An economical analysis of milk production systems was made with lactating cows on Mombaça grass pasture receiving different sources of roughage supplementation during the dry season. The supplementations were: black oat pasture, forage sugarcane with urea and sorghum silage. The economical indicators used were: net present value (NPV) and internal rates of return (IRR). For each production system studied one cash flow was used with their particularities and productive and reproductive performances index, obtained experimentally. The cash flows were built monthly, for a 12 years period and the NPV of the systems were calculated applying discount rates of 6, 8, 10 and 12% a year. At an annual discount rate of 8% all the production systems were financially viable. The invested capital showed annual IRR of 11.91% for black oat pasture, 9.43% for forage sugarcane and 8.46% for sorghum silage. The sensitivity analysis showed that the milk selling price had greatest economic impact on the profitability of the systems.
dairy cattle; internal rates of return; net present value; roughage supplementation; sensitivity analysis
