Morphological fractions, chemical composition and in vitro digestibility of stover of four common vetch varieties grown on the Tibetan plateau.

Abstract

This study evaluated the varietal variability and interrelationship of the grain and stover yields, and stover quality characteristics of four common vetch varieties (three improved varieties and one local variety) used on the Tibetan Plateau. Stover quality attributes determined included chemical composition, in vitro true digestibility of dry matter (IVTD) and neutral detergent fibre (dNDF). The improved varieties were superior to the local variety in grain yield, harvest index and potential utility index (PUI). The wide ranges in the proportions of leaf (24.3%-34.6%), pod (22.0%-45.6%) and stem (29.5%-44.7%) fractions were observed. Significant varietal differences (p<.001) were observed for the whole-stover content of crude protein [CP; 78.1-101g/kg dry matter (DM)], neutral detergent fibre (aNDF; 520-564g/kg DM), acid detergent fibre (ADF; 520-564g/kg DM), IVTD (597-658g/kg DM) and dNDF (305-384g/kg aNDF). The leaf fraction had the highest levels of CP, IVTD and dNDF, while the highest contents of aNDF and ADF were observed in the stem fraction. Canonical correlation analysis showed that significant (p<.001) correlations between the quality attributes of whole stover and proportions and quality attributes of stover morphological fractions. Pearson correlation between the grain and stover yield was negative and significant (r=-.295; p=.001), while the correlations between the grain/stover yield and stover quality traits were positive or non-significant. Ranking of the varieties differed when grain yield, PUI and stover quality scores were investigated. Of the varieties tested, Lanjian No.2 has the best potential for use as a ruminant feed, as indicated by PUI and stover quality.