Abstract & Overview
The thesis summarises and discusses six studies, presented as three papers, concerning harvest and treatment of pea-based silages for use in dairy production. The studies were performed at the Swedish University of Agricultural Sciences Research Farm at Röbäcksdalen, Umeå, Sweden (63'35´N, 20'45´ E) in 2000 – 2004, using Swedish Red cows housed in a tie-stall barn. Maturity stages and silage treatments (acid addition or wilting) were compared for effects. A laboratory silo experiment with whole-crop pea silages revealed that proteolysis was reduced at later maturity stages, and that both wilting and acid addition reduced proteolysis during ensilage. In the other studies, pea-oat bi-crop silages (seed rate 80:20) were produced. In the first study (18 cows), treatment did not change the intake of silage cut when peas were at the flat pods stage, and acid-treatment was preferable for harvesting at desired maturity stages. In the second study (30 cows), including a 7-day in vitro apparent digestibility study (15 cows), wilting to ≥ 250 g kg-1 dry matter, then adding 6 l acid tonne-1 fresh matter, resulted in good quality silages. Silages harvested when peas were at the pod fill, and oats at the early dough stage gave the overall best intake, digestibility and milk production. Finally, a production experiment (48 cows), including a 7-day in vitro apparent digestibility experiment (18 cows), showed that optimally harvested pea-oat bi-crop silage can replace, and improve, the effect of high-quality grass-clover silage on silage intake, diet digestibility and milk production. Thus, it is recommended to harvest pea-oat bi-crop silage (seed rate 80:20) when the peas are at the pod fill stage, wilt it to ≥ 250 g kg-1 dry matter and then add 6 l acid tonne-1 fresh matter. This silage can replace high-quality grass-clover silage (11.3 MJ metabolisable energy) in diets to high-yielding dairy cows, and mixed pea-oat and grass-clover silage (0.50:0.50) has a concentrate-sparing effect.