Impact of grazing intensity on herbage intake, composition, and digestibility and on live weight gain of sheep on the Inner Mongolian steppe

High grazing pressure during the last decades caused severe ecological problems in the steppe of Inner Mongolia, China. The objective of the present study was to determine the effects of grazing intensity of sheep on herbage mass (HM) and intake, chemical composition and digestibility of herbage, and on live weight gain (LWG). A grazing experiment with six different grazing intensities (1.5, 3.0, 4.5, 6.0, 7.5, and 9.0 sheep/ha) was conducted in the growing season of 2005 in the Xilin River Basin. HM decreased from 1.5 t DM/ha at the lowest grazing intensity to 0.6 t DM/ha at the highest grazing intensity. NDF content of the herbage was high (> 700 g/kg DM) and relatively constant, whereas acid detergent lignin (ADL) content increased with grazing intensity and with proceeding grazing season. Digestibility of organic matter ingested (DOM) tended to decrease with grazing intensity as well as intake of organic matter (OMI) and of digestible organic matter (DOMI) per sheep (P = 0.090 and P = 0.065, respectively), whereas LWG per sheep decreased with increasing grazing intensity (P = 0.018). DOM and OMI were negatively related to ADL content. However, herbage intake and LWG per ha increased with grazing intensity (P < 0.001) and reached their maximum at 9 and 7.5 sheep per ha, respectively. This observation confirms the current farmers' practise of high grazing pressure ignoring long term grassland productivity and ecological problems. Therefore, the studies are continued to provide further information on long term effects. This study could show pronounced effects of grazing intensity on animal and grassland productivity and the suitability of the methods applied to measure intake and digestibility of herbage in a large scale grazing experiment with sheep.     

链烷技术估测典型草原不同放牧率绵羊食性食量方法研究

为了进一步探讨饱和链烷技术在典型草原自由放牧家畜中的应用,定量研究自由放牧绵羊食性及食量,于2004年6-9月在中国科学院内蒙古草原生态系统定位研究站放牧样地进行试验,选择体重及体况相近、健康无病的二岁羯羊(内蒙古细毛羊×蒙古羊)60只,按体重(36.9±2.6) kg聚类分组,设置6种放牧率(0,1.33,2.67,4.00,5.33和6.67羊/hm²)的轮牧实验,绵羊采食量的测定选择放牧率为1.33,4.00和6.67羊/hm²的处理,试验开始,每只羊投喂1粒QSM饱和链烷缓释胶囊。食性测定选用全部的放牧率进行,同时辅助全粪法、扣笼法一同评价。试验期内定期收集试验地牧草样品及绵羊粪便样品,使用气相色谱分析牧草和粪样中的链烷含量,应用链烷技术估测放牧绵羊的排粪量、牧草采食比例和干物质采食量。结果表明,植物链烷模式存在种间差异,运用链烷技术估测的排粪量和实际测得排粪量差异不显著(P>0.05),放牧绵羊主要采食7~9种牧草,且不同放牧季节不同放牧率绵羊采食的牧草种类和比例不同,但采食量差异不显著(P>0.05)。本研究表明,运用链烷技术结合扣笼方法可以估测天然草地自由放牧家畜牧草的采食比例、干物质采食量和排粪量。     

内蒙古不同草原类型土壤呼吸对放牧强度及水热因子的响应

土壤呼吸的测定对于预测不同生态系统碳收支起着关键性作用。本研究利用Li-8100开路式碳通量测定系统,对内蒙古荒漠草原、典型草原和草甸草原生态系统在不同放牧强度(零放牧的对照、轻度放牧、中度放牧和重度放牧)下土壤呼吸速率进行测定,并分析了土壤呼吸与土壤温度(10 cm处)和空气相对湿度的相关性。结果表明,草地类型、放牧强度及它们的交互作用都对土壤呼吸有显著影响(P<0.05),放牧强度对土壤呼吸的影响主要表现在荒漠草原和典型草原生态系统,对草甸草原没有显著影响。在不同草地生态系统中,随着放牧强度的增加,土壤呼吸速率呈先升高后降低的变化规律。方差结果显示,不同草原类型的土壤10 cm温度和空气相对湿度有极显著性的差异(P<0.001),不同放牧强度对土壤10 cm温度和空气相对湿度无显著性影响。     

放牧强度对克氏针茅草原植物功能群的影响

植物功能群及其多样性是维持群落结构复杂性和稳定性的基础,一定程度上反映着草地生态系统的健康状况。本研究以内蒙古呼伦贝尔草原的克鲁伦河流域草原为研究对象,以植物生活型划分功能群类型,比较了3种放牧强度对植物功能群的组成结构、地上生物量和优势度的影响。结果表明,1)轻牧、中牧和重牧3种放牧条件下的总物种数分别为20、23和18种,符合"中度干扰假说";3种放牧强度下多年生非禾草物种数在群落中均占较高比例。2)轻度放牧条件下物种丰富度较低,但各放牧强度下功能群多样性无显著差异(P0.05),物种丰富度与功能群多样性无显著关系。3)随着放牧强度的增加,多年生禾草和灌木、半灌木在群落中的优势地位呈现下降趋势,与之相反,多年生非禾草优势地位越来越显著。重度放牧增加了一、二年生草本在群落中的物种数和地上生物量,但与轻牧、中牧相比,其优势度无显著变化(P0.05)。     

放牧率对绵羊体重及繁殖性能的影响

通过不同放牧率对内蒙古本地绵羊(母羊)连续2年(2008～2009)的体重和繁殖性能的影响的研究表明:(1)在试验期内,随着时间的推移,不同放牧率下的绵羊体重总体上都呈上升趋势;间隔1个放牧率或以上的处理间,存在不同程度的显著性差异;(2)绵羊的个体增重与放牧率之间存在负相关关系;而公顷增重与放牧率的关系符合二次曲线关系,在达到公顷最大增重前,随着放牧率的增大而增大,之后随着放牧率的增大减小;(3)单位家畜增重和单位面积增重的交点的生态学意义在于放牧率为1羊/hm2,公顷增重和家畜个体增重相同;单位家畜个体增重对应的畜产品最优放牧率为0.50羊/hm2,单位面积家畜最大增重对应的畜产品最优放牧率为2.38羊/hm2;(4)过高的放牧率导致绵羊出现空怀现象及产羔率下降;羔羊的初生重和个体增重均随着放牧率的增大而减小,但其显著性差异仅表现在较高的放牧率与较低的放牧率之间,而在相邻放牧率间差异不显著。     

内蒙古牧区放牧羊的福利养殖现状分析

内蒙古牧区放牧羊来自天然大草原, 以其肉质鲜美、多汁、无膻味、绿色无污染而享誉国内外。面对发达国家日益加剧的“动物福利”贸易壁垒, 打造内蒙古福利肉羊品牌, 打破世界贸易壁垒, 提高内蒙古肉羊产业的国际竞争力已迫在眉睫。对内蒙古牧区放牧羊的福利养殖现状进行分析评估, 以期为加速推进内蒙古牧区放牧羊福利养殖提供参考。     

Effect of grazing frequency and intensity on Lolium perenne L. pastures under subtropical conditions: Herbage quality

Abstract

The cellulase dry matter disappearance (CDMD) and herbage nitrogen (N) of Lolium perenne (perennial ryegrass) were evaluated for pastures grown under subtropical conditions for two years, under five combinations of grazing frequency and intensity, each applied in a rotational grazing system. These quality factors were also evaluated for a simulated continuous grazing (CG) system. Low frequency, low intensity grazing produced lower CDMD and herbage N levels than higher grazing frequencies and intensities. These differences were, however, generally small. Overall, levels of herbage digestibility (estimated by CDMD) and N fell within similar ranges to those observed for perennial ryegrass in temperate environments. Seasonal trends in quality were characterized by high levels during late autumn to early summer (May to October) and low levels during mid‐summer to early autumn (January to April). These data would tend to support high frequency grazing as part of the management programme for perennial ryegrass. It is cautioned, however, that for subtropical conditions in South Africa, adopting frequent grazing may reduce persistence of perennial ryegrass.     

Feed Intake and Performance of Sheep Grazing Semiarid Grassland in Response to Different Grazing Systems

Effects of grazing management systems (GS) on biomass production and nutritional quality of rangeland vegetation in semiarid regions are extensively studied; however, limited information is available regarding their effects on diet digestibility and feed intake of grazing livestock. We therefore analyzed digestibility of ingested organic matter (dOM), organic matter intake (OMI), and live weight gain (LWG) of sheep in a grazing experiment established in the Inner Mongolian steppe of China, where two GS were tested for six different grazing intensities (GI) from very light to heavy grazing. For the continuous grazing system, sheep grazed the same plots each year, and for the alternating system, grazing and hay making were alternated annually between two adjacent plots. In July, August, and September 2009 and 2010, feed intake and live weight of sheep were determined. The GS did not affect dOM (P = 0.101), OMI (P = 0.381), and LWG of sheep (P = 0.701). Across both GS LWG decreased from 98 g · d^-1 for GI1 to 62 g · d^-1 for GI6 (P &spilt; 0.001; R² = 0.42). There were no interactions between GS and GI for all measured parameters (P ≥ 0.061), indicating that alternating grazing did not compensate for negative effects of heavy grazing even after 4 yr of grassland use. In summary, our study showed that irrespective of GI, alternating grassland use does not improve dOM, OMI, and hence, LWG of sheep. However, it might enhance revenues and ecological sustainability in the long term when compared to the common practice of continuous grazing at very high stocking rates.     

短期放牧强度对典型草原土壤有机碳及pH值的影响

选择克氏针茅典型草原放牧的西门塔尔牛为研究对象,分析研究短期不同放牧强度（零放牧、轻牧、中牧、重牧）对草地土壤有机碳及pH值的影响,以探索典型草原适宜的载畜率。结果表明：①0～20 cm土层,有机碳含量随着放牧强度的增大而降低,且在重度放牧条件下呈显著差异;而20～30 cm土层,有机碳含量大小顺序为重牧>中牧>零放牧>轻牧,且重牧与轻牧呈显著差异。②土壤pH值随着放牧强度的增大而显著增加。③垂直分布上,土壤有机碳含量随着土层深度的增加而减少,而pH值大小顺序均呈现为10～20 cm>20～30 cm>0～10 cm。由此可见,制定适宜的载畜率,维持土壤养分平衡,是遏制草地退化的必要措施。     

划区轮牧和季节连牧的比较试验

本试验于1985年6月至1987年5月在内蒙古农牧学院哈雅教学牧场,选用成年杂种羯羊对短花针茅荒漠草原划区轮牧和季节连牧进行了比较试验,旨在探讨荒漠草原地区适宜的放牧制度,合理利用天然草地。研究结果表明,划区轮牧的草群盖度显著高于季节连牧(P<0.05),牧草质量较季节连牧好;划区轮牧和季节连牧的土壤物理性状没有明显差异(>0.05);划区轮牧的绵羊比季节连牧有较长的休息时间和较短的采食、游走时间(P<0.05或 P<0.01);放牧第三年,划区轮牧的绵羊夏秋增重量显著高于季节连牧(P<0.01)。     

Seasonal influence on diet selection of sheep grazing a weedy dryland lucerne pasture

The experiment was conducted to determine the seasonal effects on the availability, chemical composition and digestibility of a grazing dry-land lucerne pasture, as measured on samples either collected by hand or with oesophageally fistulated (OF) sheep. The pasture was monitored monthly for a period of thirteen months. An overall mean amount of 647 kg DM ha^?1 of material was monitored during the experimental period. Lucerne, as a percentage of the total DM availability was relatively low (approximately 19%), probably due to the preference of sheep to select lucerne in spite of the other available material. Both the crude protein (CP) content and the organic matter (OM) digestibility of the samples showed a seasonal tendency with higher values during the winter and lower values during the summer. Mean OM, CP, organic matter digestibility (OMD), acid detergentfibre (ADF) and neutral detergent fibre (NDF) contents of 91.7%, 10.7%, 57.5%, 47.1% and 74.0%, respectively, were obtained with hand-clipped samples, while the corresponding composition of samples collected by OF sheep was 83.1%, 21.0%, 64.7%, 38.2% and 58.4%, respectively. The sheep were able to select forage samples with a higher CP content than those collected by hand throughout the year. This was, however, not the case with the organic matter digestibility of the samples during the growing season July to October. The CP content of fistula extrusion samples (f) could be predicted from hand-clipped samples (h) from the linear relationship, CP_f = 10.51 + 0.97CP_h (r = 0.59). The study provided figures on the chemical composition and digestibility of dryland lucerne pasture at grazing in a Mediterranean environment.     

宁夏滩羊放牧系统草地利用率及草畜平衡性研究

2003年5-10月在宁夏盐池荒漠草地进行了滩羊放牧强度试验,测定了宁夏滩羊采食量、采食率和草地产草量,以期确定草地适宜利用率,为解决宁夏草地全面禁牧后的重新利用提供依据。结果表明,在整个放牧季,草地现存量波动明显,放牧强度对试验区荒漠草地现存量峰值的出现时间及出现次数有明显影响;滩羊日采食量与放牧强度呈负相关,其回归方程为:y=2.04-0.54x (R²=－0.85,n=55)。滩羊采食量呈现先增加后减少趋势,具有周期波动特性;滩羊采食率在整个放牧季呈单峰变化趋势;试验草地的适宜利用率为10%～15%。实践中,不能仅依靠草地现存量去确定草地载畜量,这往往会被草地现存量“过剩”的假象所迷惑,造成草地超载、退化。     

放牧绵羊牧食行为与生产性能的研究

该试验在内蒙古锡林郭勒草原沙质草地放牧条件下,分别对4月龄和6月龄杂种羊、引种羊和蒙古羊的牧食行为、生产性能以及羊肉品质进行了比较研究,并探讨了年龄对绵羊生产性能与肉品质的影响。     

Intake of trichostrongylid larvae by goats and sheep grazing together

SUMMARY Cashmere goats and Merino sheep were grazed together at 7.5 animals per ha on annual rye grass and clover pasture in southern Victoria, a winter rainfall area. Intake of parasitic larvae was measured in oesophageal extrusa samples collected from 2 animals of each species, 4 times in one week, on 7 occasions between mid-March (autumn) and mid-June (winter). Pasture contamination with larvae was measured at the same times. The number of larvae per kg of green grass was lower than on green clover; the most heavily contaminated portion of the pasture was the mat of dead herbage on the ground. The diet selected by goats contained more green grass and dead herbage and less clover that that of sheep (P < 0.01). Goats ingested 643 infective trichostrongylid larvae per kg dry matter intake (DMI) versus 274 per kg DMI for sheep in autumn, increasing to 1892 versus 1143 in early winter. The heavier trichostrongylid burdens of goats compared with sheep, when grazed together, are due in part to greater rates of infection consequent on different grazing patterns as well as greater susceptibility to infection.     

放牧家畜养分消化率的测定

放牧家畜养分消化率反映牧草供给量和营养品质、家畜的健康状况以及生产性能等，是草原管理的关键指标之一。放牧家畜养分消化率的测定方法主要有直接测定和间接估测两种，直接法包括全收粪法、指示剂法、近红外光谱法（NIRS）等，间接法主要有体内或体外发酵法、牧草品质和气候等预测法。全收粪法是较精确的测定方法，然而耗时、费力，对家畜放牧行为有较大影响，难以体现牧场饲草供给的空间异质性；指示剂法根据不溶物的回收比例估测养分消化率，对家畜放牧行为干扰较小，指示剂不易收集，也不适于野性较高的放牧动物；NIRS法效率高、劳动强度低、成本小、不影响家畜，能够大尺度地估测放牧家畜的养分消化率，需要大量的实测数据完善预测模型；气候估测法快捷、省时，精确性较差，适于大时空尺度。放牧家畜的养分消化率与家畜、草地、放牧方法、温度、降水等生物因子，环境因子和社会因子密切相关，与遥感、无人机（UAV）和人工智能等结合，可以准确、快速地测定放牧家畜养分消化率，为草地生态修复与健康管理提供支撑。     

放牧对黑麦草＋白三叶混播草地植被构成的作用

通过4个放牧强度（轻牧、适牧、重牧和过牧,牧后草层高度分别为7.5、5.5、3.5和<2.0 cm）的轮牧试验,对黑麦草(Lolium perenne)、白三叶(Trifolium repens)混播草地土壤化学特性;黑麦草分蘖和白三叶匍匐茎、叶片数及其茎叶构成,牧草高度、生物量与植被构成进行系统研究。结果表明,土壤速效养分含量对放牧强度响应较大,稳定性较弱。随放牧强度的增加,黑麦草分蘖密度和叶片生物量显著增加,黑麦草分蘖质量和白三叶匍匐茎密度及牧草高度和生物量显著下降;黑麦草叶片数,白三叶叶片数、茎叶比和匍匐茎质量在放牧强度间无显著变化。放牧强度在降低黑麦草和白三叶生长特性整齐度的同时,增加其可塑性生长;黑麦草对放牧强度的响应比白三叶敏感,但白三叶的可塑性生长比黑麦草的高。鸭茅（Dactylis glomerata）和非播种植物种的生长特性在放牧强度内变异系数较大。综合分析认为,放牧对草地植被的作用体现于植物个体、种群和群落3个水平,播种的低组分禾草（鸭茅）和非播种禾草是混播草地植被构成变化的关键种。     

科尔沁沙质草地禾本科植物主要功能类型对连续放牧的反应

为了正确评价连续放牧对禾本科牧草的影响,在科尔沁典型沙质草地,设置不同放牧强度的4块样区,连续放牧4年后对各样区植被中禾本科植物的盖度和高度进行了样方调查,分析了3个禾本科植物功能类型.结果表明:1)禾本科植物的平均盖度对重牧比较敏感,而在中牧区、低牧区和对照区差异较小;2)3个功能类型植物的高度随放牧强度的增加,呈有规律的降低.而且多年生牧草的高度对放牧强度最敏感,一年生优质牧草次之,一年生劣性牧草最不敏感;3)多年生牧草在各样区的相对盖度随放牧强度的增加,逐渐减少,在重牧区仅为0.69%;一年生优质牧草在各样区的相对盖度表现为中牧区＞低牧区＞重牧区＞封育对照区,说明放牧干扰有提高此相对盖度的影响;一年生劣性牧草在各样区的相对盖度随放牧强度的增加,逐渐增大.     

内蒙古典型草原主要草食动物食性及其营养生态位研究——以羊草群落为例

为探讨典型草原主要食草动物(绵羊、达乌尔黄鼠和亚洲小车蝗)的食性及其种间生态位变化与草原退化的关系,以内蒙古典型草原为研究对象,于2003年7-8月运用饱和链烷技术研究羊草群落不同放牧强度下绵羊、达乌尔黄鼠和亚洲小车蝗的食性及其生态位变化。结果表明,随牧压的增大,群落中羊草和克氏针茅的数量减少,星毛委陵菜比例增加;随牧压的增加,绵羊采食黄囊苔草的比例显著增加,在重度放牧区,绵羊没有采食西伯利亚羽茅和米氏冰草,而是增加了对星毛委陵菜的采食;达乌尔黄鼠在围栏内采食羊草的比例显著高于围栏外放牧区;但在围栏内没有采食米氏冰草、黄囊苔草和星毛委陵菜;围栏内无法捕捉亚洲小车蝗,在放牧区亚洲小车蝗对克氏针茅的采食随牧压的增加显著降低,但增加了对米氏冰草和星毛委陵菜的采食。三者同时采食羊草和糙隐子草,且对羊草的选择性指数最高;随牧压的增大,绵羊的生态位宽度变宽,而达乌尔黄鼠和亚洲小车蝗的生态位宽度变窄,三者生态位重叠程度类似。因此,重度放牧改变了羊草群落的植被组成,使其演替为星毛委陵菜群落,从而导致了草地的退化,而鼠类和蝗虫的危害则加剧了草地的退化演替,三者对草地资源的共同掠夺导致草原严重退化。     

不同放牧率对草原牧草再生性能和地上净初级生产力的影响

在生长季研究不同放牧率对草原牧草再生性能和地上净初级生产力的影响。结果表明,随着放牧率的增大,地上现存量呈线性下降,但地上净初级生产力(地上现存量＋家畜采食量)以2.67只羊/hm²处理最大,即存在超补偿性生长。地上最大现存量和最大净初级生产力出现的日期随着放牧率的增大有提前的趋势,二者随着放牧年限的延长均有较大幅度的下降。但降水可以缓和或加剧此变化的趋势。在冷蒿小禾草退化草原上,1.33和2.67只羊/hm²始牧时期为5月中下旬为宜,而重度放牧宜在6月上、中旬;重牧或过度放牧可降低牧草早期的再生能力,但可加快后期的再生速度,即后期牧草补偿性生长较明显。     

放牧强度对不同草地类型生态系统气体交换影响的研究

为揭示不同放牧强度下不同草原类型气体交换的变化规律,在8月中旬采用Li-6400 便携式光合仪和密闭式箱法,分别对内蒙古草甸草原、典型草原和荒漠草原不同放牧强度下气体交换进行分析研究。结果表明:不同草原类型之间的生态系统净CO₂交换(NEE)、生态系统总呼吸(ER)和生态系统总初级生产力(GEP)均存在显著差异(P<0.05)。草甸草原的NEE和GEP随放牧强度增加呈现降低趋势,ER则呈现上升趋势;典型草原的NEE和GEP随放牧强度增加呈现上升趋势,ER则呈现下降趋势;荒漠草原的NEE和GEP除对照区外,随放牧强度增加呈现上升趋势,而ER呈降低趋势。放牧通过对草原生态系统植物、土壤等产生影响,从而影响生态系统气体交换。