Ryegrass is one of the best forage grasses available for cattle. It delivers high energy, high protein, and excellent digestibility, making it a top choice for both dairy and beef operations. A well-managed ryegrass pasture typically contains 20 to 25% crude protein, 11 to 12 megajoules of metabolizable energy per kilogram of dry matter, and 40 to 45% neutral detergent fiber. Those numbers put it in the upper tier of cool-season grasses for nutritional quality. That said, ryegrass does carry a few health risks worth understanding before you plant or graze it.
Annual vs. Perennial Ryegrass
The two main types used for cattle are annual (sometimes called Italian) ryegrass and perennial ryegrass. They suit different climates and grazing systems, but both produce high-quality feed.
Annual ryegrass is widely used as winter pasture in the southeastern United States. It’s typically planted in fall, grazed through winter and spring, then dies in summer heat. One of its strengths is that it holds productivity through the midsummer slump better than most other cool-season grasses. It does lack cold tolerance, so in the Midwest it generally won’t survive winter unless snow cover is reliable.
Perennial ryegrass is best adapted to mild, temperate climates. It tillers more heavily and stays lower to the ground than annual ryegrass, producing a denser sward. It’s considered one of the highest-quality forage grasses available, and it forms the backbone of dairy grazing systems in places like New Zealand, Ireland, and parts of the Pacific Northwest. The trade-off is that it’s more vulnerable to summer heat stress and doesn’t stockpile well for deferred grazing. It also needs good snow cover to survive cold winters.
Weight Gain in Beef Cattle
Stocker cattle on ryegrass pasture can put on impressive gains. Research from Mississippi State University tracked beef cattle over three consecutive years on annual ryegrass and recorded average daily gains of 3.15 pounds in year one, 2.92 pounds in year two, and 2.93 pounds in year three. Those are strong numbers for a grass-only system with no grain supplementation, and they reflect the high energy and protein content ryegrass provides during the cool season. For operations looking to add weight to stockers before finishing, ryegrass pasture is one of the most cost-effective tools available.
Milk Production on Ryegrass Pasture
Ryegrass is the foundation of pasture-based dairy systems worldwide, and for good reason. Its digestibility and energy density translate directly into milk. But not all ryegrass cultivars perform the same. A study comparing perennial ryegrass varieties found that cows grazing a higher-yielding cultivar (Bealey) produced an extra 0.9 kg of milk per day and 0.08 kg more milk solids per day compared to the trial average. Cows on a lower-performing variety (AberMagic) produced 1.5 kg less milk per day. That gap, roughly 5 pounds of milk per cow per day between the best and worst cultivars, adds up fast across a herd and a full lactation. Choosing the right variety matters.
Ryegrass Staggers
The most well-known health risk with ryegrass is a neurological condition called ryegrass staggers. It’s caused by toxins produced by a naturally occurring fungus (endophyte) that lives inside perennial ryegrass plants. The primary toxin, lolitrem B, interferes with nerve signaling at the muscular level, causing prolonged muscle activation that the animal can’t control.
Affected cattle develop muscle tremors, a stiff or spastic gait, lack of coordination, and in severe cases, collapse. Symptoms get noticeably worse when animals are exercised, startled by loud noises, or moved through yards. Between episodes, cattle can appear completely normal. Chronic exposure also leads to decreased feed intake, poor body condition, rough coats that don’t shed properly, reduced milk production, and heat stress.
The endophyte that produces lolitrem B also helps the plant resist insect damage, which is why it persists in ryegrass populations. Removing it entirely leaves the plant vulnerable. The solution has come through novel endophyte strains, particularly AR1 and AR37, which protect the plant from insects without producing lolitrem B. A multi-year study found that cows grazing AR1 or AR37 perennial ryegrass did not develop ryegrass staggers at all, and their total milk solids production over three consecutive lactations was no different from cows on standard ryegrass. If you’re establishing new perennial ryegrass pasture, selecting a novel endophyte cultivar eliminates this risk entirely.
Grass Tetany on Lush Ryegrass
Lush, fast-growing ryegrass pasture, especially in spring, can trigger grass tetany (hypomagnesemic tetany) in cattle. This happens because rapidly growing grass is low in magnesium and high in potassium and nitrogen, which interfere with the cow’s ability to absorb magnesium from its gut. Lactating cows are most vulnerable because they’re already losing magnesium through milk production.
The condition can come on suddenly. Affected cattle may show muscle twitching, staggering, and convulsions, and it can be fatal without treatment. Prevention is straightforward: provide oral magnesium oxide supplements during the danger period, roughly 60 grams per day for cattle. You can offer this as a topdressing on hay, mixed into a mineral feeder, or by dusting pasture with powdered magnesium oxide. Making sure cattle have access to hay alongside lush ryegrass also helps by slowing gut passage and improving mineral absorption.
Grazing Management for Ryegrass
Getting the most out of ryegrass pasture depends heavily on when you move cattle on and off. For annual ryegrass, the recommended approach is to begin grazing when the stand reaches 8 to 10 inches and pull cattle off when it’s grazed down to 2 to 3 inches. This leaves enough leaf area for the plant to recover quickly and produce another rotation of growth.
Grazing too low weakens root reserves and slows regrowth. Grazing too late lets the grass become stemmy and less digestible, which cuts both intake and nutritional quality. Rotational grazing, where you divide pasture into paddocks and move cattle through them in sequence, is the most effective way to hit those height targets consistently. It also gives each paddock adequate rest, which keeps the stand productive over the full growing season rather than declining after one or two grazing passes.
For perennial ryegrass, the same general principle of grazing down to 3 to 4 inches applies. Perennial stands are less forgiving of overgrazing than annuals, so erring on the side of moving cattle off a bit early protects long-term persistence of the pasture.