1. Animal Production Systems Group, Wageningen University, P.O. Box 338, 6700 AH Wageningen, The Netherlands
2. Department of Animal Science, University of Venda, Private Bag X 5050, Thohoyandou, 0950, Limpopo Province, South Africa
3. Department of Agricultural Economics and Agribusiness, University of Venda, Private Bag X5050, Thohoyandou, 0950, Limpopo Province, South Africa
4. Mara Research Station, Limpopo Department of Agriculture, Private Bag X 2467, Makhado, 0920, Limpopo Province, South Africa