Invited Review: The weaning transition in dairy calves—Why so traumatic?*

Purpose

The purpose of this review article was to identify physiological and management factors that affect the weaning transition in dairy calves, which can be a dif- ficult time for calves.

Sources

Peer-reviewed journal articles were used to compile the review.

Synthesis

Weaning is often a period of stress and lost performance for calves, in many cases resulting in respira- tory disease or diarrhea caused by coccidiosis or acidosis. Physiological factors contribute to the difficulty, including the expanding gut fill, allometric growth of the reticuloru- men and gastrointestinal tract, and development of the ruminal epithelium. Stabilizing ruminal pH above 6.0 so that fiber fermentation can proceed is a major challenge for calves. Management practices should aim to maximize starter intake while avoiding ruminal acidosis. Providing a high-quality calf starter is extremely important, including appropriate ingredient and chemical composition as well as physical form. Calves should not be weaned until they are consuming an adequate amount of starter to allow the discontinuation of milk intake and should be weaned gradually rather than abruptly. Although small amounts of forage before and after weaning may be useful in calves fed pelleted or ground starters and not bedded on straw, calves should not have free access to alfalfa hay. Water ac- cess is critical because the rumen needs water to support the developing microbial ecosystem. Stressful management tasks such as dehorning or vaccination should not be per- formed at the same time as weaning. Ruminal acidosis is likely more common than has been recognized and causes decreased intake, decreased growth, and diarrhea, espe- cially in calves soon after weaning.

Conclusions and Applications

The weaning tran- sition is a period of stress for calves. Managing starter quality, time and rate of weaning, forage and water avail- ability, concurrent stressors, and acidosis can help avoid difficult weaning and improve the welfare of young calves without losing performance.