The historical focus for breeding management in most developed dairy industries has been to maintain 12-month calving intervals (CI) so as to maximise milk yield/cow/annum and per cow/lifetime. The calvings within a herd may occur throughout much of the year (year-round calving), or be concentrated into a single period of about 12 weeks (seasonal calving). Year-round calving is most common in industries where most milk is consumed fresh and only the surplus is processed as powder, butter, cheese or casein. Seasonal calving is typical of industries that process most milk into dairy products that are consumed locally or exported.
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