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4 'ideals' to promote rumen development at weaning

Olivia Schroeder for Progressive Dairy Published on 22 January 2020
Holstein calf

Everyone’s weaning process looks slightly different. Facility constraints or labor considerations might cause two farms with similar pre-weaning programs to look vastly different come weaning time. And, neither farm is wrong – each knows best what will work for them.

But no matter what your weaning program looks like, the focus should be on maximizing proper rumen development to avoid growth slumps and better prepare calves to transition into productive cows.



How can you make your weaning process more seamless? Where can you inch closer to the “ideal” weaning program for you? Here are four weaning program ideals to work toward:

1. The right calf age

Two or three weeks can make all the difference when it comes to rumen development and the calf physically being capable of dealing with weaning. No matter the level of nutrition a calf receives up to the point of weaning, a calf weaned at 6 weeks old often struggles in comparison to a calf weaned at 8 or 9 weeks old.

Why? Essentially, young calves metabolize carbohydrates in the lower gut, a function that decreases naturally at weaning. But, the switch to metabolizing carbohydrates in the rumen doesn’t start to increase until the calf is 8 or 9 weeks old, regardless of previous nutrition. Starter consumed before this time often results in gut fill versus true growth as the rumen isn’t ready to handle high levels of grain or fiber.

Calves at 8 or 9 weeks old have more capacity to consume and properly metabolize starter needed to meet nutritional needs. The physical size of the rumen is larger, the rumen microbiome composition is more diverse and mature, and there’s more rumen tissue available for absorption and metabolism of starter feed.

When calves are weaned too early, the result is often a gap in the ability of the gut to absorb and metabolize the starter feed, and calves often experience a post-weaning growth slump.


The microbiome of a 6-week-old calf is also very different from an 8- or 9-week-old calf. Research has shown that delaying the transition from a high-milk diet to an exclusively solid food diet (weaning) lessened the severity of change in the microbiome of calves. Calves weaned at eight weeks experienced a more gradual shift in microbiota versus calves weaned at six weeks who encountered a rapid shift.

2. A gradual transition (without sacrificing calf age)

Transitioning from milk intake to solid feed intake can be a bit of a shock for a calf, so the more gradually we can make it happen, the less of a shock it will be.

The ideal weaning transition would be to start slowly reducing the amount of milk or milk replacer and increasing the amount of starter intake for a period of 14 days, starting at 8 or 9 weeks of age. Fourteen days might not be possible for everyone, but even extending weaning a few extra days can make a big impact on calves.

The most important thing to remember: Don’t sacrifice weaning age for a gradual transition. A gradual weaning transition is good but not if it means you must start weaning before calves are ready. For example, if your goal is to have calves weaned by eight weeks, a 14-day weaning period doesn’t make sense because you’d have to start at 6 weeks of age, when the calf is less equipped to handle weaning.

man feeding cows

3. A nutritional balance

Whether you have a 14-day weaning process or a more abrupt transition, make sure calves have fully replaced the same amount of nutrition they were consuming through milk or milk replacer with starter before completely transitioning to an all-dry feed diet.


Consider, if you’re feeding milk replacer two times per day and jump down to one feeding per day during weaning, you’re cutting the total amount of nutrients the calf is receiving in half. It may take a couple of days for the calf to consume enough starter to make up the difference.

This is especially important for calves fed a full-potential diet (2.5 pounds of milk solids in 8-10 quarts of milk and/or milk replacer per day) before weaning. Calves are used to consuming a high volume of nutrition and should be consuming the same amount of nutrition via starter before completing the weaning process. While calves fed a full-potential diet will eat less starter early in life, they are able to rapidly increase starter intake at weaning due to their larger size and will eat as much or more at weaning compared to calves fed a lower volume of nutrition.

A more gradual transition allows the calf to slowly ramp up starter intake as milk intake declines, keeping the nutrient gap closer. A good rule of thumb is calves should be consuming 3 pounds of starter for three days in a row before being fully weaned.

4. A palatable, nutrient-dense starter

When calves start the weaning transition period, it’s important for them to have a palatable starter feed in front of them. Palatability drives intake, and intake is critical to help calves replace the nutrients they were receiving through milk.

Make sure the nutrient value of the starter complements the level of milk nutrition fed pre-weaning. If your milk replacer is more nutrient-dense, you want your starter to be nutrient-dense as well. For instance, if you’re feeding a high-protein milk replacer, you should use a high-protein starter to help avoid a post-weaning growth slump.

In addition to palatability and quality of the feed itself, starter feed management comes into play and can help drive intake. Make sure starter feed buckets are clean and that you are dumping out and replacing old, stale feed with new, fresh feed. A good rule of thumb is if you wouldn’t stick your head in the bucket and start eating, your calves won’t either.

At the end of the day, weaning is a simple concept with straightforward keys to success. Everyone wants to do what’s best for the calf, but it comes down to what you can do within the confines of your own system. Small steps towards the ideal can make a big difference, and your calves will thank you for it.  end mark

PHOTO 1: Starter intake should naturally increase leading up to the weaning process.

PHOTO 2: A highly palatable starter feed helps drive intake to avoid post-weaning growth slumps. Photos courtesy of Purina Animal Nutrition.

Olivia Schroeder
  • Olivia Schroeder

  • Senior Research Scientist
  • Purina Animal Nutrition
  • Email Olivia Schroeder