RESUMEN
BACKGROUND: The effects of growth stage (GS) and ensiling were assessed on whole-crop oat's (Avena sativa L. cv. Cantara) chemical composition, silage fermentation quality and in situ ruminal degradability. Oat was harvested and ensiled at six GS: boot, heading, water ripe, early milk, early dough and grain ripe (144, 151, 178, 234, 362 and 512 g kg-1 of dry matter (DM) of whole-crop forage, respectively). RESULTS: GS influenced chemical composition, silage fermentation quality and ruminal degradability of whole-crop oat. Lower DM and higher water-soluble carbohydrates (WSC) contents lead to adequate forage compaction and fermentation at early GS; however, effluent was produced until the dough stage (L and Q; P ≤ 0.003). Advancing in maturity increased (P < 0.001) crop yield (4.5 to 9.4 t DM ha-1 ), DM (144 to 512 g kg-1 ), neutral detergent fibre (NDF; 537 to 571 g kg-1 DM), lignin (44.6 to 71.3 g kg-1 DM) and starch contents (26.4 to 201 g kg-1 DM), and reduced (P < 0.001) crude protein (107 to 60 g kg-1 DM) and WSC (115 to 17.5 g kg-1 DM). DM and NDF ruminal degradability declined with maturity for fresh and ensiled forages (L and Q; P < 0.05). Density and buffering capacity decreased with GS (L and Q; P < 0.001), whereas pH and soluble protein increased (L and Q; P ≤ 0.004). CONCLUSION: The growth stage of oat influenced the nutritive value and ruminal degradation to a greater extent than ensiling, and thus it can play a paramount role in whole-crop oat silage quality. © 2021 Society of Chemical Industry.