Keywords: filling data gaps | milk yield | extrapolation | dairy cattle
Country context: Canada is a large and diverse country. Production practices vary across the country
with differences in land prices, climate, forage availability and market access. Canada’s inventory adopts a Tier 2 approach, but the inventory uses static values for the basic parameters describing dairy cattle production. For example, live weight, pregnancy rates and so on have the same value in each year. However, milk yield changes markedly over time.
What data needs were addressed? To develop a national time series for average milk yield per animal.
Why was the data needed? Milk productivity has increased in all Canadian provinces over time. CanWest DHI a producer-owned milk recording organization collects a sample of milk production representing more than two-thirds of the Canadian dairy cow population for the period of 1999–2015. These data give the best estimate of actual milk production per cow per province in Canada. However, from 1990 to 1998, this data set does not exist for the whole country. The only data that are available from 1990 to 1998 for all of Canada are data reported by Agriculture and Agri-Food Canada, which are collected on the most productive animals and during the first 305 days of lactation only.
Methods used: extrapolation.
How was the data gap addressed? The time series of real milk production for the entire Canadian herd from 1990 to 1998 was calculated based on the average ratio between the data published by Agriculture and Agri-Food Canada and the milk recording data from 1999 to 2007. The trend of increased milk production is then reflected in the emission factor for dairy cows.