Lactating cows can eat upwards of 55 pounds of feed a day on a dry matter basis. How do they do that?  Ruminants produce large quantities of saliva every day. Estimates for adult cows are in the range of 25 to 38 gallons of saliva per day. Aside from its lubricating qualities, saliva serves at least two additional very important functions in the ruminant. It plays a major role in buffering the pH in the foregut and provides fluid for the fermentation activities in the rumen. Boluses of preliminarily chewed forage are regurgitated from the reticulorumen and re-chewed: the process we refer to as rumination or cud chewing. The grinding action of the teeth mechanically breaks down the plant fibers into smaller particles, providing additional surface area for digestive enzymes to “attack”. Animals on pasture or range typically graze for around 8 hours a day, providing a steady stream of feedstuffs to the reticulorumen. Contractions mix the feed around and between the rumen and reticulum. See Figure 1 for a diagram of a typical ruminant digestive tract.

outline of a cow with detailed labeling of the digestive tract: mouth, esophagus, reticulum, rumen, omasum, abomasum, small intestine, large intestine
Figure 1 – Illustration of the digestive system in a cow.

The rumen is essentially a fermentation vat. We have often heard cows have four parts to their stomach, the rumen in the largest section in this stomach series and tend to get most the attention because of its unique capabilities. It provides an anaerobic environment, constant temperature and pH, and thorough mixing that allow the microbes to digest forages. Bacteria, protozoa, and fungi are the three major types of microbes. Figure 2 illustrates the types and approximate numbers of microbe types in a rumen (and the number of humans on Earth, just for comparison). Mammals don’t produce enzymes that can digest plant fibers like cellulose. Cattle and other herbivores rely on the digestive enzymes produced by their gut microbes in order to get the majority of nutrients out of forages.

bar graph showing numbers of bacteria, protisis, fungi, mycoplasma, and viruses in a rumen. Also shown is the number of humans on earth for comparison. Data courtesy of Mel Yokoyana, Michigan State University.
Figure 2 – Illustration of microbe populations typically found in the rumen. The scale on the left is logarithmic.

The rate of flow of solid material through the rumen is quite slow and dependent on feedstuff size and density. However, water flows through the rumen rapidly and appears to be critical in flushing particulate matter downstream. As fermentation proceeds, feedstuffs are reduced to smaller and smaller sizes and microbes constantly proliferate. Ruminal contractions constantly flush lighter solids back around the reticulorumen while denser particles (feedstuffs that have been there longer) proceed to the omasum.

The function of the omasum is rather poorly understood. It may function to absorb residual volatile fatty acids and bicarbonate. The tendency is for fluid to pass rapidly through the omasal canal, but for particulate matter to be retained between the omasal leaves. Periodic contractions of the omasum knock flakes of material out of the leaves for passage into the abomasum.

The abomasum is a true, glandular stomach which secretes acid (significantly lowering the pH) and otherwise functions very similarly to the stomach of a monogastric. One fascinating specialization of this organ relates to its ability to process large masses of bacteria. In contrast to the stomachs of non-ruminants, the abomasum secretes lysozyme, an enzyme that efficiently breaks down bacterial cell walls. Much of the protein need of the ruminant is actually satisfied by digesting bacteria that have traveled from the rumen.

CRV USA is looking for qualified university students for two paid internships: a Dairy Genetics Intern and a Marketing Communications Intern. The Marketing Communications Intern will begin work as soon as January 2017 and the Dairy Genetics Intern during the summer of 2017.

To apply, submit a cover letter, resume, and sample work/project to by December 23, 2016.

Details are in the pdf links below.



OSU Calving School, Willamette Valley class

WHEN: Thursday, December 8, 2016, 4 pm to 8 pm

WHAT: This program will consist of presentations, educational videos, and simulated calving assistance. Topics covered will include The Calving Process, Nutritional and Management Strategies to Prevent Calving Problems, Designing Calving Facilities, Dystocia and Calving Assistance, Diseases and Injuries Associated with Calving, and Managing Newborn Calves.
(The program will have a beef cattle slant, but dairy cattle have calves the same way.)

WHERE: Oldfield Teaching Center (on west side of OSU campus)

COST: $20 per person (includes program, the calving school handbook, and pizza dinner)

PRESENTERS: Reinaldo Cooke (Beef Cattle Specialist), Shelby Filley (Regional Livestock and Forage Specialist), and Charles Estill (Extension Veterinarian)

For more information on the program, please contact or 541-236-3016

For on-line registration and payment, go to

If you need help registering, please contact the Linn County OSU Extension Service at 541-967-3871

Calving School will also be held in other locations:

December 9, 2016 (4 pm to 7 pm)       Myrtle Point, OR
December 12, 2016 (2 pm to 5 pm)     Fossil, OR
December 13, 2016 (4 pm to 7 pm)     Heppner, OR
December 14, 2016 (11 pm to 2 pm)   Enterprise, OR

For more information on those classes, please contact Reinaldo Cooke (541-573-4083) or your local Extension Office.

Welcome to the new Oregon State University Extension Service dairy blog, Dairy Bearing. The blog’s title might seem odd at first reading, but there’s a little more to it than the way it rolls off the tongue. (this is an internet-based medium, so forgive me for not pulling the print dictionary off the shelf), lists multiple definitions for bearing. They include

  • The manner in which one conducts or carries oneself
  • The act or capability of producing
  • The act of enduring
  • Reference or relation (e.g., having bearing on a problem)
  • Holding up or supporting
  • Moving in a particular direction

These definitions seem rather fitting if we think about them in the context of dairy farming.

The purpose of this blog is for us at OSU to share research results, techniques, resources, announcements, and other items that might be of interest to those involved in dairy production. Up above, there are permanent links that connect to various web pages that might be useful. This section that you’re currently reading will scroll along in typical blog fashion, with the most recent post at the top. Feel free to comment or post queries. Note that any comments not in the spirit of respectful discourse will be deleted.

And in the humor of the season:

Mother Goose and Grimm comic strip (2016-10-26) depicting vampires milking cows: "The Vampire Dairies".Mother Goose and Grimm