Feasibility of Alternative Grass Silage Systems: Part 1, Description of Models

Abstract

The economic and environmental impacts of three alternative grass silage systems, namely, mat making, dewatering and absorbents are assessed. The three alternative systems are described mathematically in Part 1 of the study. Mat making is conceptually achieved with a machine that combines mowing, severe conditioning (maceration), compression into a thin mat and deposition onto the stubble. The mat maker costs about 2·5 times as much as a mower-conditioner but it reduces field losses because of a very rapid wilt and it yields a highly digestible fibre. Mechanical dewatering consists of harvesting the wet forage and separating it into two products at the storage site, namely, a wet fibre and a nutrient rich forage juice. Separate feeding of the juice and fibre would reduce the need for purchased supplements, since the proportion of juice fed can be increased in early lactation when nutrient demands are highest. Absorbents increase the dry matter content in the silo, thus reducing effluent flow and sometimes improving the feed value of wet silage. The models are described in a form suitable for simulations of the daily performance of each system over a number of years; the results of the simulations are described in Part 2 of the the study.