Influence of stocking rate and grazing systems on available grazing in the northern cape 1

Abstract

The influence of rotational and continuous grazing systems, each applied with four stocking rates, on the above‐ground phytomass of veld was determined over four years.

Grazing systems showed a significant influence on available herbage during one year only. Increased stocking rates brought a progressive decline in above‐ground phytomass. During the fourth season (1980/81) the average grazing pressures at stocking rates of 10 ha, 7 ha, 5,5 ha and 4 ha/Large stock unit were 5 984 kg, 3 417 kg, 2 390 kg and 1 238 kg and 1 238 kg phytomass/Large stock unit, respectively. At the end of the fourth season (July, 1981) there was reserve grazing available on the various stocking rates for approximately 579 days, 337 days, 202 days and 76 days, respectively. The risk of high stocking rates in the marginal rainfall regions, is emphasised.     

Comparison of Season-Long Grazing Applied Annually and a 2-Year Rotation of Intensive Early Stocking Plus Late-Season Grazing and Season-Long Grazing

This research measured steer gains, aboveground biomass remaining at the end of the growing season, and economic returns of tallgrass prairie grazed under season-long stocking (SLS-C) and a grazing system that included a 2-yr rotation of SLS-rotated (SLS-R) and intensive early stocking (IES; 2× normal stocking rate) + late-season grazing at the normal stocking rate (IES + LSG-R). We hypothesized that even though the stocking rate on the IES + LSG-R pasture was above the recommended rate, the greater regrowth availability in the late season would result in steers gaining as well as or better than those stocked SLS at the normal rate. By rotating the IES + LSG treatment with SLS over 2 yr, we anticipated that the aboveground biomass productive capacity of the IES + LSG pasture would be restored in one growing season. Further, we hypothesized that the increased stocking rate with IES + LSG would increase net profit. Comparing traditional season-long stocking to the system, which was a combination of SLS and IES + LSG rotated sequentially over a 2-yr period, the system increased steer gains by 7 kg · hd^?1 and by 30 kg · ha^?1, had a consistent reduction of 429 kg · ha^?1 biomass productivity, and increased net profit by $55.19 per steer and $34.28 per hectare.     

A model for predicting livemass gain from stocking rate and annual rainfall

Abstract

The relationship between livemass gain and stocking rate was established for young beef animals grazing kikuyu and Coastcross II pastures in each of five grazing seasons. The annual rainfall within these seasons ranged from 506 mm to 990 mm. Relationships between pasture production variables and annual rainfall are described and these are used to construct a model for predicting livemass gain/ha/season for different stocking rates and levels of annual rainfall.     

Prescribed Fire,Grazing, and Herbaceous Plant Production in Shortgrass Steppe

We examined the independent and combined effects of prescribed fire and livestock grazing on herbaceous plant production in shortgrass steppe of northeastern Colorado in the North American Great Plains. Burning was implemented in March, before the onset of the growing season. During the first postburn growing season, burning had no influence on soil moisture, nor did it affect soil nitrogen (N) availability in spring (April–May), but it significantly enhanced soil N availability in summer (June–July). Burning had no influence on herbaceous plant production in the first postburn growing season but enhanced in vitro dry matter digestibility of blue grama (Bouteloua gracilis [Willd. ex Kunth] Lag. ex Griffiths) forage sampled in late May. For the second postburn growing season, we found no difference in herbaceous plant production between sites that were burned and grazed in the previous year versus sites that were burned and protected from grazing in the previous year. Our results provide further evidence that prescribed burns conducted in late winter in dormant vegetation can have neutral or positive consequences for livestock production because of a neutral effect on forage quantity and a short-term enhancement of forage quality. In addition, our results indicate that with conservative stocking rates, deferment of grazing during the first postburn growing season may not be necessary to sustain plant productivity.     

Stocking rate and the productivity of Rhodes grass pastures on the Lilongwe plain,Malawi

An experiment was undertaken over three wet (summer) seasons to investigate the effects of different set stocking rates on animal performance from fertilised Rhodes grass pastures. The three set stocking rates were 2.5, 5 and 7.5 livestock-units/ha (1 livestock unit=342 kg liveweight). Pasture productivity was related to stocking intensity. Animal gain per hectare was directly related to stocking rate. Gain per animal, gain per livestock unit and number of grazing days were all inversely proportional to stocking rate. Animals on the low stocking rate were carried through almost to the end of the dry (winter) season with only small changes in liveweight. The practical significance of the results is discussed.     

Vegetation Production Responses to October Grazing in the Nebraska Sandhills

Understanding the long-term effect of summer grazing date and fall stocking rate on herbage production is critical to extending the grazing season in the Nebraska Sandhills. A study was conducted from 1997 to 2002 at the Gudmundsen Sandhills Laboratory located near Whitman, Nebraska, to determine the herbage production response to summer grazing date and October stocking rate on two different sites. Site 1 was dominated by warm-season grasses and site 2 was dominated by cool-season graminoids. At each site, three 0.37-ha pastures were constructed in each of four blocks before application of summer grazing treatments. Pastures in each block were grazed at 0.5 animal-unit months (AUM) · ha^?1 in June or July, or were deferred from summer grazing. Following summer grazing treatments, October stocking rate treatments (no grazing or 1.0, 2.0, or 3.0 AUM · ha^?1) were applied to subunits of each summer grazing date pasture during mid-October. Vegetation was sampled in each pasture in mid-June and mid-August and sorted by functional group to determine the effect of 5 yr of grazing treatments on herbage production and residual herbage. Herbage production was not affected by summer or October grazing treatments on the warm-season grass–dominated site. Increasing October stocking rate, however, reduced cool-season graminoid production and subsequent herbage production 25% by year 5 of the study. Residual herbage at both sites at the end of the October grazing periods explained as much as 16% to 34% of subsequent year’s herbage production. Grazing managers in the Nebraska Sandhills can extend the grazing season by lightly stocking pastures in the summer to facilitate additional fall grazing. Heavy stocking in October over several years on cool-season–, but not warm-season–, dominated sites will reduce production of cool-season graminoids on these sites.     

划区轮牧与草地可持续性利用的研究进展

划区轮牧是一种充分利用饲草生长旺季而进行的集约、区块式放牧管理系统。本文总结了近年来国内外轮牧制度的发展现状,概括了划区轮牧的优势包括:提高草地生态系统的功能性、草地生产力;降低草食动物肠胃线虫感染率;分析了其与传统连续放牧相比所具有的局限性。进一步从放牧类型的延展、放牧策略的改进、人为因素的投入、生态模型研究等多角度综合考究,提出综合协调生物因素与环境、平衡生态与经济以及优化牧企合作现状的轮牧策略,以期为轮牧对于生态恢复和草地可持续性利用的生产实践应用提供科学依据和优化管理的决策参考。     

Long-term cattle gain responses to stocking rate and grazing systems in northern mixed-grass prairie

The effects of stocking rate and grazing system on gains of yearling beef cattle grazing rangelands have largely been addressed in short-term (< 10 years) studies, and often stocking rates are confounded within grazing systems with higher stocking rates for short-duration rotational grazing systems compared to season-long grazing. A grazing system (season-long and short-duration rotational grazing) × stocking rate (light: 16 steers/80 ha, 18.0 animal unit days/ha; moderate: 4 steers/12 ha, 30.1 animal unit days/ha; and heavy: 4 steers/9 ha, 40.1 animal unit days/ha) study was initiated in 1982 on northern mixed-grass prairie. Here, we report on the final 16 years (1991–2006) for yearling beef cattle gains. Average daily gains (kg/head/day) across all years with season-long grazing decreased with increasing stocking rate and grazing pressure. Heavy stocking rates reduced average daily gain by 16% and 12% compared to light and moderate stocking rates, respectively. In contrast to average daily gain, beef production (kg/ha) increased with increasing stocking rate and grazing pressure. Cattle gains were reduced by 6% with short-duration rotation compared to season-long grazing over the study period, with differences between systems observed in years with average, but not dry or wet, spring (April + May + June) precipitation. Grazing season gains (kg/head) and beef production both exhibited significant increasing hyperbolic relationships with spring precipitation, with the percentage of variation explained by spring precipitation substantially higher (62–83%) for beef production compared to grazing season gains (32–45%). The influence of spring precipitation on cattle gains suggests that incorporation of these relationships into modeling efforts for strategic planning and risk assessment will assist land managers in better matching forage and animal resources for greater sustainability in this highly variable environment.     

Vegetation responses to seasonal weather conditions and decreasing grazing pressure in the arid Succulent Karoo of South Africa§

The Succulent Karoo biome is a renowned centre of biodiversity and endemism in the arid winter rainfall region of South Africa that is threatened by climate change. On 20 permanently marked plots within a biodiversity observatory, species richness and cover were assessed annually from 2002 to 2017 during the growing season. We were interested, firstly, in whether the vegetation showed any trends in response to the strong decrease in grazing pressure, which occurred at the beginning of the monitoring period, and secondly, in the effect of seasonal climate on the vegetation. We analysed the responses of species richness and cover in four life forms to seasonal rainfall and the standardised precipitation–evapotranspiration index (SPEI) using linear mixed-effect models. Time had a positive effect on richness of annual species and a negative effect on cover of shrubs and annuals, which increased in response to SPEI and less strongly to rainfall during autumn and winter. Habitat did not have any effect and geophytes and perennial herbs did not show any significant response. The importance of SPEI during autumn and winter is discussed in relation to potential germination cues and the projected decrease in rainfall and increase in temperature during these seasons.     

牦牛放牧率对江河源区混播禾草地上初级生产量及种间竞争力的影响

在江河源区2龄混播禾草草地(垂穗披碱草 星星草)上牦牛放牧试验结果表明: 随着放牧率的增加,在生长期内不同功能群地上净初级生产量和总地上初级生产量均出现了单峰曲线变化,即“S”型变化趋势; 总的地上净初级生产量和垂穗披碱草地上净初级生产量对放牧率的变化很敏感, 且随着放牧率的增加, 峰值出现日期提前; 其它禾草和星星草的峰值对放牧率的变化不很敏感;莎草类和杂草类对放牧率的变化比较敏感。随放牧率的增加, 地上现存量和总地上初级生产量的峰值下降, 且达到峰值的时间提前。在整个放牧期(植物生长期),重度放牧的RYT值均小于1,表明重度放牧使垂穗披碱草和星星草一直处于拮抗状态,其它各处理组在生长中后期也处于拮抗状态; 不同放牧率(包括对照)下垂穗披碱草的竞争力强于星星草, 垂穗披碱草因其高度和发达而较深的根系成为竞争的优胜者。     

短花针茅荒漠草原土壤氮素矿化对载畜率的响应

氮矿化是决定土壤提供可利用性氮的关键生态环节,同时也是当今国内外土壤氮素循环的研究热点,荒漠草原作为草地生态系统中极特殊的一种草地类型,其资源贫乏,气候严酷,植被结构相对简单,因此研究荒漠草原氮素的可利用性对维持荒漠草原稳定发展十分必要。鉴于此,本研究以内蒙古四子王旗短花针茅荒漠草原为对象,采用顶盖埋管培养法,通过在整个生长季的跟踪调查,主要探讨了净氮矿化速率对4个载畜率梯度[0(对照)、0.91(轻度放牧)、1.82(中度放牧)、2.71(重度放牧)羊/(hm²·a)]的响应,并结合土壤温湿度,分析其与土壤氮矿化的关系,旨在为荒漠草原生态系统氮素可持续利用的研究提供基础数据及管理参考。结果显示,土壤的净氮矿化速率在整个生长季呈现出先降后增的趋势,并且在生长高峰期7月及8月受载畜率的影响较大。4种载畜率梯度下中度放牧处理[1.82羊/(hm²· a)]具有最高的净氮矿化速率,重度放牧处理中[2.71羊/(hm²·a)]净氮矿化速率最低。皮尔森相关分析表明硝化速率与净氮矿化速率显著正相关,在整个生长季中净氮矿化速率受硝化作用影响较大。不同载畜率梯度下,土壤水分与净氮矿化速率极显著负相关,而土壤温度则与净氮矿化速率无显著相关性。综上所述中度载畜率水平[1.82羊/(hm²·a)]是维持荒漠草原稳定矿化速率的理想载畜率。     

Grazing pressure and acquisition of Ostertagia ostertagi in calves

The effect of stocking rate on the acquisition of Ostertagia ostertagi infection and performance of yearling calves grazing a marshland area in the southwest of Jutland (Denmark) was examined. During the early part of the grazing season, when grass growth was high and pasture infectivity low, there was little stocking rate effect on performance. However, during the late part of the grazing season (characterized by poorer grass growth and high pasture infectivity) gains were significantly lower at high, compared with moderate stocking. At both stocking rates, the beneficial effect of moving animals to aftermath in mid-summer was significant, but was most pronounced at the high stocking rate. Interactions between stocking rate and acquisition of parasitism are discussed in the light of grazing behaviour and climatic factors.     

科尔沁沙地降水量波动对草场植被组成和初级生产力影响的研究

科尔沁地区降水量变化对沙地草场植物组成和生产力影响的研究表明,在湿润年份(大于平均降水量)沙地草场的植物种丰富度较高(18～23个种)。降水量的变化对不同生活型植物重要值的影响比较大,其中降水量变化对一年生植物影响最大,多年生草本次之,灌木类最小。降水量变化对沙地生产力的影响与降水的分布格局有关,总体来看,生长期降水量对草场生产力影响最大,两者的关联度为0.927;年降水量次之,为0.893;关键期降水最小,为0.859。从不同生活型植物生产力对不同时期的降水反响来看,年降水量对多年生草本影响最大,生长期降水量对一年生植物影响最大,关键期降水量对灌木类植物影响最大。     

Rotational and continuous grazing of sheep in the Inner Mongolian steppe of China

The aim of this study was to compare the effects of rotational and continuous grazing on herbage mass (HM), organic matter digestibility (dOM) and intake (OMI) and live weight gain (LWG) of sheep grazing on the inner Mongolian steppe, China at a stocking rate of 4.5 sheep/ha during the growing season. In the years 2005 and 2006, four 2-ha plots were used of which two were divided into four 0.5 ha paddocks each for rotational grazing, where sheep were moved each 10 days to the next paddock. The dOM was estimated from faecal crude protein concentration and OMI by oral administration of titanium dioxide. Herbage mass was similar in both grazing systems and dOM and OMI were higher (p < 0.05) at continuous grazing than at rotational grazing, but LWG did not differ probably because of extra energy expenditure for grazing and walking in a larger area. The dOM and OMI decreased (p < 0.05) with progress of the growing season and differed between years. Since precipitation during the growing season in both years was lower than the 30 years average which was probably the reason that positive effects of non-grazing periods on herbage regrowth and quality at rotational grazing could not occur, further studies are required in years with average precipitations before a final evaluation of these grazing systems can be made. Moreover, it seems necessary to quantify energy expenditure for physical activity of animals in grazing studies.     

放牧率对牦牛生产力的影响初析

通过2年的牦牛放牧试验,结果表明:放牧率对牦牛生产力有显著的影响,牦牛个体增重与放牧率呈线性回归关系;在试验期内,轻度放牧组的日增重较快,中度放牧次之,重度放牧最慢,而且随着放牧率的提高,牦牛平均个体总增重依次为136.7kg,128.6kg,93.5kg,轻度放牧比中度放牧和重度放牧分别高6.3%和46.2%。经方差分析表明,3个处理的牦牛平均个体增重有显著的差异(P<0.05),进一步作新复极差测验,30%和50%之间差异不显著,但他们和70%之间的差异均显著。     

The influence of various types and frequencies of rest on the production and condition of sourveld grazed by sheep or cattle. 2. Vigour

Treatments involving a full growing season rest in alternate years, half a growing season rest (late season) in alternate years and no rest were applied to veld grazed by sheep or cattle at similar stocking rates. Residual effects of the treatments on veld vigour were determined by measuring species regrowth during the season following treatment application, compared to ungrazed controls. The vigour of veld grazed by sheep declined rapidly relative to veld grazed by cattle. The vigour of palatable species was severely impacted, vigour of intermediate species was variably impacted and vigour of unpalatable species increased dramatically on veld grazed by sheep. Similar trends occurred in veld grazed by cattle, but to a lesser degree. Resting was beneficial for vigour recovery in both sheep and cattle treatments but it seems that the grazing treatment between rests has an over-riding influence on veld vigour. The veld grazed by sheep remained at a lower productivity level than veld grazed by cattle. Principles related to resting and the impacts of sheep and cattle grazing are briefly discussed with a view to formulating management strategies.     

短花针茅草原放牧系统植物补偿性生长的研究：Ⅰ.植物净生长量

试验于１９９６￣１９９７年在内蒙古农牧学院哈雅教学牧场，研究２岁杂种羯羊在短花针茅荒漠草原不同载畜率下植物的净重复一。结果表明，１９９６年５个载畜率处理地上净生长量与对照区差异不显著（Ｐ〉０．０５），植物表现等补偿性生长。在１９９７年干旱年份，当载畜率小于２．０只羊／半年／ｈｍ＾２时，放牧区地上净生长量与对照间差异不显著（Ｐ〉０．０５），植物表现等补偿性生长。当载畜率大于２．０只羊／半年／ｈｍ＾２     

Impact of Stocking Rate and Rainfall on Sheep Performance in a Desert Steppe

Livestock performance is a critical indicator of grassland production systems and is influenced strongly by precipitation and stocking rates. However, these relationships require further investigation in the arid Desert Steppe region of northeastern China. We employed a randomized complete block design with three replications and four grazing treatments (nongrazed exclosure [Control]), lightly grazed [LG], moderately grazed [MG], and heavily grazed [HG]) by sheep in a continuously grazed system (June to November), to test the effect of stocking rate on sheep performance. The planned stocking rates were 0, 0.15, 0.30, and 0.45 sheep · ha^?1 · mo^?1, for the control, LG, MG, and HG treatments, respectively. However, actual stocking rates were calculated for each paddock in each year based on a 50-kg sheep equivalent (SE). Annual net primary production (ANPP) was determined at peak standing crop in August 2004 to 2008. Live weight gain was determined for the summer and fall periods, as well as the total grazing period, in each year. ANPP decreased with increasing stocking rate, and daily live weight gain per head decreased linearly with increasing stocking rates over the total grazing period but in a quadratic manner over the summer period with a plateau at the lower rates. Maximum sheep production per unit area over the total grazing season occurred at about 2 SE ha^?1 for about a 5-mo grazing period, but individual gains per sheep were predicted to decline after about 1 SE ha^?1 presumably because of forage limitations. However, in order to achieve stable annual production, we recommend that the Desert Steppe be grazed at about 0.77 SE ha^?1 for a 5-mo period (0.15 SE ha^?1 · mo^?1). This estimate is based on published grazing strategies that consider an average ANPP with a recommended utilization rate of 30%.     

Individual animal performance in relation to herbage mass and stocking rate in the Natal Sour Sandveld

Grazing trials were established at two sites in the Natal Sour Sandveld. The objective of this article was to present the patterns in individual animal performance in relation to herbage mass and stocking rate for the period November 1986 to September 1987. Rainfall exceeded the mean annual rainfall for Site 1 and was well below average for Site 2. Rainfall at Site 1 exceeded that at Site 2 by 329 mm. Distinct patterns in herbage mass were seen during the season. A grazing cut‐off was established at 2 000 kg/ha of herbage mass. Herbage mass seldom exceeded 2 400 kg/ha in grazed camps. A quantity limitation was evident for most of the growing season. The relationship between animal performance and stocking rate was linear but the slopes of the relationships differed.