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Extended lactations to reduce greenhouse gas emissions from dairy cows - AC0223

The UK Government is committed to reducing greenhouse gas emmissions (GHGE), to by 80% of 1990 levels, by 2050. The ruminant livestock sector of agriculture, of which the dairy industry is a significant part, is particularly responsible for producing a large proportion of the UK's nitrous oxide and methane emmisions. Any method to help reduce GHGE at the farm level could have a large impact on the national GHGE targets. Several other Defra projects are looking at a range of methods to achieve this in the dairy sector. This project is taking an idea that has been talked about for about 20 years, using extended lactations in milk production, and investigating whether its introduction into the dairy sector might have benefits in reducing GHGE. Extended lactations are those designed to be longer than the 'normal' lactation length required to fit into an annual calving pattern, traditionally deemed to be the desired system of dairy production in the UK. It has been postulated that extended lactations could have benefits to the individual dairy herd by reducing risk associated with calving, improving fertility, improving health, increasing longevity and reducing the number of replacements required. If this were found to be so then there could be important consequences at the national level of a reduction in the number of cows and followers in the national dairy herd. In addition, it is expected that extended lactations could lead to more efficient milk production. If both these effects were found to occur in practice and farmers increased their use of extended lactations then there should be a reduction in GHGE from the national diary herd. This project is designed to test these ideas in a desktop modelling study at both the individual herd and national level.

The proposed approach is firstly to collect together all information relating to the use of extended lactations in the dairy sector. This will come from published papers and reports as well as from analyses of UK-based data available to the project team. Once the current state of knowledge has been assessed this will be used in two computer models to see how the use of extended lactations could affect both farm level and national level production factors. These models will incorporate GHGE information and the results will reflect how GHGE emmissions are expected to change under a range of extended lactation scenarios. Where there are current knowledge gaps these will be highlighted and, if they are crucial to running the models, they will be included as variables to be investigated in the computer simulations. The ideas developed in these analyses will be discussed with industry representatives to gague their likely uptake and collect industry reactions to the ideas. The final report and results will be widely distributed and disccussed with the key stakeholders.
7. (b) Objectives

The overall aim of the project is to investigate the potential for reducing UK greenhouse gas emissions (GHGE) using extended lactations in the dairy industry. Extended lactations are those which are longer than required to achieve an annual calving interval (a one-year period between successive calvings). This work is intended to follow up the unsupported suggestion by Hopkins and Lobley (2009) that the adoption of such a system could lead to reduced GHGE.

1. Review experiments, industry data analyses and economic modelling in UK and elsewhere into extended lactations and determine the technical (yield, milk composition, reproduction, health, welfare) and economic feasibility of extending lactation length per cow from 305 days to 450 days (15 months) so that cows calve at 18-month intervals rather than at 12-month intervals (i.e. two lactations in three years v three lactations in three years).

2. Determine the relationships between peak yield, total lactation yield, persistency and calving index in the UK dairy herd.

3. Establish the extent to which extended lactations occur by default in UK dairy herds, and reasons for its occurrence.

4. Determine whether or not the current output of milk in the UK could be sustained through the adoption of extended lactations in the national dairy herd, and if so what size of milking cow and herd replacement population would result, if the current levels of dairy cow fertility and longevity are maintained.

5. Determine the potential impact on greenhouse gas emissions from the dairy sector of the adoption by dairy farmers of extended lactations.

6. Examine research and industry data into extended lactations to identify any negative impacts that they might have on other aspects of milk production e.g. seasonality payments, lower milk price due to higher somatic cell counts.

NB The objectives in the original project specification have been rearranged above to make a more natural flow to the work.

Project Documents
• Final Report : Extended lactations to reduce greenhouse gas emissions from dairy cows   (2009k)
• Final Report : Extended lactations to reduce greenhouse gas emissions from dairy cows   (816k)
• Summary Report : Extended lactations to reduce greenhouse gas emissions from dairy cows   (38k)
Time-Scale and Cost
From: 2009

To: 2010

Cost: £68,481
Contractor / Funded Organisations
Royal Veterinary College
Agriculture and Climate Change              
Greenhouse Effect              
Sustainable Farming and Food Science              
Fields of Study
Agriculture and Climate Change