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Rumen development: Slow and steady wins the race

Troy Wistuba and Tom Earleywine for Progressive Dairyman Published on 06 May 2019

Think of calf rumen development as a journey. Calves transition through nutritional stages – from milk to starter and grower to TMR. What’s being fed at each of those stages impacts rumen development.

At the finish line? Heifers enter the milking herd with better feed efficiency, higher capacity for dry matter intake (DMI) and, ultimately, produce more milk.



The Rumen Journey

While your first instinct may be to reach the finish line as quickly as possible, skipping steps or pushing too fast can put heifers behind and impact future profit potential. The rumen development race calls for more of a tortoise approach than the hare.

Get your heifers to a profitable finish line with these guidelines for efficient rumen development:

Growing the calf

Preparation is key to winning any race. You can’t just dive in and expect to come out on top. The same goes for rumen development. The first step is preparing calves to handle a large-capacity rumen down the road.

The rumen is the size of a softball at birth and grows 150 percent in the first eight weeks of life. Feeding a full potential milk diet of 2.5 pounds of milk solids in 8 to 12 quarts of milk or milk replacer is the foundation for developing well-grown calves capable of handling an efficient, high-capacity rumen.


When it comes to feeding starter or hay at this stage, remember slow and steady wins the race. The rumen is still developing and isn’t ready to handle high-fiber diets. Calves fed less milk early in life may have more starter intake initially, but the result is gut fill versus true growth and rumen development.

Start by offering a handful of high-quality calf starter in a shallow bucket on day 3 of life and gradually increase the amount. Focus on calf growth through the milk diet, and starter intake will take off as their frame and rumen capacity develop.

Ramping up starter intake

Preparation in the milk-fed phase pays off as calves transition through weaning. Well-grown calves have well-grown rumens with the capacity to handle an all-dry-feed diet. Starter intake is a good indication of when the calf (and the rumen) is ready for weaning.

Take a lesson from Goldilocks when you think about starter intake. You don’t want too little or too much, but just the right amount of starter intake. Low intake can indicate too much fiber in the diet which the rumen can’t yet accommodate. High intake can mean the rumen is underdeveloped. Calves overeating are trying to compensate for lack of nutrition in the milk diet. Overeating can result in gut fill, scours or rumen acidosis, which can cause calves to lose traction on rumen development that can’t be made up later.

Well-grown calves will naturally increase the amount of starter consumed as they approach weaning. The sweet spot is 3 pounds of starter for three consecutive days before beginning the weaning transition.

Developing the papillae

In the post-weaning phase, underdeveloped calves start to fall behind, while well-grown calves move on to the next stage of the race. Rumen volume continues to expand post-weaning, but now attention turns to developing the rumen papillae.


Papillae increase the surface area of the rumen to help boost nutrient absorption. Think of papillae as a layer of carpet across the rumen surface – the thicker, the better. Starch in the diet increases rumen fermentation which produces volatile fatty acids (VFAs), which in turn encourages papillae growth.

Feed a starter with 6 to 10 percent fiber and 22 percent protein post-weaning through 12 weeks to support continued heifer and rumen growth and papillae development. Hold off on hay or high-fiber feeds that can restrict intake and stall growth.

Finishing strong

The final leg of the rumen development journey begins around 12 weeks old when heifers are eating 10 pounds of starter per head per day. Rumen volume and papillae growth are on their way to full development but need a final push to make it to the finish line.

Switch to a grower feed and incorporate high-quality hay into the diet to help complete the rumen development process in a cost-efficient way. Grower feeds are less nutrient-dense than starter yet provide the nutrition heifers need to maintain growth and papillae development.

This grower intermediary step between starter and TMR is essential to avoid growth slumps and reach breeding weight on time. Forages grown on-farm are often inconsistent, upsetting the rumen environment and causing heifers to go off feed if the rumen isn’t fully developed. Grower helps keep the total diet more consistent.

The rumen development journey ends at around 5 months old or 450 to 500 pounds. The rumen is fully developed and can handle a more variable feed source such as TMR. A well-grown, properly fed heifer should enter the milking herd with a 40-gallon rumen machine, ready to efficiently turn large amounts of feed into profit in the bulk tank.

One of the most helpful pieces of any race is your team, working side by side to help you reach the finish line. Your local calf and heifer specialist is an essential team member to help you and your calves through each stage of the rumen development race.  end mark

INFOGRAPHIC: Infographic courtesy of Land O’Lakes.

Tom Earleywine, Ph.D., is director of nutritional services with Land O’Lakes Animal Milk Products. Email Tom Earleywine.

Troy Wistuba