品种及成熟期对玉米秸秆不同形态部位干物质及粗蛋白降解特性的影响

In vivo degradation characteristics of dry matter and crude protein of four morphological fractions for five varieties maize harvested at two maturity stages

玉米秸秆是反刍家畜主要粗饲料来源之一,其营养降解特性不仅受玉米品种及成熟时期的影响,而且与玉米秸秆形态部位组成相关。本试验通过分析不同类型玉米品种秸秆不同形态部位在2个成熟期干物质(DM)及粗蛋白(CP)的瘤胃降解特性,为玉米秸秆在反刍家畜中的利用提供数据支持。试验选用科湘玉11号(常规玉米)、高油115(高油玉米)、科湘糯玉1号(糯玉米)、沪青1号(饲用玉米)和科湘甜玉1号(甜玉米)5个品种玉米,分别在抽穗后的第17天(乳熟期)和第31天(蜡熟期)采集其叶片、叶鞘、茎秆及苞叶4个形态部位的样品,利用瘤胃尼龙袋技术分析所有样品的DM及CP的瘤胃降解动力学参数变化规律,结果表明:蜡熟期叶片、叶鞘、茎秆部位DM,以及叶片和苞叶部位CP的快速降解部分(a值)显著(P<0.001)高于乳熟期,但其叶片、叶鞘和茎秆部位DM,叶片、叶鞘和苞叶部位粗蛋白的慢速降解部分(b值),以及苞叶干物质有效降解率(ED)极显著(P<0.001)低于乳熟期。新培育品种玉米不同形态部位干物质及粗蛋白的a、b及ED值与普通品种玉米相近或更高。不同形态部位间DM及CP降解动力学参数也存在显著差异,ED值都按茎秆>苞叶>叶鞘>叶片的顺序依次降低。结论表明:延长成熟期主要影响秸秆DM和CP的a与b值;不同品种间DM及CP的有效降解率以高油玉米和糯玉米较高。

Maize stalk is an important source of roughage for ruminants,and its nutritional degradation characteristics are affected by variety and maturity of the maize,and also related to the composition of the component morphological parts of the maize stalk. This experiment provides data support for the utilization of maize stalk in ruminant livestock by analyzing the rumen degradation characteristics of dry matter(DM) and crude protein(CP) of different morphological parts of maize stalk at two maturity stages. Five varieties of maize:Kexiangyu No. 11(conventional maize),Gaoyou 115(high oil maize),Kexiangnuoyu No. 1(waxy maize),Huqing No. 1(forage maize) and Kexiang Tianyu No. 1(sweet maize)were selected in this experiment. Samples of the four morphological parts of leaf blade,leaf sheath,stem and husk were collected on day 17 day(milk maturity stage)and day 31(wax maturity stage)after tasselling,and an in situ degradation technique was used to analyse the kinetic parameters of DM and CP rumen degradation in all samples. It was found that the rapidly degrading fraction(a values)of DM of leaf blades,leaf sheaths,and stems,and the a values of CP of leaf blades and husks at the wax maturity stage were higher(P<0. 001)than corresponding values at the milk stage,while the slowly degrading fraction(b values)of DM of leaf blades,leaf sheaths,and stems,b values of CP of leaf blades,leaf sheaths and husks,and the effective degradability(ED)values of the husk DM at the wax maturity stage were significantly lower(P<0. 001)than those of the milk stage. The a,b and ED values of the DM and CP of the different morphological parts of the new maize cultivars were similar to or higher than those of the conventional maize. Differences in DM and CP degradation kinetic parameters were also observed among different morphological components. The ED values decreased in the order of stem>husk>leaf sheath>leaf blade. In conclusion,extending the maturity period mainly affects the a and b values of DM and CP of maize stalk. Among different varieties,the ED of DM and CP was higher in high-oil and waxy maize.