Article Summary:

Dairy cow’s rumen is the best mixing wagon, it breaks down the feed and generates energy. Dairy cows fed high-quality pasture has greater rumen size and water intake. Furthermore, milk production is not increased by pre-mixing the feed. Learn with how rumen size does not affect the feed intake.


A cow’s rumen is where the chemical process of breakdown takes place and energy is released as a result. The walls of the cow’s rumen move continuously and mix all the ingested feed.

Like all things with ruminant nutrition, take your time ruminating over this article to get the most out of it.

Understanding the dairy cows rumen has many incentives for dairy farmers. There are various myths surrounding the function of the rumen, today we explore and break down such myths.

In this article, we will understand the differences in the rumens of cows fed high-quality pasture in comparison to those fed total mixed ration. Later, we will discuss how rumen size does not limit the pasture intake and understand why rumen is called the best mixing wagon.

Without further ado! Let’s begin.

The difference in the Rumens: Pasture fed Vs Total Mixed ration

Now that we know what happens inside the rumen, let's take look at some differences that exist when pasture-fed cow’s rumen is compared with that of cow fed total mixed ration. There are three important differences:

  1. Water Intake
  2. Rumen Size
  3. Rumen Content

Let’s discuss them one by one.

1. Water Intake

High-quality pasture has a high water content, which makes it ideal for livestock.

Dairy cows have a larger intake of high-quality pasture, resulting in a higher water consumption. Estimates indicate that an average-sized cow consuming 18kg dry matter per day of high-quality grass has a daily water intake of approximately 100-120 litres.

It is clear that the faeces of these cows are loose in consistency and do not pose a health danger. The loose stool is just an indication of increased water content, a rapid pace of passage, and a rapid rate of ruminal turnover.

2. Rumen Size

Pasture-fed cows have a larger rumen size as compared with the rumen of cows fed on Total mixed ration (TMR).

Approximately 20-25% weight of pasture-fed cow is the rumen (big WOW of wonder!) while 10% live weight of cow fed total mixed ration is the rumen.

3. Rumen Content

The rumen content of pasture-fed cows is a big pool of mixed grasses without any layers that exists is rumen of cows fed total mixed ration. There are three distinct layers in the rumen of TMR fed cows. provides ration balancing features with pasture and supplements. provides ration balancing features with pasture and supplements.

Rumen size does not limit the intake of pasture

There is good news for every dairy farmer, dairy cows’ pasture intake is not governed by rumen size. In other words, there is no relationship between the gut capacity of a cow and its total intake of high-quality pasture.

There are, however, stretch receptors in the rumen, abomasum, and intestine. Research indicates cows that are fed high-quality pasture, their intake is governed by hormones and not the size or volume of the rumen.

The process of digestion releases hormones and thus signals the brain about three things.

  1. The nutrient content of feed intake
  2. Nutrient content of blood
  3. Cow’s reserved energy

The quality of feed drops when the neutral detergent fibre is greater than 50% and digestibility is below 70%. In this case, the gut capacity becomes influential.

Key Takeaway: Notice how the cow will sit down and stop eating after morning graze even though her rumen is not full? Precisely because rumen intake is not controlled by rumen size. So, don’t try to stretch the rumen as advised by some in the dry period.

The rumen is the best mixer wagon

The rumen is capable of mixing all the feed ingested by a cow. We can safely state that rumen is the best mixer wagon.

There is a myth told by many, who believe that rumen function is improved if all the feeds are mixed and intaken by the cow at the same time. This assumption is not supported by evidence.

No difference has been noticed in milk production by not mixing the feed, suggesting cow’s rumen is a near perfect mixing wagon.

On-going research in Australia indicated there was no difference in milk production of cows fed pre-mixed feed when compared to un-mixed feed.

Grazing cows were fed around 14kg DM/day of grass silage and wheat by mixing them. Their milk production did not increase when cows were fed the same feed from paddocks without mixing.

The benefit to Mixing the feed

The only benefit to mixing the cow’s feed before consumption is that every cow receives an allocated and balanced amount of forage and concentrate and thus avoid overconsumption of certain feeds that may pose a health risk.

You can read more on livestock ruminant nutrition here.

This brings us to the end of the article. Until we meet again, Happy Ruminating!

- The Dedicated Team of, 2022-03-29