Usage of Hay in the Rabbit Diet

Nuances of Hay in the Rabbit Diet

Introduction

Hay is a widely recommended component in domestic rabbit diets, traditionally valued for its high fiber content and its role in maintaining dental and digestive health. However, the nutritional value, fiber type, particle size, and feeding strategy have a significant impact on rabbit wellbeing, growth, and longevity. This page explores the complexities and scientific findings behind hay usage in rabbit nutrition.

Fiber: Role and Digestion in Rabbits

Fiber plays a critical role in preventing digestive disorders and supporting gut health in rabbits. Reviews by Gidenne (1996), Gidenne et al. (1998d), and De Blas et al. (1999) emphasize the importance of dietary fiber—particularly indigestible fiber—in maintaining digestive motility and preventing gut stasis.

Recent work by Licois and Gidenne (1999) demonstrated that fiber also helps resistance against pathogenic agents. Furthermore, the initial health status of rabbits influences their susceptibility to digestive issues from low-fiber diets, with healthier rabbits experiencing fewer disorders (Bennegadi et al., 2000).

However, excessive fiber intake (over 25% Acid Detergent Fiber [ADF]) dilutes dietary energy, forcing rabbits to increase intake to meet energy demands. At very high fiber levels, rabbits cannot compensate by eating more, leading to reduced growth rates (Lebas & Gidenne, 2000).

Fiber Particle Size and Its Effects

Fiber particle size has significant effects on digestion, immunity, and mortality:

• Heterogeneous particle size in feed increases lignin content, reducing digestibility and potentially promoting digestive stress.
• Studies on New Zealand White crossbred rabbits show that optimal Neutral Detergent Fiber (NDF) levels combined with medium particle sizes (0.5–1.5 mm) minimize mortality rates (down to 0%) and reduce *E. coli* infections.
• Larger particle sizes correlate with increased leukocyte, eosinophil, and neutrophil counts, indicating an immune response linked to diet.
• Imbalances in particle size and fiber content increase digestive stress and disease susceptibility.

(Source: https://scialert.net/fulltext/?doi=pjn.2019.101.108)

Misconceptions About “Long Fiber” and Hay

Rabbits require both short and long fiber particles for gut health, but the term "long fiber" is misleading. Pellet fiber length is already sufficient for cecal fermentation and motility (Al-Khalaifah, 2019).

Excessive fiber intake above >24% accelerates gut transit time, impairing nutrient absorption and increasing the risk of digestive disorders such as mucoid enteropathy (Moore, 2022).

Additionally, excess indigestible fiber combined with protein encourages harmful bacterial overgrowth and ammonia toxicity by disrupting digestive microflora balance (Moore, 2022).

Hay contains lignin, which reduces protein and energy digestibility, increases stomach retention time, and raises the risk of functional impactions.

The coarse, loose fiber in hay is abrasive and can cause jaw stress and dental damage in domestic rabbits (Böhmer et al., 2017).

Common Types of Hay and Their Nutritional Profiles

Timothy Hay (Phleum pratense L.)

• Protein: ~3–13.8% DM (varies with storage and age)
• Fiber: ~31.8% DM
• Carbohydrates: 4.7–10.9% DM

Timothy hay is popular for fiber supplementation but cannot support adult rabbits alone due to low protein and energy digestibility. Its lysine content is low, meeting only about 70% of growing rabbits' needs. Calcium content is low (~0.33%), which can be either advantageous or limiting depending on the overall diet.

Alfalfa Hay (Medicago sativa L.)

• Protein: ~18.3% DM
• Fiber: ~28.6% DM
• Carbohydrates: ~4.5% DM

Alfalfa is highly palatable and widely used as a fiber and protein source. It promotes digestive motility and caecal flora balance. Inclusion recommendations vary but typically fall between 20–40%. High inclusion levels (>80%) have shown mortality reduction in some studies but may risk calcium overload in adults. Protein digestibility is moderate, limiting support for very rapid growth.

Red Clover Hay

• Protein: ~18.7% DM
• Fiber: ~27.4% DM
• Carbohydrates: ~13% DM

Red clover hay can safely replace alfalfa up to 30% without adverse effects on growth or mortality.

Oat Forage (Avena sativa L.)

• Protein: ~9.1% DM
• Fiber: ~34% DM
• Carbohydrates: ~17.7% DM

Grass Hay

Includes timothy, brome, orchard grass, tall fescue, bermuda grass.

• Typically high fiber, low protein, vitamins, and minerals compared to legumes.
• Nutritional content varies widely by species and harvest conditions.

Mixed Grass/Legume Hay

• Combines benefits of legumes (protein, minerals) and grasses (fiber).
• Balanced mixes (e.g., 1/3 grass to 2/3 legume) optimize nutrition and yield.

Bermuda Grass (Cynodon dactylon Pers.)

• Protein: ~9.8% DM
• Fiber: ~31.3% DM
• Carbohydrates: ~0.8% DM

Hay Quality and Storage Considerations

Hay quality varies drastically depending on forage species, harvesting maturity, drying, and storage conditions. Improper curing or storage increases risk of mold and nutrient loss. Compressed bales can harbor internal moisture and spoilage if not managed properly.

Pelleted feeds also risk contamination if stored in humid conditions but are generally easier to protect.

Feeding Recommendations and Balancing

• Balanced fiber content (around 18–22% NDF) combined with adequate protein (16–20%) and fat (3–4%) supports health and growth.
• Particle size should be consistent, ideally between 0.5–1.5 mm, to promote gut motility and reduce digestive stress.
• Hay should complement, not replace, a nutritionally balanced diet.
• Excessive fiber without sufficient digestible nutrients reduces growth and energy availability.

Summary

Hay remains a useful source of fiber in rabbit diets, but its role must be nuanced:

• Different hays vary widely in nutritional value and digestibility.
• Particle size and fiber composition impact digestive health and immune function.
• Excessive reliance on hay, especially poor-quality or high-lignin types, can reduce growth and cause dental strain.
• Balanced feeding of quality pellets is recommended for breeding and show rabbits.
• Proper storage and handling of hay are essential to maintain quality and safety.

References

• Lebas, F., Gidenne, T., et al. (2000–2004). Recent advances in rabbit nutrition. COST 848.
• Gidenne, T. (1996). Fiber digestion in rabbits.
• Licois, D., & Gidenne, T. (1999). Fiber and disease resistance in rabbits.
• Bennegadi, H., et al. (2000). Health status and low fiber diets.
• Villamide, M. J., et al. (2009). Alfalfa hay in rabbit diets.
• Grandi, F., et al. (1988). Red clover hay in rabbit nutrition.
• Reed, T.E. (n.d.). Hay feeding recommendations.
• [PMC Article on fiber particle size and mortality](https://pmc.ncbi.nlm.nih.gov/articles/PMC7054611/)
• [Scialert article on fiber particle size and immune response](https://scialert.net/fulltext/?doi=pjn.2019.101.108)