Ombabi A, Südekum K H, Taube F
Institut für Tierernährung und Stoffwechselphysiologie, Kiel, Germany, Institut für Pflanzenbau und Pflanzenzüchtung, Christian-Albrechts-Universität, Kiel, Germany.
J Anim Physiol Anim Nutr (Berl). 2001 Dec;85(11-12):385-405. doi: 10.1046/j.1439-0396.2001.00354.x.
Dynamics of changes in digestibility and feed intake by sheep of two ryegrass species during primary growth Environmental impacts can cause short-term variations in chemical composition and feeding value of grass swards during growth and maturation and induce concomitant changes of intake of these grasses by animals. Continuous digestion trials are effective in observing the dynamics of these variations. Therefore this study was conducted to evaluate the effects of maturity-related alterations in the chemical composition of two ryegrass swards during primary growth on nutrient digestibilities and feed intake by sheep. Pure swards of perennial ryegrass (Lolium perenne L., variety Gremie) and Italian ryegrass (Lolium multiflorum Lam., variety Lema) were harvested daily during primary spring growth between 23 April and 19 June 1991 and each grass was offered to a group of five sheep for ad libitum intake. A continuous digestion trial design was employed to measure daily intakes and faecal outputs of organic matter (OM) and OM constituents. Digestibility values were calculated with the assumption that faecal output of day 2 represented the undigested nutrients of the grass eaten at day 0. Based on results of a preliminary study, daily intakes and digestibilities were expressed as rolling 3-day averages. The chemical composition of the grasses varied considerably with growth. Crude protein concentrations declined from 18.3 to 5.9% of dry matter (DM) for perennial ryegrass and from 17.0 to 5.4% of DM for Italian ryegrass, whereas concentrations of some cell-wall fractions markedly increased and partly more than doubled. Fibre content was slightly greater for perennial ryegrass than for Italian ryegrass over the whole growth period. The decline of feeding value with maturity was closely related to increasing concentrations of fibre components and their declining digestibility. Intake by sheep of Italian ryegrass was higher by 3 g/kg of body weight at the beginning and at the end of the primary growth period. Digestibility of the OM was greater than 80% at the start of the experiment and still around 70% after 2 months of grass growth. The decline in DM and metabolizable energy intake was much more pronounced than the decrease of OM digestibility. This could be attributed in part to a decline in feed intake capacity of non-lactating sheep caused by increasing body fat mass. Short-term fluctuations in OM digestibilities were related to alterations of chemical composition of the grasses caused by growth and maturation, in particular variations in water-soluble carbohydrate concentrations. The two ryegrass species differed with regard to nitrogen associated with the cell-wall (NDF) and lignocellulose (ADF). Continuous digestion trials were effective in observing the dynamics of alterations in feeding value and feed intake by sheep as related to growth and maturation of two ryegrass species during primary spring growth.
两种黑麦草在初生期生长过程中绵羊消化率和采食量的变化动态 环境影响可导致草地在生长和成熟过程中化学成分和饲用价值出现短期变化，并引起动物对这些牧草采食量的相应改变。连续消化试验对于观察这些变化的动态很有效。因此，本研究旨在评估两种黑麦草草地在初生期生长过程中与成熟度相关的化学成分变化对绵羊养分消化率和采食量的影响。在1991年4月23日至6月19日春季初生期生长期间，每天收割多年生黑麦草（Lolium perenne L.，品种Gremie）和意大利黑麦草（Lolium multiflorum Lam.，品种Lema）的纯草地，每种草分别提供给一组5只绵羊自由采食。采用连续消化试验设计来测量有机物质（OM）和OM成分的每日摄入量和粪便排出量。消化率值的计算假设第2天的粪便排出量代表第0天采食牧草中未消化的养分。根据一项初步研究的结果，每日摄入量和消化率以滚动3天平均值表示。随着生长，牧草的化学成分变化很大。多年生黑麦草的粗蛋白浓度从干物质（DM）的18.3%降至5.9%，意大利黑麦草从DM的17.0%降至5.4%，而一些细胞壁组分的浓度显著增加，部分增加了一倍多。在整个生长期间，多年生黑麦草的纤维含量略高于意大利黑麦草。随着成熟度增加，饲用价值下降与纤维成分浓度增加及其消化率下降密切相关。在初生期生长开始和结束时，绵羊对意大利黑麦草的采食量高出3 g/kg体重。试验开始时OM的消化率大于80%，在牧草生长2个月后仍约为70%。干物质和代谢能摄入量的下降比OM消化率的下降更为明显。这部分可归因于非泌乳绵羊体脂增加导致采食量能力下降。OM消化率的短期波动与生长和成熟引起的牧草化学成分变化有关，特别是水溶性碳水化合物浓度的变化。两种黑麦草在与细胞壁相关的氮（NDF）和木质纤维素（ADF）方面存在差异。连续消化试验对于观察与两种黑麦草在春季初生期生长和成熟相关的绵羊饲用价值和采食量变化动态很有效。
