1. Department of Agribusiness and Agricultural Economics, University of Manitoba, Winnipeg, MB R3T 2N2, Canada.
2. Agriculture and Agri-Food Canada, Brandon Research and Development Centre, Brandon, MB R7A 5Y3, Canada.
3. Box 83, Rivers, MB R0K 1X0, Canada.
4. Agriculture and Agri-Food Canada, Lacombe Research and Development Centre, Lacombe, AB T4L 1W1, Canada.
5. Saskatchewan Ministry of Agriculture, Prince Albert, SK S6V 6G1, Canada.