Photos of Rumen Development

This series of photos illustrates the process of rumen development in dairy calves.
Photos of Rumen Development - Articles
At birth, the rumen is small and undeveloped. By 4 weeks of age, if the calf is fed only milk or milk replacer, the rumen will still be quite small. In calves fed milk or milk replacer the abomasum grows in size, but the rumen remains relatively small. If grain is fed, the rumen grows much faster, as shown in the photo on the right.
At birth, the rumen papillae are short and inactive. During rumen development the papillae increase in length and thickness and begin to absorb volatile fatty acids (VFA) produced in the rumen. Calves use VFA as energy sources. Feeding grain stimulates rumen development more than feeding hay, which you can see here. Note the healthy, dark coloration and visible rumen papillae in the calf fed grain.
By 6 weeks of age, differences in the size of the rumen for calves on different diets are even more noticeable. The rumen of a calf fed milk only is considerably smaller than the calf fed milk and grain.
Here we can compare the rumen papillae development of 6-week-old calves fed three different diets. The calf fed grain from day 3 shows a great deal more papillae development and a much thicker, darker, and more vascularized rumen wall. In the calf fed good quality hay from 3 days of age, the papillae are not developed at all, and the rumen wall is quite thin.
The digestion of hay produces mostly acetic acid, which the rumen walls do not use for papillae growth and development. In contrast, fermentation of grains produces butyric and propionic acids that fuel the growth of rumen papillae. Both calves here exhibit dark coloration of the rumen and reticulum, but the calf fed hay has much less papillae development.
Both of these rumens are very large, but when it comes to rumen development size isn't everything!
In calves fed milk and grain the papillae grow larger and the rumen walls thicken as calves get older. In comparison, calves fed milk and hay until 12 weeks have very limited papillae development, and the rumen walls remain thin, despite the consumption of appreciable amounts of hay.
When we compare the rumen development of a 4-week-old calf on milk and grain to that of a 12-week-old calf fed milk and hay, we see the 4-week-old calf actually has a more fully developed rumen. Rumen development of individual calves fed milk, grain, and hay will vary from calf to calf depending on each calf's preference for dry feedstuffs.
The esophageal groove is a muscular fold of tissue that closes when calves nurse, allowing milk or milk replacer to bypass the rumen and enter the abomasum. Drinking water does not trigger the esophageal groove, so water ends up in the rumen where it aids in creating an environment for rumen microbes to grow.
The omasum absorbs nutrients. From these photos, we can see it is designed for that purpose, with many folds of very thin tissue. Because of these many folds, the omasum provides about one-third of the total surface area in the ruminant stomach.


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