The troublesome nature of rye grass for horses

Rye grass is popular among farmers due to its resilience and ability to withstand heavy grazing. However, for horses, this grass can pose several problems. While rye grass is beneficial for cows, it may not suit the dietary needs of horses, especially those with certain metabolic disorders.

How to identify rye grass

Appearance

• Green stems with narrow, blade-like leaves
• Grows in clumps with fibrous roots

Flowers and Seed Heads

• Spikelets holding flowers are attached alternately to the stem
• Seed heads have a single flower stalk with small white-to-brown flowers

Texture and Colour

• Moderate to fine-textured, soft to the touch
• Glossy, dark green leaves that are slender and sharply pointed at the tip

Grazing rye grass directly and the effects of high sugar and low digestibility

When horses graze directly on rye grass, the high sugar content can lead to a range of metabolic disturbances. These include laminitis, a painful and potentially debilitating condition, and exacerbated symptoms of pre-existing metabolic disorders. Additionally, low digestibility may contribute to undernutrition and digestive upset, manifesting as bloating, discomfort, and changes in stool consistency [2]. Horses grazing on rye grass may also experience a higher risk of behavioural issues due to the fluctuating energy levels caused by sugar spikes, and from discomfort as a result of excesses of lactic acid leading to acidosis in the hind gut environment .

Avoiding high-rye grass pastures

To avoid the negative impacts of rye grass, horse owners can implement several strategies:

• Pasture management: Regularly assess and manage the botanical composition of pastures to ensure a balanced mix of grasses.
• Alternative grass selection: Opt for grasses with lower non-structural carbohydrate levels and better digestibility profiles.
• Regular monitoring: Keep track of the grass’s growth stages and harvest hay at optimal times to maintain lower sugar levels [4].

Rye grass in fodder?

Research indicates that the digestibility of rye grass decreases significantly if harvested at a late stage of maturity for hay production. This mature grass contains higher levels of structural carbohydrates that are less easily digested by horses, potentially leading to issues such as inefficient nutrient absorption and even colic [1]. Moreover, the sugar content in rye grass is a particular concern. Horses, especially those prone to conditions like insulin resistance and Equine Metabolic Syndrome, may suffer from increased sugar levels in their diet [3].

The same issues that affect rye grass as fresh forage extend to its use in fodder. When rye grass is included in hay or haylage, especially if cut late, it retains high sugar levels and may be less digestible, posing similar risks as when grazed fresh [2]. This means that even careful pasture management may not be enough if rye grass-based fodder is used, as it can still contribute to metabolic and digestive issues.

Recommended grass species for horses

Instead of rye grass, the following species are recommended for horses, particularly those with special dietary needs:

• Timothy: Known for its favourable digestibility and nutrient profile [2].
• Native meadow grasses: These offer a variety of nutrient profiles and are generally more suitable for horses than rye grass [5].