Managing for healthy rumen function

Maintaining rumen health

pH level

pH measures the acidity or alkalinity of a liquid. The correct pH in the rumen is essential for the survival of rumen microbes. pH affects the rumen as follows:

  • pH 6.2 to 7.0 - neutral to slightly acidic and ideal for all rumen microbes
  • pH below 6.2 - fibre-digesting bacteria slow down
  • pH below 5.4 - fibre-digesting bacteria die out, lactic acid bacteria increase, and acidosis results.

Summary of conditions in the rumen

Summary of conditions in the rumen

Cud chewing and rumination

Cud chewing produces enough buffers in saliva to maintain rumen pH. Cows produce about 100 L of saliva a day, providing water to the rumen, plus some minerals and natural buffers (including sodium bicarbonate to help maintain a healthy rumen pH).

A healthy rumen is dynamic and will contract 1-3 times a minute to keep contents well mixed.

Clean, fresh water

The moist rumen environment requires a large quantity of water. Cows will drink up to 100 L a day and should have access to water in paddocks, feedout areas and at the dairy.

Cows are particularly thirsty after milking. It is a good idea to provide water at the exit and entry points of the dairy.

Water intake is affected by water cleanliness and salt/mineral content.

If you wouldn't drink this, why should your cows?

If you wouldn't drink this,
why should your cows?

Effective fibre

The rumen requires longer feed particles (2-5 cm long) to:

  • stimulate cud chewing
  • stimulate rumination
  • produce sufficient saliva
  • reduce feed size for faster digestion.

Provide adequate but not excess fibre. Aim for 28-34% neutral detergent fibre (NDF) in the diet.

Consistent supply of nutrients

For optimal rumen pH and rumen microbe growth and activity, provide a consistent and constant supply of nutrients. Minimise feed changes and avoid slug feeding. For example, minimise the time between grain feeding in the dairy and access to forage after milking.

Rumen microbes can take up to 4-6 weeks to fully adjust to a change of feeds. Make any diet changes gradually. For example, if changing from ryegrass pasture to oats, make the change less abrupt by splitting into night and day grazings to build up the necessary microbe population.

A manure pat of ideal consistency with a dimple of top

A manure pat of ideal
consistency with a
dimple of top

Indicators of rumen health

Milk production and composition

Tanker dockets - plus individual cow and herd reports from herd recording - will show up any milk yield and composition variation. Any large variation in milk composition indicates an inconsistent diet. For example, a decline in milk fat below 3.3-3.5%, and a decline in milk protein by 0.25% units over 1-2 days may indicate rumen health problems. (See Nutrition and milk protein percentage and Nutrition and milk fat percentage ).

Farms that regularly check and formulate diets generally have less variation in diet quality and milk composition.

Number of cows ruminating

At least 50% of the herd chewing their cud when resting indicates good rumen health.

Manure composition

Check manure regularly for consistency and undigested feed.

Table 1. A guide to manure consistency
Manure consistencyMeaning
Normal manure well formed pat with dimple in top (See photo at right)
Thick, dry manure too much fibre
Liquid manure too little fibre
Bubbly manure hindgut fermentation of starch (an indication of acidosis)
Mucous in manure sloughing of lining of the intestines (an indication of acidosis)
Grain in manure passing too quickly through the rumen; possible lack of NDF; or grain not processed sufficiently for optimal digestion

Body condition

Body condition indicates overall herd nutrition, including healthy rumen function. Consistent body condition across the herd according to their stage of lactation indicates consistent feed management.

Ideally, cows should calve at a body condition score (BCS) of 5-5.5 (on a 1-8 scale), drop no lower than 4-4.5 BCS at peak lactation, dry off at 5-5.5 BCS, and maintain that condition throughout the dry period.