How the ingredients of a ruminant’s diet can help save the world - Part 4
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.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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.