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PICO question

In dairy cattle, which months should producers target age at first calving in order to maximise milk yield, minimize risk of non-voluntary culling and optimize fertility?


Clinical bottom line

Category of research question


The number and type of study designs reviewed

Seventeen papers were critically reviewed: 15 sets of case series, one review of case series and cohort studies and one randomised control trial, summarising over 2.4 million individual cow records

Strength of evidence


Outcomes reported

An optimum range of age at first calving (AFC) on dairy farms appears to be 22–25 months inclusive. Lower or higher than this figure can bring lower first lactation 305 day and lifetime milk yields, lower fertility and lower chances of surviving to a second lactation. Achieving an AFC of 22–25 months can bring the highest economic return to dairies


Age at first calving is a useful and key performance parameter to measure in dairy cattle. Achieving a range of 22–25 months at first calving can help to optimise both long term milk yield, fertility and longevity within the herd


How to apply this evidence in practice

The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.

Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.


Open Access Peer Reviewed