Ruminal degradability of brown-midrib sorghum-sudangrass hybrids for cutting and grazing

ABSTRACT Greater ruminal degradability has been reported in mutant plants with brown midrib (bmr). The aim of this study was to evaluate the in situ degradability of dry matter (DM), neutral detergent fibre (NDF) and crude protein (CP) in the experimental sorghum-sudangrass bmr hybrids BR007 x Tx2784bmr and Tx635x Tx2785bmr, conventional experimental hybrids CMSxS206 x Tx2784 and Tx636 x Tx2785, and the control hybrid BRS801, harvested 51 days after planting. Three sheep with ruminal cannulae were used. The experimental design was of randomised complete blocks in subdivided lots. The mean values for DM and NDF disappearance were higher in the bmr hybrids after 6 h incubation. These plants had a higher rate of degradation (mean value of 6.93%/h) for fraction b of the DM compared to conventional plants (mean value of 5.73%/h), and greater effective DM degradability. The mean values for effective NDF degradability at passage rates of 2, 5 and 8%/h were 72.7% and 62.0%, 56.1% and 45.6%, and 47.1% and 37.3% for the bmr and conventional hybrids respectively. The experimental mutant hybrids showed higher values for effective CP degradability in relation to the remainder, however, the differences were more subtle in relation to those seen for DM and NDF. The results of the present work show the potential of using sorghum-sudangrass bmr hybrids in systems of ruminant production with high nutritional requirements.

摘要：已有研究表明，褐中脉（brown midrib, bmr）突变体植物的瘤胃降解率更高。本研究旨在评估试验用高粱-苏丹草bmr杂交品种BR007 × Tx2784bmr、Tx635 × Tx2785bmr，常规试验杂交品种CMS×S206 × Tx2784、Tx636 × Tx2785，以及对照品种BRS801在种植51天后的干物质（dry matter, DM）、中性洗涤纤维（neutral detergent fibre, NDF）与粗蛋白（crude protein, CP）原位降解特性。试验选用3只安装瘤胃瘘管的绵羊，采用裂区随机完全区组试验设计。孵育6小时后，bmr杂交品种的干物质与中性洗涤纤维消失率均值更高。相较于常规品种（均值为5.73%/h），bmr杂交品种的干物质b组分降解速率更高（均值为6.93%/h），且干物质有效降解率更优。当流通速率分别为2%/h、5%/h与8%/h时，bmr杂交品种与常规杂交品种的中性洗涤纤维有效降解率均值分别为72.7%与62.0%、56.1%与45.6%、47.1%与37.3%。试验用bmr突变体杂交品种的粗蛋白有效降解率也高于其余品种，但该差异相较于干物质与中性洗涤纤维的差异更为细微。本研究结果表明，高粱-苏丹草bmr杂交品种在高营养需求反刍动物生产体系中具备应用潜力。