Implications of changing birth and slaughter dates of finishing sheep and beef cattle on greenhouse gas emissions
Significant variables in the calculation of greenhouse gas (GHG) emissions are estimates of birth date and slaughter date, as these alter the amount of time on-farm and hence feed used for animals destined for slaughter. Analysis of Beef + Lamb New Zealand Economic Service farm survey data calculated average birth and slaughter dates for both finishing sheep and beef cattle at a regional scale, from 1990-2019. Data were then used to calculate the potential GHG emissions related to lambs and slaughter cattle, and changes over time, and were compared to current national inventory calculations. There was no significant change in sheep
mating date over the 30-year period, with a median lambing date of 10 September. Beef cattle mating date became later over the 30-year period. These resulted in calving dates of 20 September for the 1990-2000 period, and 25 September for the 2010-2019 period.
The proportions of lambs slaughtered by February (early) or October (late), categories used by the National Inventory, have shifted from 84 and 16% respectively in 1990 to 78 and 22% recently. The ages at slaughter of 1–2-year-old heifers and steers were approximately 24 and 35 days younger in 2019 than in 1993 (528 vs 552 days of age at slaughter for heifers and 520 vs 555 days of age at slaughter for steers). The changing proportion of lambs slaughtered early and late had a small effect on total emissions. Later birth dates and earlier slaughter dates have reduced the individual emissions from 1–2-year-old cattle, but individual emissions from older
cattle and bulls have changed little over the 27-year period examined.
How to Cite
This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
This work is licensed under a Creative Commons Attribution-Non Commercial-NoDerivatives 4.0 International License. Rights granted to the New Zealand Grassland Association through this agreement are non-exclusive. You are free to publish the work(s) elsewhere and no ownership is assumed by the NZGA when storing or curating an electronic version of the work(s). The author(s) will receive no monetary return from the Association for the use of material contained in the manuscript. If I am one of several co-authors, I hereby confirm that I am authorized by my co-authors to grant this Licence as their agent on their behalf. For the avoidance of doubt, this includes the rights to supply the article in electronic and online forms and systems.