Factors influencing composition and ruminal degradability of barley straw

Chemical composition and in situ ruminal degradability characteristics for 25 and 40 genotypes of barley straw were measured for crops grown in 1994 and 1995, respectively. Straw from semi-dwarf genotypes contained more crude protein and less neutral detergent fiber NDF) than that from genotypes with medium straw length and effective ruminal degradability was 9% higher (P < 0.01). Straw from two-row genotypes contained 19% more crude protein (4.4 vs. 3.7%) and 3% less NDF (75.2 vs. 77.6%) than that from six-row genotypes and effective ruminal degradability was 6% higher (P < 0.01) when genotypes with medium-length straw only were considered. Genotypes with smooth awns had higher rates of degradation but contained less of the slowly degraded fraction than straw with rough awns when straws of medium straw length were compared (P < 0.05). Straw from hulless genotypes contained more (P = 0.006) NDF than that from covered varieties. Both ambient and soil temperature were positively related (P < 0.05) to effective ruminal degradability of straw, possibly because of associated greater leafiness when temperatures were higher and there was more light. It was concluded that it is possible to select barley genotypes that have superior straw nutritive value for ruminant animals.