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Readiness to wean

Amanda Kerr and Emily DeBenetti Published on 22 May 2015

Beyond the neonatal phase, calves face another large metabolic shift and a drastic leap in their development at weaning, where specific feed and housing management are again factors to be closely tailored to these animals’ needs.

Transitioning from one feed type to another should be done at an age and in a fashion to allow for development and proper function of the digestive mechanisms and microbes the calf will rely on for feed breakdown.



With this in mind, in 2014 the Grober Young Animal Development Center (GYADC) investigated readiness to weaning age at 7 or 10 weeks with two different pens allocated to each weaning age (n = 50).

Weaning was over a 10-day step-down program, reducing intakes by 0.4 L per day with an allotment of 2 L offered on the final day. Feed intakes, bodyweight gains, blood ketone levels and visits to the feeder prior, during and after weaning were used to gauge weaning success.

A collaborative study was conducted at the GYADC with Hana Brown and Dr. Ken Leslie of the University of Guelph. This experiment entailed testing a drop of whole blood for the beta-hydroxybutyrate (BHB) levels, using the calf-side Precision Xtra test, before and during weaning.

The objective of the study was to determine if blood BHB levels were predictive of the readiness for weaning, according to rumen function, which is an important factor for successful weaning. As the rumen develops, microbial populations increase, generating volatile fatty acids (VFAs) from the fermentation of solid feed. The VFAs diffuse through the lining of the rumen and should be recognized as ketones (BHB) in the blood.

In this experiment, calves weaned at 10 weeks showed significantly greater and more consistent average daily gain (ADG) and expressed less frustration behavior versus the calves weaned at 7 weeks (Figure 2 and 3).


The later-weaned calves consumed more grain as a percentage of bodyweight (Figure 1), which corresponded to their increased weight gain during and after weaning (Figure 2). The larger intakes of dry feed also represented an improved ability to digest this form of feed, consistent with a more mature level of function in the gastrointestinal tract of these calves.

grain intakeaverage daily gain

This observation was reflective in the blood BHB results, where 10-week-old calves had higher levels of BHB leading up to and after weaning. These calves also had fewer unrewarded feeder visits (Figure 3), suggesting a link between decreased frustration with being weaned off milk and a greater eagerness to consume grain as an effectively utilized energy source.

unrewarded visits

Measuring grain intake as a percentage of bodyweight and using automatic feeder technology can be useful tools when judging a calf’s biological readiness to wean.

Calves eating a minimum of 1.6 percent of their bodyweight in calf starter (about 1.5 kg or 3.5 pounds) prior to weaning seemed to signify a more efficient digestive system compared to intakes of 1 percent (about 1 kg or 2.2 pounds) in terms of fermenting and digesting solid feeds.


Observing rewarded versus unrewarded feeder visits can help to identify calves struggling with weaning and the weaning program adjusted for them to avoid losses in ADG during weaning and potentially deter cross-suckling. PD

Amanda Kerr is a nutritionist with Grober Nutrition.

emily de benetti

Emily DeBenetti
Project Manager
Grober Nutrition