Feasibility of Alternative Grass Silage Systems: Part 2, Economic Assessment

Abstract

Three novel silage making technologies described in Part 1, mat making, dewatering and absorbents, were tested in simulations over a 10-year period of grass growth, silage conservation and feeding to a dairy herd, using a whole-system forage conservation model. The novel technologies were compared with a conventional system using a mower-conditioner and a precision chop harvester. Simulation results showed that mat making improved profitability by as much as £2400 per year on a 40 ha, 100 cow farm. About £600 gain was due to reduced field losses, another £600 was attributed to improved digestibility and £1200 was due to the replacement of the forage harvester by a lower-cost mat harvester. Optimization of mat making suggested mowing only in the morning so that most mats reached 25 to 30% dry matter in the afternoon and could be ensiled on the same day the forage was mowed. The benefits of dewatering, in terms of reducing purchased supplemental feedstuffs because the juice and fibre could be fed separately, amounted to £1000 per year. However, this was too small a saving to cover the extra cost of equipment and chemicals to separate and preserve the juice. The use of absorbents was also not economic if applied in sufficient quantities to have any worthwhile effect on effluent production. Of the three technologies considered, only mat making offered the prospect of an economically acceptable means of reducing effluent production from unwilted silage.