The effect of cultivar on the rate and extent of combining pea straw degradability examined in vitro using the Reading Pressure Technique

Although about 225 000 t dry matter (DM) pea straw is produced annually in the UK, no recent data exist with respect to its nutritive value when offered to ruminants. This study, to examine field pea crop waste (straw) from 12 commercial cultivars of combining peas, was therefore undertaken when material grown as part of a European field pea network trial at Reading in 1998 was made available. The straw was subjected to chemical analysis and examined in vitro using the Reading Pressure Technique to generate gas production profiles and to determine both rate and extent of DM and organic matter degradation. Ash and crude protein (CP) concentrations (69 and 65 g kg^–1 DM) were generally lower than published values for legume straws but higher, especially CP, than cereal straws. Neutral‐detergent fibre concentrations were slightly lower, and metabolizable energy (ME) values, derived from degradable organic matter assessed in vitro (iOMD), higher than cereal straws, ranging from 6·0 to 8·1 MJ ME kg^–1 DM. Both cumulative gas production and rate of gas release varied significantly between cultivars, as did degradation with 96‐h iOMD values ranging from 468 to 602 g kg^–1. By combining these with the quantity of material harvested, ME yields for the different cultivars were found to range from 15 to 27 GJ ME ha^–1. Considerable, and general highly significant, variation was found between the cultivars examined, which may be used to rank straws with respect to their nutritive value. The cultivars Baccara and Solara followed by Athos and Vital were readily ranked higher than the other cultivars in terms of in vitro fermentation parameters and ME yields. These data suggest that pea straw, although often incorporated into the soil in post‐harvest operations, shows excellent potential as a ruminant forage feedstuff.