Rumen health and efficiency


In the current context of increasing feed costs and the demand for sustainably produced safe and nutritional meat and milk products, improving animal feed efficiency has become critical for producers.

Rumen efficiency – the keystone of feed efficiency and farm profitability

The unique digestive physiology of the ruminant animal is characterised by the rumen, the first chamber of the digestive tract. The rumen is in essence a fermentation unit, harbouring an extensive microflora population which allows the ruminant to break down and utilise the complex carbohydrates found in plant material. This microbial fermentation provides the animal with energy in the form of volatile fatty acids (VFA) and protein from the synthesis of microbial protein that the ruminant can use for growth and milk production.

Rumen fermentation pathways


When feeding ruminants, we are in fact feeding the rumen microbiota. Studies have determined that the rumen microbiome influences feed efficiency through the production of VFAs. Many microbiome studies have also linked feed efficiency measurements such as feed conversion ratio (FCR), average daily gain (ADG) and feed intake to the composition of the ruminal microbiome.

To get the most from a dairy cow or feedlot animal, one must get the most out of the animal’s rumen “engine”. To increase the efficiency of feed utilisation, optimal rumen conditions must be maintained to support microbial fermentation and rumen function. Good rumen function will ensure optimal feed intake and digestion, supplying the animal with the necessary nutrients needed to support growth and production. On the other hand, poor rumen function will negatively impact feed intake, fibre digestion, health, and overall animal performance.

Challenges to rumen efficiency

Several factors can negatively impact rumen function and efficiency, and increase the risk of developing metabolic disorders, namely sub-acute ruminal acidosis (SARA). These include:

  • High plane of nutrition – diets fed in intensive farming practices typically contain high levels of concentrates, a source of readily fermentable carbohydrates.
  • Dietary transitions
  • Insufficient dietary fibre – small particle size and lack of effective fibre in feedlot diets or in lush spring pasture
  • Unbalanced rations and sorting
  • Variable pasture quality
  • Periparturient period: Physiological and behavioural changes occurring around calving
  • Environmental conditions: heat stress
  • Management – including transportation and feeding space
  • Mycotoxins

Ruminal acidosis

When fermentable carbohydrates in the diet are digested too rapidly bacteria will increase the production of VFA and lactic acid. When buffering capacity is reduced and the production of VFA exceeds the absorption capacity of the papillae, rumen pH declines.

Aetiology of ruminal acidosis

Different degrees of acidosis appear when the fermentation profile of the rumen is unbalanced by high levels of VFAs or lactic acid.

Sub-acute ruminal acidosis (SARA)

  • More common in dairy cows
  • Rumen pH < 5.8 for 3 or more hours within a 24-hour period
  • Causes mild diarrhoea, poor feed intake and laminitis

Acute acidosis

  • Less common, more severe, commonly occurs in feedlot animals
  • Rumen pH < 5.5
  • Usually associated with a drastic diet change
  • Clinical signs more prominent

Consequences of acidosis

Constant drops in rumen pH below 5.8 impair the growth and activity of the fibrolytic microbes reducing fibre digestion. Impaired fibre digestion reduces the energy extracted from the diet, reducing the energy available for muscle growth and milk production.

In dairy cows, SARA results in reduced milk production and reduced milk fat content. SARA damages the rumen wall, leading to papillae erosion, rumen wall destruction and increased permeability. The release of large quantities of lipopolysaccharides (LPS) and other inflammatory compounds such as histamines, is induced by SARA. These molecules can pass into the bloodstream causing laminitis, mastitis and increasing somatic cell counts (SCC) in milk.

In fattening animals, similar effects are observed with FCR and ADG being impacted. Rumenitis and rumen parakeratosis can cause bacteria (e.g., Fusobacterium necrophorum) to enter the bloodstream and proliferate throughout the liver leading to the formulation of liver abscesses. In severe cases, bloating and enterotoxaemia may occur particularly in sheep that were poorly adapted to a higher starch diet.


To get the most from a dairy or feedlot animal, you must get the most from the animal’s rumen. We can help you optimise rumen function and efficiency with our world-leading rumen-specific live yeast, Saccharomyces cerevisiae CNCM I-1077, brand name Levucell SC, developed by Lallemand Animal Nutrition. Levucell SC will help you get the most out of your herd, by ensuring optimal rumen function, digestion, and feed utilisation throughout your production cycle, even during challenging conditions.

Levucell SC has been validated in more than 100 publications for its beneficial mode of action in the rumen. The main effects attributable to this strain include:

  • Increased and stabilised rumen pH, reducing the risk of acidosis
  • Increased fibre digestion (↑ NDF digestibility in more than 364 different roughages) and subsequent improvement in digestibility)
  • A more anaerobic rumen environment

Levucell SC 20
  • Rumen-specific live yeast Saccharomyces cerevisiae CNCM I-1077.
  • Proven to improve rumination behaviour, rumen efficiency, rumen pH and diet digestibility, to support production even under challenging conditions.
  • Concentrated formula designed for use in meal feeds.

Levucell SC 10 ME Titan
  • Microencapsulated formulated designed for pelleted feeds and premixes.
  • Innovative TITAN® Technology ensures yeast survivability
Levucell SC 10 % Farm Pack
  • Diluted formulation for easy on-farm use


Nocek J. E. 1997. Bovine Acidosis: Implications on Laminitis. J Dairy Sci 80:1005-1028. Recent Application Technologies of Rumen Microbiome Is the Key to Enhance Feed Fermentation – Scientific Figure on ResearchGate. Available from: researchgate

Levucell SC 20
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Levucell SC 10 ME Titan
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Caitlyn de Vos

Caitlyn de Vos

Ruminant Development Manager