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Calf rumen development: Is roughage beneficial?

A.F. Kertz for Progressive Dairy Published on 30 April 2021

Extensive calf rumen development studies were done in the 1950s, 1960s and 1970s at Iowa State University, Cornell University and the U.K. National Institute for Research in Dairying.

R.G. Warner in 1991 addressed rumen development in calves from a historical perspective. Key conclusions were:



  • Dry feed consumption initiates rumen development, which is well under way toward adult function by 2 months old.

  • Concentrates are at least equal to, if not more, stimulatory for papillae growth than hay.

  • Fermentation end products stimulate papillary proliferation in the order of butyrate, then propionate and then acetate.

  • The “scratch factor” of roughage has no impact per se on papillary development.

  • Hay consumption results in larger forestomachs, but at the expense of rapid growth.

  • Large forestomach capacity appears not to stimulate forage intake, and in fact, rumens will shrink to accommodate the feed the animal is consuming. The rumen does not act like a vacuum cleaner.

  • A consistent fermentation is needed to maintain the integrity of rumen papillae.

It was determined in several studies, such as by one of Warner’s graduate students in 1958, that “these data confirm the view that end products of rumen fermentation rather than the coarse nature of the feed are the stimuli for the development of rumen papillae.” In another Warner graduate student study, infused acetate, propionate, butyrate, glucose and sodium chloride at feeding time into two rumen-fistulated calves for 11 weeks until sacrificed at around 100 days old helped determine that volatile fatty acids stimulated rumen papillae development in the order of butyric, propionic then acetic.

After calves had been weaned early and fed a diet with either 90% concentrate or 90% hay, daily gains were 1.1 or 0.6 pounds (0.5 or 0.27 kilograms), respectively, with the latter calves described as being “thin, pot-bellied and unthrifty.” In 1959, Warner found that calves fed a milk diet had nearly the same rumen volume as calves fed a primarily starter diet – but with little rumen papillae length compared to the maximal papillae development on the starter diet (Table 1).

Calf remen development fed three different type of diets

While calves fed primarily hay had intermediate papillae development, they had much larger rumen volume, illustrating the pot-belly scenario.

Reduced daily gain and increased gut fill was demonstrated well by a 1966 British study (Table 2).


Effect of % hay in dry matter intake

They fed calves post-weaned diets with concentrates fixed at 1, 2, 3, 4 or 5 pounds (0.45, 0.9, 1.36, 1.81, 2.27 kilograms) daily with corresponding free-choice hay intakes averaging 61%, 31%, 25%, 16% and 4% of total dry matter intake.

Daily gain increased to about 1.3 pounds (0.6 kilograms) somewhat linearly along with corresponding rumen papillae development as concentrate intake increased. Maximal daily gains occurred at 16% and 4% hay in the total dry matter intake. But daily gain results were confounded as gut contents increased with increasing hay intakes. Thus, the best daily gains, rumen papillae development and least gut fill occurred with the highest concentrate and lowest hay intakes. Unfortunately, more recent studies with calf starters, in which hay is or is not fed, do not measure gut fill and implicitly assume there is no difference or that it is immaterial. Those are not safe assumptions.

The problem with feeding hay to young calves is that the volatile fatty acid production of rumen fermentation from hay is in the opposite order for rumen papillae development. Hay also is bulky and has a low and slow rate of digestibility, which leads to gut fill.

Ruminants derive their major dietary energy by absorption of volatile fatty acids produced in the rumen. These interrelationships are complementary and synergistic if fed and managed properly, as early feeding of hay to calves limits rumen development and true calf growth. The most recent National Animal Health Monitoring System study reveals a troubling picture in this regard (Figure 1).

Average days age within herd size when dairy producers first began feeding water


Dairy producers begin feeding hay too soon, while delaying the feeding of both water and starter. And the picture is worse for smaller herds.

Calf rumen development is dependent on volatile fatty acids produced in rumen fermentation in the effectiveness order of butyric, propionic then acetic. If hay is fed to young calves, then gut fill will likely occur and confound, if not limit or reduce, true bodyweight gain. Hay, straw or roughage also does not facilitate optimal rumen papillae development because of its unfavourable rumen fermentation pattern. end mark

References omitted but are available upon request. Click here to email an editor.

A.F. Kertz
  • A.F. Kertz

  • Nutritionist
  • Andhil LLC
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