseem clover, sericea lespedeza, annual lespedeza, and crown vetch, contain leaf tannins that help to break up foam. However, some animals, such as ‘aggressive-feeders’, are more susceptible to bloat than others.

Clinical signs of bloat include: rapid swelling on the left side and signs of discomfort, such as kicking at their bellies.

Catching bloat in its early stages often yields the best results. Bloat can occur in as little as 15 minutes to an hour; however, there is usually a 24-48 hour lag before bloating occurs. Immediately remove a bloating animal from the bloat-inducing pasture and offer them dry hay. This will reduce the bloat problem in all animals that will eat. Forcing bloated animals to walk can increase belching. Remember to handle bloated animals gently since their breathing is impaired. If this does not lessen the bloating, then you can try to manually release the gas by: 1) stomach tubing – this involves restraining the animal and passing a rubber hose down the esophagus. 2) Trocar – this is a device that punctures the rumen from the outside and is a rapid and effective means of releasing the gas. This should be used as a last resort as animals treated with a Trocar will require antibiotics to prevent peritonitis (a potentially deadly inflammation of the abdominal lining).

Just like with grass tetany, prevention is the best treatment for bloat. If your pasture is predominantly legumes, like clover, consider over-seeding your pasture with a cool-season grass, like tall fescue or orchardgrass. Bloat has very rarely occurred in pastures that are a 50/50 mixture of grasses and legumes. Do not turn out shrunk or hungry animals on lush legume or small grains pastures without feeding them hay or supplemental grain. Finally, invest in anti-bloat products with poloxalene in them. Poloxalene is an anti-foaming agent that prevents bloat for 12 hours by breaking down stable foam. A good, easy-to-use source of poloxalene is a saltmolasses block – there are 30 grams of poloxalene per pound of block. To use, remove other sources of salt, and replace with poloxalene blocks – 30 pounds per 4-5 animals (cattle) – at least 3 days before placing animals in pastures with significant bloat risk.

Again, if you suspect either of these conditions it is recommended to contact your vet immediately.

Happy grazing, ya’ll!