[目的]研究不同品种玉米生长后期植株剪切力和饲料营养特性的变化规律以及相互关系.[方法]选择3个玉米品种,从播种后第78天开始,每隔5d,分7个时期(每期每个品种选24株)测定植株主要营养器官(茎秆、叶片、叶鞘)的剪切力、线性密度、营养成分含量;分乳熟期、蜡熟期和完熟期测定三大营养器官营养成分的48 h瘤胃降解率.[结果]随着玉米的生长,茎秆剪切力和线性密度线性增加,品种间差异显著(P＜0.05);叶鞘剪切力线性增加(P＜0.05),叶鞘和叶片线性密度线性降低(P＜0.01),品种间无差异(P＞ 0.05).叶鞘、茎秆的剪切力与线性密度相关显著(P＜0.05).在鲜样基础上,茎秆、叶鞘中的干物质(DM)、有机物(OM)、中性洗涤纤维(NDF)、酸性洗涤纤维( ADF)含量和总能(GE)线性增加,茎秆中粗蛋白(CP)含量呈线性降低,不同品种间有差异(P＜0.05);叶片中DM、OM、NDF和ADF含量逐渐增大(P＜ 0.05),品种间无差异(P＜0.05);叶鞘、茎秆的剪切力与营养成分相关显著(P＜0.05).所测定营养物质的48h瘤胃降解率,不同器官之间差异显著,结果为叶片＞叶鞘＞茎秆(P＜ 0.05).叶鞘的剪切力与营养成分降解率相关显著(P＜0.05).[结论]玉米生长后期(播种后78-108 d)剪切力、营养成分和养分降解率呈动态变化;植株剪切力与其饲料特性存在相关关系,选用剪切力预测植株营养成分含量和利用率,需根据植株的不同器官和具体品种应用.%[Objective] The objectives of this study were to investigate the changing laws and the relationships between shearing force and nutritional ingredient of growing maize plant, and further prove confirmation that shearing force is one way of evaluating nutritional ingredient of forage. [Method] The shearing force, linear density and chemical compositions of leaf, pericladium and stem of three varieties of maize, each of 24 plants, were measured at 5-day intervals during the 78-108th d. Meanwhile, three sheep fitted with permanent cannulas in rumen were used to determine in situ degradability in 48 h of the nutrients of three chief vegetable organs at the milk stage, dough stage and physiological maturity stage. [Result] The results showed that linear density and shearing force of stem linear increased with maize growth and there was a difference among varieties (P<0.05). Shearing force of pericladium linear increased (P<0.05), and the linear density of leaf and pericladium linear reduced (P<0.01). There was a significant correlation between shearing force with linear density of pericladium and stem (P<0.05). The contents of DM, OM, NDF, ADF and GE in pericladium and stem on the base of fresh matter linear increased, contents of CP linear reduced, there was a difference among varieties (P<0.05), and the contents of DM, OM, NDF and ADF in leaf had a linear increase (P< 0.05), during the 78-108th d. Of maize growth. A significant correlation was found between shearing force and chemical compositions of pericladium and stem (P<0.05). In situ degradability of leaf decreased with increasing shearing force, and there was a difference among the three chief vegetable organs (P<0.05). [Conclusion] The shearing force, chemical compositions and in situ degradability of maize plant showed a dynamic change during the 78-108th d. Stage. Shearing force can be employed to predict the chemical composition and utilization of growing maize plant, but different organs and varieties should be taken into consideration.
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