Estimated metabolizable energy yields of perennial and annual grass swards compared with those of spring barley and oat

The dry matter yields of cultivar trials (from 1976 to 1998 at 15 sites in Finland) of perennial grass sward (meadow fescue (Festuca pratensis) cv. Boris), annual grass sward (Italian ryegrass (Lolium multiflorum), cv. Barmultra and Mitos), spring barley (Hordeum vulgare cv. Otra, Arra, Arve) and oat (Avena sativa cv. Veli) were used to estimate metabolisable energy yields (MEY) by using the feeds metabolisable energy concentration values (MJ/kg DM) from ruminant feed tables. Harvest index (HI) of barley and oat was set to 50%, and straw yields and whole crop cereal silage (WCCS) yields were generated from grain yields accordingly. The MEY in the third year of perennial grass (81.4 GJ/ha) was significantly lower than that in the first (90.0 GJ/ha) and second years (90.7 GJ/ha). However, on average, the one to three year old perennial grass-swards had significantly higher MEY than the annual grass swards (87.7 vs. 83.3 GJ/ha, respectively). The MEYs of perennial and annual grass swards were substantially higher than the MEY of barley grain (52.7 GJ/ha) and oat grain (47. 8 GJ/ha). When the total herbage of cereals, i.e. straw and grain, was used in the calculations, at a ME value of 6.0 MJ/ kg dry matter (DM) for straw, the MEY of barley rose to 75.8 GJ/ha and that of oat to 72.6 GJ/ha. Additionally, the MEY of barley was estimated in the WCCS production situation by converting total herbage to MEY by using ME value 9.9 MJ/kg DM. The MEY of barley in the WCCS calculations was 77.4 GJ/ha, which was significantly lower than the MEY of annual and perennial grass swards. The MEY of barley was a) 60%, b) 86%, and c) 88% of the average MEY of one to three year old perennial grass sward when the MEY of barley was calculated according to a) grain, b) grain + straw, and c) whole crop cereal silage. Perennial grass sward was the most productive of the studied crops in metabolisable energy production for ruminants.