A survey on the effect of management techniques and pasture composition and quality at harvesting on silage quality on dairy farms in western Victoria

Abstract

Summary. Factors associated with silage quality were investigated on 140 dairy farms in western Victoria. The management factors measured were date of lock up, date cut, length of lock up, duration of wilting, raking and tedding during wilting period, rainfall during wilting period and the type of silage made. Pasture variables measured at harvesting included percentage composition (ryegrass, legume, other grasses and weeds), dry matter of pasture, metabolisable energy, crude protein, neutral detergent fibre and water-soluble carbohydrate of the pasture, and dry matter yield of the pasture.

The average lock up time of pasture for silage was mid September, although the range was from late July to early November. The length of lock up varied from 16 to 91 days with a mean value of 49 days and pastures were on average harvested in early November. Ryegrass on average accounted for 61%, legumes and other grasses accounting for a further 15% each and weeds about 5%. The range in quality of pasture at harvesting was highlighted by the range in metabolisable energy (8.9–11.3 MJ/kg DM) and crude protein (10.2–20.4%) values. Wilting times varied from 0.5 to 15 days with the biggest range being observed in pastures used for baled silage.

All factors were regressed against final silage metabolisable energy and crude protein. Factors which had the greatest effect on final silage metabolisable energy were date of cutting, length of lock up, type of silage, the interaction between type of silage and length of lock up, length of wilting and mechanical treatment during the wilting period. Final silage crude protein was most strongly associated with date of cutting, crude protein content of the pasture and mechanical treatment during the wilting period.

Mechanical treatment during the wilting period had the greatest influence on silage quality. Other options to improve silage quality such as cutting earlier or reducing wilting periods may not be possible or economically viable.