Age of First Calving


Within all dairy economies, the cost of production and the volume of lifetime ruminant  greenhouse gas (GHG) emissions is influenced greatly by the age of first calving. A heifer is likely to be weaned (and therefore commence eructation) at 8 weeks. This means that  an animal calving for the first time at 2 years will have been emitting GHG for 674 days before producing food for human consumption, while an animal that calves for the first time at 3 years will have been emitting GHG for 1,039 days. Whilst only 10% of the rearing cost is pre-weaning, management systems that ensure a heifer receives excellent nutrition, whether in the form of high-quality milk powder, or the nutritionally more variable whole milk, during rearing, will give the individual the best possible chance of an Age of First Calving (AFC) of 2 years, and therefore minimise the GHG emissions, see table 1. 


Age at first calving

Lifetime production (kg)

Total methane produced (kg)

22 months



23 months



24 months



25 months



26 months



27 months



Table 1. Van Laar et al. (2004), Van Straalen (2006)


Calving Intervals


Minimising the negative energy balance and associated post-partum anoestrus, by satisfying the nutritional needs of a recently calved heifer or cow, will ultimately aid in returning a cow to in-calf ideally after 50-70 days rather than the average of 100 days plus. This will ultimately ensure both the productivity and profitability of a dairy enterprise but also reduce the GHG emissions per litre of milk produced. 

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