Grazing and grazing management terminology in southern Africa

In order to avoid misunderstanding arising in discussions and from the literature on grazing management problems in Southern Africa a proposed list of terms and definitions to cater for all grazing situations and concepts is presented. The terms are classified into two groups, those dealing with properties of the vegetation and those dealing with aspects of management. The former group includes veld, fynbos, karoo, grassveid, bushveld, sourveld, swectveld, pastures, leys, permanent pastures, cultivated pastures, introduced pastures, species selective grazing, area selective grazing, grazing capacity, current grazing capacity and potential grazing capacity. Some of these terms are well known to pasture scientists in Southern Africa and their inclusion here is largely to facilitate understanding by overseas readers of the literature from this sub‐continent. Those terms dealing with aspects of management are continuous grazing, rotational grazing, rotational resting, rotational grazing and resting, zero grazing, stocking rate, stocking pressure, stocking density, stocking density index, period of occupation, period of stay, stocking intensity, period of rest and resting intensity. Many of these terms are not in current use in Southern Africa. They nevertheless are related to important concepts in grazing management deserving of greater attention.     

围栏禁牧与放牧对草地生态系统固碳能力的影响

草地生态系统固碳能力对全球碳贮量的大小有重要影响。放牧作为草地最广泛的利用方式之一影响着草地的碳贮量,过度和不合理的放牧方式造成草地退化,引起草地碳的损失。围栏禁牧与放牧对草地生态系统固碳能力的影响主要包括对植被生产力和土壤碳贮量的影响,本文对有关的报道进行了综述。结果显示,由于受植被凋落物、群落结构和气候等多因素的影响,围栏禁牧对草地植被生产力有正面或负面的效应;放牧对植被生产力的影响也没有一致的结果,此外,放牧对植被生产力的影响还与放牧的强度有关。围栏禁牧与放牧可以通过多种途径对草地土壤碳贮量产生正面或负面的影响。总之,围栏禁牧与放牧对草地生态系统固碳能力的影响是复杂多样的,需要对草地碳贮量进行估算,并对相关的机制进行研究,这样才能在草地管理方面做出合理的决策。     

Aardvark burrows: a potential resource for animals in arid and semi-arid environments

Arid and semi-arid environments are characterized by extreme fluctuations in temperature and low rainfall, which present significant challenges to the animals inhabiting these areas. However, the presence of burrows may allow animals to avoid climatic extremes and predators and may act as valuable foraging sites. We assessed the microhabitat conditions (maximum and minimum temperature, relative humidity and seed abundance) of aardvark (Orycteropus afer) burrows in relation to paired non-burrow areas at three sites in South Africa. We also describe the extent to which they are used as resources by other vertebrates. Maximum temperatures were significantly lower and minimum temperatures and relative humidity values were significantly higher inside the burrows than outside. The concentration of seeds inside the burrows and at the paired non-burrow sites was similar. Twenty-seven vertebrate species (21 mammals, two birds, three reptiles and one amphibian) were recorded making use of the burrows and it is likely that these species accrue benefits (e.g. a buffered microclimate) from burrow use. However, our sampling was biased towards mammals and nocturnal species. Consequently, we recommend further work to establish the overall reliance of vertebrate taxa on aardvark burrows in arid and semi-arid environments.     

Determining spatial and temporal variability in quantity and quality of vegetation for estimating the predictable sustainable stocking rate in the semi-arid savanna

This study assessed the importance of spatial and temporal variation in plant quality and quantity for determining sustainable stocking rates in game, commercial and communal ranches in semi-arid savanna of the Northern Cape Province, South Africa, in wet and dry seasons over a two-year period. We focussed on variation in plant biomass, phosphorus (P), crude protein (CP) concentrations and dry matter digestibility as parameters most likely to affect sustainable stocking rates. Habitat type had greater effects on plant quality, plant biomass and species composition than management type. The commercially-managed area had the highest tree density in the rocky habitat and lower plant quality than other management types. All of these features indicate that land degradation is occurring on commercial ranches in spite of rotational grazing and lower stocking density than on communal ranches. We recommend that commercial ranchers should introduce a greater variety of stock and/or game to reduce selective grazing of certain plant species. Quality measures (CP and P) gave more conservative predictions of stocking density than biomass. In this region of the Northern Cape, seasonally-inundated pan habitats are particularly valuable in spite of low-standing crop because they have the highest year-round quality. Contrastingly, ranchers should only lightly stock open savanna habitats, in spite of high standing biomass, because they have low vegetation quality and may be particularly susceptible to degradation and invasion by poisonous and unpalatable plants.     

青藏高原天然草场放牧家畜体重和体能量变化动态

用逐月称重法和季节屠宰试验获得青藏高原放牧家畜的体重和体能量沉积的季节动态。结果表明 ,放牧家畜在出生后第 1个冷季的体重下降幅度远低于第 2个冷季 ,高山细毛羊在暖季每千克增重的能量水平保持稳定 ,尽管秋季略有下降 ,但与夏季相比 ,差异不显著 ;牦牛在秋季每千克增重的能量则远高于夏季。牦牛和高山细毛羊在冬季每千克减重的能量水平远高于春季。牦牛和高山细毛羊在第 2个暖季所积累的能量约有一半以上在第 2个冷季被消耗     

放牧家畜采食量和采食成分测定技术评述

放牧家畜的采食量是人们了解放牧系统动力学的关键之一。研究已查明,了解了放牧家畜的采食量和采食成分就能明晰家畜的营养状况,预测其生产性能,从而为草地管理决策提供目标,为优化资源利用提供基础数据。然而,估测放牧家畜的采食量及其组分是困难的,也是昂贵的。虽然那些改进的技术和方法有效地增强了人们获取家畜牧食行为数据的能力,但是测定放牧动物的采食量、采食成分和养分消化率一直以来都是营养学研究的挑战,方法众多,却各有利弊。因此,本研究针对目前估测放牧家畜采食量和采食成分的常用方法,如模拟采食法、牧前牧后差额法、酸不溶灰分法、三结合法、植物蜡层指示剂法和近红外光谱技术法,对它们的利弊和准确性进行讨论,并探析未来发展趋向,为今后的研究提供资料。     

肃南山地放牧系统四季供需动态模型

通过分析和综合肃南山地放牧系统的四季放牧试验数据,模拟了该系统的牧草供给与家畜需求的季节动态,用模式图反映了放牧系统牧草供需平衡机理。通过分析放牧系统的时间地带性的生态要素,拟合了肃南山地放牧系统的放牧函数,并建立了北半球中纬度地区的一般方程。这些模型数量化地解释了“生物的时间地带性”理论在山地放牧系统牧草供给与家畜需求平衡中的作用,对放牧管理和畜牧业持续发展具有一定的指导作用。     

放牧强度对温性荒漠草原土壤全氮和有机质的影响

对3个不同放牧强度下温性荒漠草原不同土层土壤有机质和全氮含量进行了测定。结果表明,温性荒漠草原土壤全氮和有机质含量随土壤深度的加深而减少;随着放牧强度的加大,各土层全氮和有机质含量均降低;相关分析结果表明,3种放牧强度下土壤全氮和有机质含量均呈极显著正相关,表明土壤全氮含量随土壤有机质的增加而增加。     

Macro and trace elements of 26 browse species growing in semi-arid grazing lands of Eastern Cape,South Africa

ABSTRACT

Leaves and twigs from woody plants provide essential nutrients to range animals. We examined variation in the mineral status of 26 woody species, and the influence of harvesting height as well as the interactions of the main effects on minerals levels. Leaves were harvested from five individual plants per species at two height levels: low (<1 m) and upper (>1.5 m). For trees, all mineral levels showed variation (p < 0.05) between species. For shrubs and intermediate growth forms (between shrubs and trees), mineral levels except potassium (K) and zinc (Zn) were influenced (p < 0.05) by height × species interactions. Most browse species had calcium (Ca) contents (8.5–50 g kg^-1) above the required levels, with the majority of the species having Ca beyond the maximum tolerable limit. Most browse plants had sufficient K, phosphorus, magnesium, manganese, iron and Zn concentrations to meet the requirements for ruminants. Copper was deficient in many browse leaves, thus supplementation should be considered in winter. We conclude that such knowledge is essential for sustainable use of browses as mineral supplements, especially during critical periods when climatic conditions limit the feed value of grasses.     

Livestock grazing has minimal effect on the species richness and diversity of semi-arid shrubland in the Western Little Karoo,South Africa

The Succulent Karoo, one of two arid biodiversity hotspots in the world, is known for its high plant species richness, but little is known about the influence of topography and how it mediates the potentially deleterious effects of grazing. Changes in vegetation species composition, cover and species diversity were examined along piosphere gradients on northerly slopes, bottomlands and low-lying plains on 45 farms. Landscapes differed in the plant speciesand life-form composition, species richness and cover, with the more species-rich, heterogeneous grassy northerly slopes distinct from the plains and bottomlands, which were dominated by Pteronia pallens, Psilocaulon junceum and Drosanthenum spp. with more annual and ephemeral species. Overall, species richness declined linearly with decreasing rangeland condition. A weak grazing effect was detected only on the north-facing slopes, where shrubs and grass decreased with intense grazing. Years of overgrazing have resulted in the widespread dominance of P. pallens, especially on the plains and bottomlands, rendering them insensitive to grazing. The current condition of the northern slopes should be maintained and managed such that palatable species can spread to more degraded areas of the landscape.     

The impacts of season and livestock management strategy on the quality of diets selected by goats and sheep in the semi-arid rangelands of Namaqualand,South Africa

Access to good-quality forages is one of the major limitations to livestock production in semi-arid pastoral systems. This study aimed to determine whether there are differences in the nutritional quality of diets selected by herded and free-ranging goat and sheep flocks utilising Namaqualand Granite Renosterveld vegetation during the wet and dry seasons. Plant samples collected along the grazing routes of livestock were dried and analysed for their fibre, condensed tannin, total phenolic and mineral nutrient contents. The study showed that a large variety of forages were on offer and livestock groups selected different diets of which some were different to the total diet on offer. In general, significant deficiencies in phosphate, protein and energy in the diets selected by herded and free-ranging goats and sheep were observed in both wet and dry season. The quality of the diets selected by herded and free-ranging livestock was also found to be different from each other, with herded livestock generally selecting more nutrient-dense diets. Herding, therefore, allows livestock to access better-quality forage in the Namaqualand Granite Renosterveld rangeland, where it is generally poor.     

Effect of using Acacia mearnsii tannin extract as a feed additive on nutritional variables and productive performance in dairy cows grazing a temperate pasture

This study was carried out to evaluate the impact of including Acacia mearnsii tannin extract (TA) as a feed additive on nutrition and productive performance of dairy cows grazing a high‐quality temperate pasture and receiving supplementation with a concentrate feedstuff. Fourteen multiparous Holstein cows were assigned to either of the following treatments: concentrate without or with 20 g TA/kg dry matter (DM). Concentrate intake accounted for 32% of the total DM intake. Tannin addition increased the herbage DM intake by 22% (p < .05). There was no effect of TA inclusion on milk yield, milk composition, milk nitrogen (N) excretion, milk and plasma urea‐N concentration, urinary excretion of total N, urea‐N, and purine derivatives. However, TA inclusion increased the N intake and retention, total N excretion in manure, fecal N to urine N ratio, and decreased the dietary N efficiency for milk production and the percentage of ingested N excreted in urine (p < .05). In conclusion, supplementing dairy cows grazing a high‐quality temperate pasture with a concentrate containing 20 g TA/kg DM showed the potential of decreasing the proportion of ingested N excreted in urine without affecting the productive performance.     

Prevalence of bovine tuberculosis and animal level risk factors for indigenous cattle under different grazing strategies in the livestock/wildlife interface areas of Zambia

A cross-sectional study was conducted to investigate the prevalence and animal level risk factors for bovine tuberculosis (BTB) in indigenous cattle of the livestock/wildlife interface areas in Zambia. A total of 944 cattle from 111 herds were investigated. The comparative intradermal tuberculin test (CIDT) was used to identify reactor animals for BTB. Animal level data on sex, age, parity and body condition score were registered. The overall animal prevalence of BTB as determined by the CIDT was 6.8% (95% CI: 4.2, 9.5%). In Lochinvar and Blue Lagoon areas, animal level prevalence were observed at 5.2% (95% CI: 2.2, 8.2%) and 9.6% (95% CI: 6.1, 13.2%), respectively. Kazungula, an area outside the livestock/wildlife interface, had a prevalence of only 0.8% (95% CI: 0.0, 2.3%). The age of the animal, its body condition score and the type of management system, were predictive of its BTB status. The study revealed that BTB was relatively high in the livestock/wildlife interface areas of Lochinvar and Blue Lagoon compared to Kazungula. These findings should raise a serious public health concern considering the extent to which the communities of the study areas are in contact with their animals and the levels at which they use untreated milk.