In Vitro Digestibility of Fresh Leaves and Stems of Small-Grain Species and Genotypes
Comparative studies examining relative forage digestibilities of small-grain species and genotypes are lacking. Pattern and extent of digestion and microanatomical characteristics of fresh leaves and stems were evaluated in two genotypes each of rye (Secale cereale L.), soft red winter wheat (Triticum aestivum L.), oat (Avena sativa L.), and triticale (✕ Triticosecale Wittmack). Field grown plants (mid-boot) were sampled in 1987 and 1988 at Tifton, GA. In 1987, leaf and stem anatomy were compared microscopically in fresh nondigested samples. Fresh leaf and stem segments (2.5 cm) were digested 36 h in buffered rumen fluid, serially sectioned, and examined microscopically to examine the ease and extent of digestion in specific tissues. In 1988, in vitro dry matter disappearance (IVDMD) was determined in ground (1 mm) and intact stem and leaf sections (1 cm) digested for 12, 24, 36, and 48 h. No microanatomical variation was observed among genotypes of the same species. Variation was observed among species in stem signification, stem sclerenchyma cell-wall thickness and arrangement, compaction, and shape of leaf mesophyll cells. Signified stem tissue was greatest in wheat and triticale and least in oat and rye. Rye leaf mesophyll cells were the least compact with the largest intercellular spaces. Variation was observed among species in digestibility of leaf and stem bundle sheath cells. Differentiation among genotypes for leaf IVDMD was greater in sectioned samples digested 12 to 36 h than in ground samples digested 48 h. Species varied in leaf and stem IVDMD. Oat had the lowest stem digestibility but the highest leaf digestibility. Variation for forage digestibility was observed among genotypes of all species except triticale. Variation in forage digestibility was not associated with variation observed for stem signification or arrangement and compaction of leaf mesophyll cells. Adequate variability exists within rye and oat to suggest that selection for leaf IVDMD would be effective in improving small-grain forage quality.
Copyright © 1990.