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Acacia sieberiana DC. Small to medium tree, in wooded savannah, open forest, thicket, and grassy savannah; also wet places. C.N.: mussongue, musonge (kb). Uses: firewood, medicinal. Conservation: LC (Costa et al. 2009, 2019) F.Monteiro 799 (LUAI, LISC), Published as part of Monteiro, Francisca, Costa, Esperança Da, Kissanga, Raquel, Costa, José Carlos & Catarino, Luís, 2022, An annotated checklist of the vascular flora of Quiçama National Park, Angola, pp. 1-67 in Phytotaxa 557 (1) on page 31, DOI: 10.11646/phytotaxa.557.1.1, http://zenodo.org/record/6985699, {"references":["Costa, E., Dombo, A. & Pedro, M. (2009) Plantas Ameacadas em Angola. Centro de Botanica, Universidade Agostinho Neto, Luanda, 154 pp."]}

The study was aimed at evaluating the seeds of a leguminous plant, Acacia sieberiana DC as an alternative source of dietary plant protein for broilers. Five experimental diets containing 0 (control), 5, 10, 15 and 20% Acacia sieberiana seeds (ASS) were formulated and fed to 5 groups of birds during starter (0 - 4 weeks), grower (5 - 8 weeks) and finisher (9. -12 weeks) periods respectively. There were 3 replicates per treatment, with 10 birds per replicate. At the end of the experiment, average weekly live weight gains of 128.90 ± 24.17, 122.68 ± 25.09, 112. 79 ± 22.83, 96.40 ± 21.53 and 99.56 ± 21.53g were obtained for the birds on 0, 5, 10 and 20% ASS inclusion respectively. The average weekly feed consumption values were 413.47 ± 63.63, 408.59 ± 63.82, 304.60 ± 61.70, 347.96 ± 58.0 and 352.83 ± 59.76g for the birds on O, 5, 10, 15 and 20% ASS respectively. The feed efficiencies were 0.289 ± 0.03, 0.272 ± 0.03, 0.264 ± 0.03, 0.248 ± 0.03 and 0.253 ± 0.03 for the birds on 0, 5, 10, 15 and 20% ASS respecfrre!y. The data revealed that in general, the birds on 0, 5 and 10% ASS inclusion performed better (PC < .05) than birds on 15 or 20% ASS. Results of carcass evaluation show that the gizzard, lungs and heads of the control birds had significantly (PC < .05) higher weights than those of birds on 15 and 20% ASS. From these results it can be concluded that up to 10% ASS could be incorporated into poultry diet without deleterious effect on broilers. Keywords: Broilers, Acacia Seeds, Performance, Carcass Evaluation

Trypanosomiasis has been recognized as a scourge in sub-Saharan Africa for centuries and chemotherapy of the disease still remains unsatisfactory. This study is to explore an alternative source of antitrypanosomal agents from the stem bark of four Acacia species; Acacia nilotica, Acacia sieberiana, Acacia geradii and Acacia hockii. Dried stem bark of each plant was pulverized and extracted with 98% methanol by maceration. Phytochemical screening was carried out followed by in vitro testing of extracts on the motility of Trypanosoma congolense maintained in Ringer solution. Motility assessment of trypanosome was carried out after exposure with varied concentrations of the extracts for 2 hours. Thereafter, infectivity test was carried out using albino mice. Seventy-two mice, divided into twenty-four (24) groups of three animals were each inoculated with 100µl of the mixture containing the varying extract concentrations intraperitoneally. Berenil was used as standard drug control. Establishment of infection and subsequent Parasitaemiawere monitored in the animals for 60 days. The Phytochemical assay revealed the presence of anthraquinones, tannins, glycosides, cardiac glycosides and terpenes in all the extracts. Saponin was only present in Acacia nilotica and Acacia geradii. Incubation of parasites with each of the four acacia species recorded cessation in parasite motility which was concentration dependent. The highest concentration 20 mg/ml showed the highest effect within fifteen (15) minutes of incubation which was similar to the Berenil incubated control. However, lower doses (0.005 and 0.00005) mg/ml did not show difference from the non extract incubated negative control. Incubation of T. congolense with Acacia nilotica, Acacia sieberiana, Acacia geradii and Acacia hockii at 20, 10 and 1 mg/ml inhibited the ability of the parasites to establish infection in the albino mice as compared the standard control drug. The results indicate that the methanolic stem extracts of the four acacia species possess antitrypanosomal activity with potentials for the treatment of trypanosomiasis.

Pastoral nomadic communities of East Africa’s drylands are gradually shifting towards a sedentary type of production. However, successful animal production under such settings demands for integrated on-farm management of the various animal feed resources. The objective of this study was to characterize feed resources of goats in the pastoral area of Karamoja sub-region, a dry land area in northeastern Uganda. Structured interviews were conducted involving 300 randomly selected households. Results revealed seventy plant species distributed in 31 families were fed to goats. The species were dominated by browses (trees and shrubs) 54%; herbs 21%; grasses 19%; climbers and hedges 5%. Balanites aegyptica, Grewia similis, Acacia sieberiana, Acalypha fruticosa, Acacia albida and Cadaba farinosa were the most frequently mentioned browse species. Farmers also use these species for other purposes notably building, human and livestock medicine, fencing, firewood and as vegetables during the dry season. Browses were available throughout the year unlike grasses and crop residues that were available seasonally. Since browses were available throughout the year in addition to being multipurpose, it is recommended that current efforts to actualize a sedentary lifestyle among Karamoja pastoralists integrate the planting and management of the most reported browse species in this study.

During the dry season, most plants and grasses dry up and ruminants are left with fewer plants to graze on. The plants available during such periods have relatively lower moisture contents and higher antinutritional factors because of the dry nature of the soil and prevalent atmospheric conditions. Increased levels of antinutritional factors above acceptable values, could have a detrimental effect on the metabolic and health status of animals grazing on such plants. This research work sought to determine the phytochemicals present and the levels of some antrinutritional factors in plants (Acacia senegal, Parkia biglobosa, Anogeissus leiocarpus, Acacia sieberiana, Vitellaria paradoxum, Tamarindus indica, Ficus carica, Ziziphus spinachristi Dichrostachus cinerea, Ziziphus mucronata) commonly grazed upon by ruminants in this region, to educate farmers and policy makers on the safety of these plants for ruminant nutrition. The plants were collected and identified, while phytochemical and anti-nutritional profiles were analyzed using standard spectrophotometric procedures. Quantitative antinutritional factors analysis showed that the level of oxalate varied from 15 to 180 mg/100 g, phytic acid from 23.51 to 53.41 mg/100 g and tannins from 0.486 to 1.850 mg/100 g, which are within internationally accepted permissible limits. Results of qualitative phytochemical analysis showed that flavonoids, tannin, cardiac glycosides and steroids were present in all the plants, while anthraquinones were absent. The results suggest that the browse plants in this location contain anti-nutrients at relatively low levels which make these plants safe for ruminant consumption. Key words: Plants, antinutritional factors, phytochemicals, grazing ruminants

This study aims to determine the composition and thermal behavior of three acacia gums, namely, Acacia sieberiana, Acacia gerrardii, and Acacia tortilis (ATR) from Sudan. The results showed high percentages of carbon and oxygen and a low percentage of sulfur in all samples. Thermal behavior was studied using differential scanning calorimetry and thermal gravimetric analysis. Differential scanning calorimetry thermal profiles showed early intensive endothermic peak at temperature 100°C (peak temperature) associated with negative enthalpy and specific heat values, and intensive exothermic peak at temperature about 300°C (peak temperature) associated with positive specific heat and enthalpy values for all samples. Thermal gravimetric analysis curves showed three decomposition stages for both A. sieberiana and ATR gums and two decomposition stages for A. gerrardii; the major decomposition occurred at temperature around 280°C for all samples. The overall results of the present study reveal that all gum samples studied are thermally stable, and they possess the potential to be used as food modifiers.

Organic matter degradation of Acacia nilotica, Acacia sieberiana, Annana senegalensis, Balanites aegyptiaca, Cassia sieberiana, Combretum leati, Faidhebia albida, Maerua angolensis, Prosopis africana and Vitex doniana using two different techniques: (i) the in sacco nylon bag degradation and in vitro gas production techniques. Samples were incubated in sacco and in vitro for 24, 48, 72 and 96 h. In sacco and in vitro OM degradation kinetics were described using the equation Y=a+b(1-e -ct ). The dry matter (DM) and crude protein (CP) were relatively high ranging from 934.00 to 984.60 g Kg -1 DM and 122.50 to 174.80 g Kg -1 DM in Cassia sieberiana and Acacis nilotica had the highest value (216.60 and 910.30 g Kg -1 DM for as and organic matter (OM) The highest value for neutral detergent fibre (NDF) and acid detergent fibre (ADF) was observed in Vitex doniana. The acid detergent fibre was generally high ranging from 86.40 to 144.70 g Kg -1 DM. The OM disappearance increases with increasing incubation time in all the browse forages ranging from 28.56 in Balanites aegyptiaca at 24 h to 76.53 in Combretum leati at 96 h. The OM degradation constant (a, b, a+b, lag T and ED) were all significantly different (P

The variation among tree species in their sapling responses to disturbances such as fire, herbivory and grass competition results in different probabilities of recruitment into savanna communities. A sapling’s ability to persist under these disturbances depends on its investment in growth, defences and stored reserves, based on soil available nutrients. We examined the survival and investments in growth and defence of the saplings of four Acacia species, in the presence of competing grasses, under varying soil nutrient levels. We also have evaluated the effects of fire on these saplings. We performed the study in a greenhouse at the UKZN Botanical Garden, Pietermaritzburg, South Africa. Nutrients had no significant effect on the survival of tree saplings regardless of fire treatment. Only 22.5 % saplings survived after fire treatment compared with 84 % of control saplings. Acacia sieberiana showed the highest resprout survival, while A. karroo did not survive the fire. Growth in A. nigrescens increased only at intermediate levels (0.5N, 1N) of the fertiliser provided. Condensed tannins in A. karroo also decreased at an intermediate level (1N) of fertiliser. Resprouts grew faster in stem height than in diameter and did not invest in chemical defences. No treatment had an effect on the proportion of root and shoot dry biomass. In conclusion, African acacias are not dependent on soil nutrients for their survival and differ in their ability to resprout after fire. Intermediate levels of nutrient availability are beneficial to sapling development as opposed to zero and high nutrient levels, due to nutrient-grass dynamics. The benefits of post-fire grass removal and an increase in nutrients can be effectively utilised by only a few species of acacias.

An experiment was conducted to determine preference intake and relative palatability indices of Acacia karroo, Acacia nilotica, Acacia tortilis, Acacia sieberiana and Acacia rhemniana in sheep and goats using a completely randomized design. The size of Experimental Farm from which the browses were harvested was 1842.75 ha. The leaf samples were randomly collected from various young trees. The samples were analysed for proximate composition, measured for intake and relative palatability indices of sheep and goats. Dry matter (DM) content ranged from 917.4 to 936.8 g/kg DM and organic matter from 822.9 to 892.2 g/kg DM. All acacia species contained crude protein content (CP) of more than 7–17% required for grazing animals. The content of neutral detergent fibre (ADF) and acid detergent fibre ranged from 372.8 to 658.1 and 150.0 to 464.6 g/kg DM, respectively and were significantly (P < 0.05) different among the species. All of the acacia species had low levels (0–5.57 g/kg DM) of condensed tannins. The intakes of all feeds except A. karroo and A. rhemniana were high in both sheep and goats. The leaves from A. sieberiana had the highest palatability indice (Pi) while those of A.rhemniana had the lowest Pi in both sheep and goats. It was concluded that there was an effect of acacia species on intake and relative palatability indices. Species A. sieberiana, A. nilotica and A. tortilis have potential as livestock fodder, based on moderate to high CP value, low ADF, low tannins, high intake and relative palatability indices.

As with many grasslands globally, the Highveld grasslands of South Africa are tree-less, despite having a climate that can support tree growth. Models predict that fire maintains these grasslands. The question arises as to why fire-tolerant savanna trees do not survive in these ecosystems? Savanna tree survival in mesic areas is restricted by demographic bottlenecks, specifically limitations to sapling-escape from fire. It was hypothesised that ancient highly leached soils from grassland areas would prevent saplings from growing fast enough to escape the fire-trap. Growth rates of savanna tree seedlings (Acacia karroo Hayne and Acacia sieberiana Burtt Davy) were measured in a common garden experiment using soils from ten sites collected along a savanna-grassland continuum. Soils from grassland sites were relatively nutrient-poor compared to those from savannas with lower pH, and associated cations. A. sieberiana growth rates responded to pH and these nutrients, whereas A. karroo growth was less strongly linked to specific nutrients. Even so, both species accumulated more biomass when grown in soils from savanna sites compared to grassland sites. An exception was a low elevation low nutrient savanna site that resulted in poor growth, yet sustains high tree biomass in situ. Differences between growth in grassland and savanna soils were small. They may contribute to, but are unlikely to explain, the treeless nature of these grasslands.

Aims In spite of the importance of African acacias in vegetation succession and provision of goods and services, little is known about life-history variations within and among species. Much of the work done on African acacias has focused on seed predation and germination and seedling establishment, especially of Acacia tortilis, Acacia nilotica and Acacia karroo. The primary aim of the present work is to investigate differences in the demography of Acacia polyacantha and Acacia sieberiana and the relationship between life-history characteristics and population size. A secondary objective is to assess how fire, an important ecological factor in savanna vegetation, might modify the growth and demographic dynamics of the two acacias. Methods The study was conducted at the Makeni savanna plot in central Zambia, southern Africa. Seedling emergence from both non-scarified and scarified seeds sown at different times in the wet season and the fate and growth of seedlings and saplings were monitored over a period of 4 years. Annual growth of permanently marked sample trees in annually burnt and fire-protected blocks was recorded over a 6-year period (2002–08) in order to assess inter-specific differences and how fire modifies tree growth patterns. Censuses of natural saplings and trees were conducted periodically in sample blocks to determine recruitment into these life-history stages. Important findings Seedling emergence and sapling survival rates were much higher in A. sieberiana than in A. polyacantha. However, both seedling and sapling growth rates were higher inA.polyacantha than in A. sieberiana but tree growth rates were similar in the two species. Under fire protection tree growth was significantly influenced by tree size and year while under annual burning only tree size significantly affected tree growth. The dominance of A. sieberiana over A. polyacantha at the study site was attributed to higher seedling emergence rate, higher sapling survival rate and a large sapling bank that forms a reliable source of tree recruitment. The life-history stage characteristics of A. polyacantha suggest that this is an early successional species.

Dry and mature tree fruits are a potential source of protein for goats in the semi-arid areas of southern Africa, but their chemical composition and feeding value is largely unknown. This study presents the chemical composition and in vitro fermentation of indehiscent whole fruits and separated seed and hull fractions from Acacia nilotica, Acacia erubescens, Acacia sieberiana, Acacia erioloba, Piliostigma thonningii and Dichrostachys cinerea trees. Results indicate that the N contents of whole fruits ranged between 13.5 g/kg DM (A. nilotica) and 27.1 g/kg DM (A. erubescens). Seeds had a higher N content than hulls for all tree species. A. nilotica, D. cinerea and P. thonningii fruits had high levels of extractable phenolics (758, 458 and 299 g/kg DM, respectively). Soluble phenolics (SPh) and ytterbium precipitable phenolics (YbPh) levels were negatively correlated to in vitro gas production but positively correlated to in vitro organic matter degradability (iOMD). Partition factors for whole fruits at 48 h ranged between 3.6 mg/ml for A. erioloba and 7.8 mg/ml for A. nilotica. Seeds of A. erioloba, A. erubescens and P. thonningii were consistently fermented more efficiently throughout the incubation period compared to their whole fruits or hulls. Estimating in vitro degradability of phenolic-rich substrates through filtration procedures can give erroneous results due to the loss of soluble phenolics, which are not necessarily degradable. The feeding value of fruits from D. cinerea and A. nilotica tree species may be reduced due to the presence of high levels of phenolics.

The study aimed at determining the population status of the different Acacia tree species producing gum arabic in the undisturbed, grazed and cultivated habitats in the Karamoja region, Uganda. A total of 135 sample plots each measuring 20 × 20 m2 (0.04 ha) with each habitat having 45 plots were selected and established in the seven counties using a simple random sampling technique. The tree species present, their abundances and sizes were recorded. Twelve Acacia species were identified and a total of 5535 recorded in the sampled area. Out of these, five were gum-producing acacias. Acacia senegal dominated the acacias in all the seven counties and in all habitats of Karamoja with Acacia nilotica (72.3%), Acacia seyal (13.4%), Acacia sieberiana (4%) and Acacia gerrardii (2.6%). Non-gum-producing acacias constituted 7.19% of the total abundance. The tree densities increased with increase in tree size in the undisturbed and grazed habitats but decreased in the cultivated habitat. Most Acacia trees were of large size, an indication of old age and poor regeneration that could affect their future population status. It is recommended that further investigations be carried out into the causes of poor regeneration of Acacia species.

In the first of a two-phased study, changes in rumen pH and concentrations of VFA were evaluated on diets based on pasture straw (negative control) or straw supplemented with alfalfa (Alfalfa diet), pods of Acacia sieberiana (Sieberiana diet), Acacia nilotica (Nilotica diet) or Leucaena leucocephala (Leucaena diet) for South African Merino rams. In the second phase, the effects of the same diets on the degradation of extracted straw in nylon bags and activities of microbial enzymes were investigated. The pH and total concentration of VFAs in rumen fluid ranged from 6.2 to 6.5 and 30–53 mmol l −1 , while degradation of DM and NDF varied from 126 to 269 g kg −1 DM and 233–309 g kg −1 NDF, respectively, among diets. Variations in pH were not significant ( P >0.05), but diet influenced ( P

The host specificity, infection process and effectiveness of nodules produced by several African sinorhizobial strains on different Acacia and Prosopis species (Leguminosae, Mimosoideae) were studied. Sinorhizobium arboris strain HAMBI 1552T, S. kostiense strains HAMBI 1489T and HAMBI 1493, S. saheli strain HAMBI 1496 and S. terangae bv. acaciae strain ORS 1058 induced nitrogen fixing nodules on seedlings of the following African or Latin American species (marked with *): A. angustissima * , A. mellifera, A. nilotica, A. oerfota (synonym A. nubica), A. senegal, A. seyal, A. sieberiana, A. tortilis subsp. raddiana, P. chilensis * , P. cineraria, P. juliflora and P. pallida * . All strains increased plant yield significantly compared with uninoculated seedlings watered with nitrogen-free medium, but none appeared to be superior. The sinorhizobial strains were unable to effectively nodulate Sesbania rostrata (Papilionoideae). All roots had hairs, but particularly in the case of Acacia spp. they were often sparse. After inoculation root hairs were deformed and, in general, infection in Acacia spp. occurred through short root hairs and in Prosopis spp. through longer ones. After entry, the rhizobia filled infection pockets in the root hair, which later expanded into sac-like structures. When infection threads occurred, they usually started from sac-like structures. Elongation and ramification of the nodules indicated that Acacia spp. and Prosopis spp. have indeterminate nodules. A persistent apical meristem, which is the characteristic feature of the indeterminate nodule type, was much clearer in Prosopis spp. than in Acacia spp. Sinorhizobial strains formed tumour-like structures with undifferentiated cell tissue on the Australian acacia A. holosericea and ineffective, nodule-like structures on the African P. africana.

International audience; Woody plant encroachment in grasslands is a worldwide phenomenon. Despite many studies, the consequences of woody plant encroachment on sub-canopy vegetation and soil properties are still unclear. To better understand the impacts of trees on grassland properties we examined the following questions using a mountainous sub-tropical grassland of South Africa encroached by an indigenous tree, Acacia sieberiana as a case study: (1) Do trees increase sub-canopy herbaceous diversity, quality and biomass and soil nitrogen content? (2) Do large trees have a stronger effect than medium-sized trees on grass and soil properties? (3) Does the impact of trees change with the presence of livestock and position of trees in a catena? We studied grass and non-graminoid species diversity and biomass, grass quality and soil properties during the wet season of 2009. Nitrogen in grass leaves, soil cation exchange capacity and calcium and magnesium ion concentrations in the soil increased under tall Acacia versus open areas. Medium-sized Acacia decreased the gross energy content, digestibility and neutral detergent fibre of grasses but increased the species richness of non-graminoids. Tall and medium Acacia trees were associated with the presence of Senecio inaequidens, an indigenous species that is toxic to horses and cattle. The presence of livestock resulted in a decrease in herbaceous root biomass and an increase in soil carbon and leaf biomass of grass under Acacia. Tree position in the catena did not modify the impact of trees on the herbaceous layer and soil properties. For management of livestock we recommend retaining tall Acacia trees and partially removing medium-sized Acacia trees because the latter had negative effects on grass quality.

The effects of heat treatment and fire on seed germination of Acacia sieberiana D.C. and Acacia gerrardii Benth. were studied. Dry heat and fire were studied separately. Seeds treated with dry heat were set to germinate in petri-dishes under laboratory conditions. Other seeds were planted in plots at the Uganda Institute of Ecology, Mweya, which were then burnt, and subsequent seedling emergence was monitored. The effect of heat treatment on seed germination depended on heat intensity and duration of exposure. Higher intensities reduced the germination capacity of Acacia seeds. Short exposure of seeds stimulated germination but prolonged exposure rapidly reduced seed viability. A. sieberiana had a higher heat resistance than A. gerrardii. The survival and germination of seeds after fire increased with depth of burial and A. sieberiana survived better than A. gerrardii. The germinability of seeds of A. gerrardii was not significantly increased by fire.

Summary A study on seed predation by bruchid beetles was carried out to understand the interactions between seed beetles and Acacia seeds in Queen Elizabeth National Park, Uganda. The beetles encountered in seeds were carefully isolated, preserved, labelled and identified. Seed infestation was assessed using cutting tests. Four seed beetles, Enaretha castelnaudi, Tuberculobruchus natalensis and Bruchidius spp. were found in two large seeds of Acacia sieberiana, while Caryedon serratus and Bruchidius submaculatus were found in small seeds of Acacia gerrardii. The small seeded A. gerrardii had a higher rate of infestation than the large seeded A. sieberiana, in spite of the latter species having more seed predators than the former. The intensity of seed predation on A. sieberiana had negligible differences within and between study sites. The intensity of seed predation was only significant with A. gerrardii at Kayampara study site. The possible compensatory response by A. sieberiana to seed predation by beetles is possession of many large seeds with adequate resources to accommodate a guild of seed predators. This study indicated the potential of seed predation as a biological control tool against the spread of A. gerrardii. Resume On a mene une recherche sur l'infestation de semences par des coeopteres bruchides pour comprendre les interactions entre les coleopteres et les semences d' Acacia au Parc National Queen Elizabeth, en Ouganda. Les coleopteres trouves dans les semences ont ete soigneusement isoles, conserves, etiquetes et identifies. On a evalue l'infestation au moyen de tests de recoupement. Quatre coleopteres, Enartha castelnaudi, Tuberculobruchus natalensis et Bruchidius spp. furent trouves dans les grandes graines d' Acacia sieberiana, tandis que Caryedon serratus et Bruchidius submaculatusetaient trouves dans les petites graines d' Acacia gerrardii. Acacia gerrardii, qui a de plus petites semences, presentait un plus fort taux d'infestation que Acacia sieberiana qui en a des plus grosses, malgre le fait que ce dernier a de plus nombreux predateurs que le premier. L'intensite de la predation des semences d' Acacia sieberiana ne presentait que des differences negligeables entre les sites de recherches. L'intensite de la predation des semences d' A. gerrardii n'etait significative qu'a l'endroit nomme Kayampara. Il est possible que la reponse d' A. sieberianaa la predation par les coleopteres soit la possession de nombreuses grosses semences disposant des ressources necessaires pour faire face a des quantites de predateurs. Cette etude indiquait la possibilite que la predation au niveau des semences soit un moyen de controle biologique contre la dispersion d' A. gerrardii.

Although grazing livestock may have direct negative effects on woody species through herbivory and trampling, (heavy-)grazing is often associated with woody plant encroachment. Two main mechanisms can explain the positive effects of grazers on woody cover: (1) Grazers reduce the interspecific competition with trees and may reduce fuel load, and (2) gut passage through livestock increases seedling establishment by scarification (increased germination) and fertilization by dung (higher survival and growth of seedlings). We tested the effects of fire, grass, cattle ingestion (transit) and dung on germination, seedling height and survival as well as on recruitment of Acacia sieberiana in a sub-humid grassland of South Africa. About 8,000 seeds were planted in the field in a randomized block design. The removal of grass by grazing and/or fire had the most important effect on Acacia recruitment in savanna. Our findings highlight the hierarchy of the main factors affecting Acacia recruitment, which provides new insights to the understanding of woody plant encroachment.

Twenty yearling lambs of mixed breed were grouped according to initial liveweight (20 +/- 2.7 kg), and each group was offered one of 5 concentrate rations as a supplement to a low quality, dry season Andropogon gayanus hay. Voluntary food intake and liveweight change were monitored over a 56 day growth period, after which 5 of the lambs were transferred to metabolism crates, in which digestibility and nitrogen balance studies were carried out. Ground Acacia sieberiana pods were substituted for maize offal in the experimental diets A, B, C, D and E at 0%, 15%, 30%, 45% and 60% respectively. Mean group intakes and growth rates were (913, 964, 1020, 1128 and 1004 g conc. DM/day) and (111, 120, 149, 165 and 119 g liveweight gain/day) respectively. A decline in both intake and growth rate were recorded as the level of A. sieberiana was increased beyond 45% of the supplement. This corresponded to a daily dry matter intake of Acacia pods in excess of 500 g, or 43 g/kg W0.75. This decline may have been due to the toxic effects of the phenolic compounds present in Acacia. It appears that up to a certain critical level of intake, A. sieberiana is able to support growth rates equal to or better than those obtained when feeding maize offal to lambs. This makes A. sieberiana an attractive low cost alternative, supplementary feed during the dry season.

Forty Menz rams weighing 20 to 22 kg and aged 13 to 18 months were individually offered 1·0 kg/day chopped maize stover and one of five supplements over a 70-day growth trial followed by a 10-day metabolism trial. The amounts of supplement offered were designed to supply 4·4 g nitrogen per day and with stover, sufficient nutrients to allow growth rates of 50 g/day. The control supplement, 80 g dry matter (DM) per day extracted noug (Guizotia abyssinica) meal, was compared with 194 to 212 g DM per day of fruits (pods (carpels) with seeds) of Acacia tortilis, A. albida, A. nilotica and A. sieberiana. For the control and four Acacia supplements respectively, mean growth rates were 32, 32, 21, 16, 4 (s.e.6) g/day and mean stover intakes 483, 430, 401, 347, 320 (s.e. 74) g DM per day. The low growth rates and intakes with A. sieberiana and to a lesser extent A. nilotica were probably related to their content of phenolic compounds including insoluble proanthocyanidins which may have lowered the digestibility of neutral-detergent fibre and nitrogen. A. tortilis and A. albida would appear to be of comparable nutritive value to noug meal as supplements to maize stover. Unlike noug meal Acacia fruits are widely available in rural areas of Africa. Further research is required to identify other tree species suitable for use as supplements and how to overcome the anti-nutritional factors.

Intake, growth, digestibility and nitrogen (N) utilisation by sheep were investigated for seven experimental diets which consisted of teff straw (Eragrostis abyssinica) fed ad libitum with phyllodes of Acacia cyanophylla (Diet 10, fruits of Acacia sieberiana (Diet 2), leaves of Acacia seyal (Diet 3) and Sesbania sesban (Diet 4), vetch hay (Vicia dasycarpa) (Diet 5) and noug cake (Guizotia abyssinica) (Diet 6). Diet 7 included urea to provide an intake of 1% N. A. cyanophylla had a high fibre and lignin content due to a high level of proanthocyanidins (condensed tannins). The three acacias had the highest content of soluble phenolics and insoluble proanthocyanidins. S. sesban had the lowest content of fibre and polyphenols. Diets containing acacias had the highest levels of feed refusals and the lowest intake of teff straw. However, the intake of A. seyal increased over time. Sheep fed S. sesban had the highest intake of teff straw. The growth rate was highest for Diets 4 and 5, reflecting high intakes, while sheep eating Diet 1 lost weight. Growth rates for sheep fed A. seyal were similar to those of sheep fed S. sesban and vetch hay during the last 7 weeks of the growth trial after intake had increased. Digestibility of fibre was lowest for diets containing acacias. Proanthocyanidins in A. cyanophylla may have complexed protein in the digestive tract causing negative digestion coefficients for lignin and N insoluble in neutral detergent. The content of faecal N that was soluble in neutral detergent was highest for sheep fed A. seyal, indicating higher excretion of microbial and endogenous N in the faeces. Urinary N loss was lowest and faecal N loss was highest for diets containing acacias. N balance was positive for sheep fed all diets except A. cyanophylla. The N fraction in diets containing acacias was not nutritionally uniform because of the influence of polyphenols on protein digestion and metabolism.

Acacia trees form the third largest woody plant family in southern Africa and are an important ecological component of the bushveld vegetation that is prevalent in the Limpopo Province of South Africa. The purpose of the study was to determine types and amounts of tannins and also to evaluate the nutritive value of tree foliages, Acacia karroo, Acacia nilotica, Acacia tortilis, Acacia galpinii, Acacia sieberiana, Acacia hebeclada and Acacia rhemniana, grown in the Limpopo Province and also to determine types and amounts of tannins occurring in them. Young leaves with petioles from seven tree foliages were collected from five different trees per species at the University of the North (now University of Limpopo) in April 2003, in a completely randomized design. Packed volume ranged from 1.50 mL/g for A. karroo to 3.00 mL/g for A. hebeclada whilst water retention ranged from 3.71 g/g for A. galpinii to 4.98 g/g for A. sieberiana. These results suggest that all the tree leaves have a high intake potential. All the Acacia species had crude protein levels above 100 g/kg dry matter (DM), ranging from 103 g/kg DM for A. rhemniana to 183 g/kg DM for A. sieberiana. Crude protein levels of this magnitude in a diet are adequate to support the maintenance requirements of cattle, sheep and goats at low to medium production levels. The Acacias contained medium to high levels of neutral and acid detergent fibres with ranges of 488 to 622 and 415 to 545 g/kg DM, respectively. In vitro DM and organic matter degradabilities varied from 345 to 534 and 254 to 474 g/kg DM, respectively. Acacia hebeclada, A. sieberiana and A. galpinii contained traces of total phenolics whilst A. tortilis contained approximately 90 g/kg DM of total phenolics and A. karroo, A. nilotica and A. rhemniana contained intermediate concentrations. Extract condensed tannin (CT) content ranged from 1.1 g/kg in A. hebeclada to 80.7 g/kg in A. karroo. At level above 50 g/kg, CT tends to negatively affect intake and digestibility in ruminants. Consequently, reduced intakes of A. galpinii, A. karroo and A. tortilis could be expected because they contained CT values above 50 g/kg. Only A. nilotica showed a sharp curve in the potassium iodate test, reflecting its considerable content of hydrolysable tannins (HT). All the other species had flat curves reflecting low levels of HT in them. The results showed that all the species except for A. galpinii, A. karroo and A. tortilis are of good nutritive value and have a potential for integration into livestock feeding systems in the Limpopo Province. South African Journal of Animal Science Vol. 35(4) 2005: 221-228

Gums are widely used to support the pharmaceutical, brewery, food, cosmetics and adhesive industries. Their uses are mainly based on their physicochemical properties and their mucilage. These properties make them act as emulsifiers, suspenders, thickeners, stabilizers, binders, and lubricants. In spite of the tremendous quantities of gums used in industries in Ghana, the chemistry of the locally available gums are not known. The main commercial gums used in industry are from the Acacia senegal, an exotic species. Chemical properties of gums from selected Acacia species - A. Acacia polyacantha, A. sieberiana, and A. dudgeoni were studied. The local gums had acceptable levels of moisture content (which is not more than 15%), less than 1.0% insoluble matter, less than 5% total ash value, and acid insoluble ash. They dissolved in water and sodium hydroxide, but not in most organic solvent. They showed levorotary optical rotation in water, and maintained a relative stable pH with time. The gums did not contain any starch or tannins. It was confirmed from the sugar reactions that their sugar composition were Rhamnose, Arabinose, Galactose, and Glucuronic acid. The viscosities increased with concentration and decreased with time, rose with pH till a pH of about 5 and then fell as the pH increased from 6 to 14. The local gums can be used as suitable substitutes for the commercially imported ones. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 2 No. 1 (2000) pp. 71-79

Trees are often absent from Highveld grasslands that can support woody vegetation in the absence of fire. Numerous mechanisms have been proposed for the exclusion of trees from these areas, including anthropogenic causes, frost, fire, grass competition and impeded drainage. We hypothesised that a lack of nutrients in the Highveld soils limits tree seedling growth resulting in increased fire-sensitivity of the seedlings. Acacia karroo and Acacia sieberiana seedlings were grown in an irrigated pot experiment, in soils collected along an altitudinal gradient from savannas up into grasslands. Growth was recorded over 6 months. The higher altitude grassland soils were more nutrient poor than the savanna soils with pH and T-value strongly negatively correlated with altitude (r =0.94, pb0.01; and r=0.70, pb0.01 respectively). Plant growth was most strongly correlated with B and N (r=0.36, pb0.01; and r=0.28, pb0.01 respectively). Overall there was a negative correlation of plant growth with the altitude from which soils were collected (r=0.12, pb0.01). Seedlings grown in high-altitude grassland soils gained ca. 0.64 of the biomass of those grown on lowaltitude savanna soils.We estimated that this would equate to 1.52 years longer to reach fire-escape height. Although soil nutrients had a strong influence on sapling growth, climate related factors in combinationwith firemore generally explain the lack of trees in upland grasslands.

Summary Following the recent decline in browsing and grazing pressures and changed fire regimes in Queen Elizabeth National Park, Uganda, Acacia thickets have encroached on grassland habitats important for grazing mammals. The objective of this research was to test experimentally the effects of fire behaviour, using simulated and natural fuel loading conditions, on A. sieberiana seedling and sapling regeneration. A high fire intensity (3200 kW m-1) in natural fuels stimulated high seedling emergence (172 seedlings m-2) compared to 6 seedlings m-2 without fire. Also a highly significant linear regression was established between percentage top-kill of seedlings and fire intensities. High fire intensities during late dry season fires were more effective in controlling sapling height growth than early dry season fires of low intensities. A conceptual diagram was developed to show the major factors and possible pathways leading to successful invasion by A. sieberiana into grassland openings of the savanna.

KORDOFANI, M. & INGROUILLE, M., 1991. Patterns of morphological variation in the Acacia species (Mimosaceae) of northern Sudan. A numerical taxonomic review has been carried out on the morphology of northern Sudanese Acacia species. Fifty-one characters were scored from 12 species sampled at 12 sites. There is evidence of large scale population variation. Within a single site species are distinct but a comparison of plants between different sites may obscure species differences. Each species has a peculiar local variant in each sampled site, even when sites are separated by only a few kilometres. The possible significance of this pattern of variation is discussed. Species complexes are delineated and useful species diagnostics described.

The effect of applying vesicular-arbuscular mycorrhizal (VAM) fungi or chopped roots of native plants to a standard, non-sterile nursery soil was investigated in a tree nursery in Ethiopia. Acacia abyssinica and Acacia sieberiana were grown for 3 and 4 months, respectively, in five different soils: standard nursery soil, soil inoculated with a tropical or with a temperate isolate of the VAM fungus Glomus mosseae , and soil inoculated with chopped roots of native forest plants or of grasses. Inoculation with both kinds of native roots and with the tropical G. mosseae isolate increased the shoot dry weight of A. sieberiana significantly, by 48, 33 and 36%, respectively, compared with seedlings in the standard soil. Inoculation with native forest roots and the tropical G. mosseae increased the shoot dry weight of A. abyssinica by 23 and 38%. The temperate isolate of G. mosseae did not improve the growth of either acacia species significantly. Growth stimulation was accompanied by a significantly higher mycorrhizal colonization in all cases except one, whereas shoot phosphorus and magnesium uptakes were generally not significantly affected. The survival of the A. abyssinica seedlings 6 months after their transfer from the nursery to the field was enhanced by all inoculations, although significantly so only with the tropical VAM isolate. The root dry weight after 18 months in the field was also improved in this treatment. The results demonstrate that application of a simple inoculum consisting of chopped roots of native plants with naturally occuring VAM fungi can be equally effective in enhancing seedling growth in tree nurseries in the tropical region as the more elaborate use of pure cultures of VAM fungi, both when seedlings are amply watered and when they are drought-stressed.

Acacia trees comprise a principal component of the diet of many African browsers. The resultant browsing pressure has led to the evolution of both physical and chemical responses in Acacia trees. In an observational study, we investigated the physical and chemical defenses in Acacia sieberiana var. woodii in response to different intensities of giraffe herbivory. Trees with high browsing intensity had significantly longer spines, smaller leaves and higher total cyanide (prussic acid) concentrations than trees with low browsing intensity. No significant differences were present in the density of spines and leaves between high and low browsing intensity sites. Similarly, no significant differences were found in the concentrations of condensed tannins and total leaf nitrogen. However, comparisons with other Acacia species revealed that the sampled A. sieberiana trees had substantially higher condensed tannin concentrations than many other species. It therefore appears that condensed tannins may form a high constitutive, or fixed, defence in A. sieberiana in this population, while prussic acid and spine length (with a decrease in leaf size) form important inducible defences.African Journal of Range & Forage Science 2007, 24(3): 123–129

SUMMARY (1) The effects of natural and simulated fire on insect-infested seed germination, seedling emergence and on the viability of seed pools in the soil of Acacia sieberiana were investigated in a savanna in Queen Elizabeth National Park, Uganda. (2) There was a strong potential for the population of A. sieberiana plants to increase from the viable seed pool of about 800 seeds m-2. Seedling emergence was 167 seedlings m-2 after one fire. Seeds collected from the soil surface of burned areas produced significantly higher total germination rates (650%,) than those from unburned areas (10%/,) when tested in the laboratory. As expected, seeds located at shallow depths were stimulated to germinate more readily by fire then seeds located deeper in the soil. (3) The germination was significantly reduced by the high bruchid larvae (Bruchidius spp.) infestation. Bruchid larvae are more sensitive to fire than the seed embryo and, thus, the heat treatment indirectly leads to higher germination. (4) Regression equations were developed for predicting the mortality of seed and bruchid larvae under different fire intensities. (5) A conceptual diagram of germination success of A. sieberiana was developed.