Understanding SARA
Subacute Ruminal Acidosis (SARA) occurs when a dairy cow’s rumen pH drops below optimal levels, often without obvious clinical symptoms. Both confined and pasture-fed cattle are susceptible, as lush pastures contain high levels of digestible carbohydrates that can reduce ruminal pH. SARA is widespread in dairy cattle, affecting up to 33% during lactation, and up to 40% of pasture-fed cattle can experience rumen pH levels below 5.8.
Causes of SARA
SARA results from multiple interacting factors that lower rumen pH. Key contributors include:
- Starch concentration, source, and processing
- Forage fiber levels and particle size
- Use of buffers or alkalinizers
- Feed intake levels
- Pasture maturity and species
- Cow comfort and lying space
Because of these complexities, there is no single solution for SARA management. Instead, dairy producers should apply a combination of strategies to support rumen health.
Strategies for Managing SARA
1. Optimizing Forage and Fiber Intake
Cows naturally buffer their rumen by absorbing acids and through saliva production during rumination. Feeding more forage fiber and physically effective fiber (peNDF) increases chewing and saliva production, which helps neutralize acids. However, too much fiber can reduce feed intake and milk production.
Guidelines:
- Forage NDF should be between 17% and 23% to balance rumen health and feed efficiency.
- At least 50% of feed particles should be retained on the 8mm sieve of the Penn State Shaker Box to ensure adequate fiber intake.
2. Using Buffers
Supplementing buffers such as sodium bicarbonate, limestone, or calcareous algae helps stabilize rumen pH and can enhance milk fat production. Buffers also provide essential minerals and improve dietary cation-anion balance.
Recommendation: Include buffers at 0.25 to 0.50 lb/head/day if SARA is a concern.
3. Enhancing Cow Comfort
Comfortable cows spend more time lying down, which promotes rumination and saliva production. Overcrowding and poor stall conditions can reduce rumination and increase the risk of SARA.
Best Practices: Ensure clean, dry, and well-maintained lying areas to encourage rumination and overall cow well-being.
4. Improving Feed Bunk Management
Proper feed management is essential to prevent large meals and inconsistent intake, which can lead to rumen pH fluctuations.
Key Considerations:
- Provide consistent access to a well-mixed, balanced diet.
- Avoid sorting by ensuring uniform mixing of rations.
- Prevent overcrowding at the feed bunk to reduce competitive feeding behaviors.
Conclusion
SARA is a complex issue requiring a multifaceted management approach. By optimizing forage and fiber intake, supplementing buffers, ensuring cow comfort, and maintaining proper feed bunk management, dairy producers can minimize the risk of SARA while supporting overall herd health and productivity.
