How to optimise the rumen for grazing

Managing the transition from winter feeds to fresh grass is crucial for dairy farmers aiming to make the most of grazing.

While grass is a cost-effective feed source, it’s important to handle the switch carefully to maintain cow health and ensure the rumen functions at its best.

The challenges of transitioning to grazing

When cows move from winter diets onto lush spring grass, the rumen undergoes significant changes.

Fresh grass differs substantially from conserved forage in its fibre content, sugar levels, and fermentability.

These differences can disrupt the microbial balance in the rumen, leading to increased acid production. When these acids accumulate faster than they can be buffered or absorbed, rumen pH begins to fall.

A sustained drop in rumen pH below the critical threshold of 5.8 is what defines sub-acute ruminal acidosis (SARA).

SARA can hinder efficient fermentation, resulting in reduced feed efficiency and poorer overall cow performance.

Without proper management, this shift in rumen conditions can significantly impact overall productivity.

How to manage rumen health at turnout 

According to Dr Colin Byrne, Ruminant Technical and Deployment Manager at Lallemand Animal Nutrition, the key to successful turnout lies in careful management and supporting rumen function through the diet during the transition.

Introducing cows to grazing slowly allows the rumen microbiota the time it needs to adapt, reducing the risk of pH fluctuations and supporting healthy fermentation.

Begin by allowing cows to graze for just a few hours each day, gradually increasing the time spent on pasture.

Over the course of 7 to 10 days, slowly increase grazing time each day, while monitoring their condition. Look out for signs of bloating, discomfort, or poor performance.

Supporting rumen function with live yeast 

To help support cows through the dietary transition, Dr Byrne recommends introducing the rumen-specific live yeast Levucell SC (Saccharomyces cerevisiae CNCM I-1077).  

This specific live yeast has been shown to stabilise rumen pH by supporting fibre-digesting and lactate-consuming microbes, helping cows cope with the dietary changes at turnout. 

Research has demonstrated that cows supplemented with Levucell SC spend significantly less time under SARA conditions.  

In trials, rumen pH dropped below the critical threshold for 240 minutes per day on control diets, compared to just 78 minutes per day when Levucell SC was included. 

For those supplementing grazing diets with concentrates, Dr Bryne adds that Levucell SC TITAN can be incorporated into compound feed formulations to maintain live yeast stability thanks to its patented micro-encapsulation technology. 

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