Variation in Hull Composition and Digestibility Among Oat Genotypes1

Abstract

Little attention has been given to the study of genotypic variation in the composition and digestibility of oat (Avena sativa L.) hulls. The aim of this study was to examine the variability in levels of acid detergent fiber (ADF), its components—cellulose, acid detergent lignin (ADL), and insoluble ash (mainly silica)— and pepsin cellulase digestibility (PCD) in hulls separated from current Western Australian genotypes. Analyses were conducted on six genotypes grown in trials at up to seven locations in Western Australia in 1981. In 1983, the same genotypes, and one other, were tested at five locations. In both years, considerable genotypic variance was observed in levels of PCD, ADF, and ADL. Location affected all traits, particularly insoluble ash, in both years. Genotype ✕ location interaction was not measured in 1981, but in 1983 was found to be significant for all traits. Interaction effects were of sufficient magnitude to mask the small genotypic variations in cellulose, but clear differentiation between genotypes with high or low PCD, ADF, and ADL was observed at each location. While PCD was highly correlated with ADF (r = −0.97** (significant at the 0.01 probability level), based on means for each of seven genotypes over five locations), differences between genotypes in both PCD and ADF were associated mainly with ADL (r = −0.98** and 0.95**, respectively). Among the genotypes tested, Swan (PCD, 293 g kg−1 ; ADL, 8 g kg−1) and ‘Mortlock’ (PCD, 108 g kg−1; ADL, 76 g kg−1) had the highest and lowest quality hulls, respectively. This study has shown considerable variation to exist in the highly correlated factors PCD and ADL among current Western Australian genotypes, and indicates potential for improvement in the feeding quality of oat grain through plant breeding.