The concept of extended lactation is a break with the tradition of getting one calf per cow per year that should improve cow health, increase productivity and reduce greenhouse gas (GHG) emission per kg milk produced in high-yield organic dairy herds. These effects are achieved through fewer calvings per year and hence a production of fewer replacement heifers, which, in combination with fewer days dry per cow per year, will reduce the annual herd requirement for feed. Total herd feed use is a major determinant of GHG emission at farm gate. However, these effects also rely on the assumption of an unchanged milk production per feeding day (days lactating plus days dry) when changing from lactations of traditional length to extended lactations. Thus, milk yield per feeding day becomes a primary determinant of the success of using extended lactations at farm level. Cows undergoing an extended lactation will be able to produce milk for the same number of lactations and thus have longer, more productive lives. Additionally, cow health may be improved as the majority of diseases occur around calving. Increased productivity and improved cow health should also improve farm profitability, although fewer bull calves and fewer culled cows will be available for sale. An on-going project at Aarhus University aims at characterising those cows that can maintain milk production through an extended lactation, and it aims at estimating the overall herd effect of this concept on farm profitability and GHG emission per kg of milk produced.
Organic Agriculture, 2014, Vol 4, Issue 4, p. 295-299