Nutritional Value and In Vitro Fermentation of Two Oat (Avena sativa L.) Varieties in Six Phenological Stages

Abstract

In northeastern Mexico, forage shortages during the cold season limit the availability of high-quality forage for ruminant production systems, as the growth of warm-season C4 forages declines significantly. Forage oats are widely grown to address this seasonal shortage; however, information on the optimal harvest stage and its effect on gas fermentation kinetics of commercially important cultivars under regional semi-arid conditions remains limited. Therefore, this study evaluated the nutritional value and in vitro fermentation parameters of two oat varieties (Chihuahua and Cuauhtémoc) at six phenological stages: tillering (Z2), stem elongation (Z3), stuffing (Z4), milky grain (Z7), doughy grain (Z8), and physiological maturity (Z9). The experiment was carried out using a completely randomized design, with a 2 × 6 factorial arrangement, where the fixed effects corresponded to the oat variety (Chihuahua and Cuauhtémoc), the phenological stage (Z2, Z3, Z4, Z7, Z8, Z9), and their interaction. Crude protein, ash, digestible dry matter, and relative forage value contents decreased (p < 0.05) with increasing phenological stage of the two oat varieties. In contrast, neutral detergent fiber, acid detergent fiber, and hemicellulose contents increased (p < 0.05) with increasing phenological stage of the two oat varieties. Gas production rate, lag phase, and in vitro dry matter digestibility at 72 h decreased (p < 0.05) with increasing phenological stage of the two oat varieties. In contrast, the fast fermentable fraction and total fermentable fraction increased (p < 0.05) with increasing phenological stage in both oat varieties. In conclusion, the nutritional value, gas production, lag phase, and in vitro dry matter digestibility of oats decreased as the phenological stage increased.