Veld condition in the south‐eastern Transvaal and its effect on grazing capacity

Abstract

A survey conducted on sites throughout the south‐eastern Transvaal, representing 1,4 million hectares of natural veld has confirmed the parlous state of composition, cover and vigour. The implications which these conditions hold, not only for conservation of soil and water resources, but also for the livestock industry in this area, with specific reference to the current grazing capacity of the veld, are discussed.     

Relations between soil factors and herbage yields of natural grassland on sandy soils in the south‐eastern Transvaal

Forty systematically‐placed observation points were established in a 1.5‐ha area of floristically unifoim veld in which productivity varied spatially. At each point grass yields were determined by harvesting quadrats at eight‐week intervals during the growing season, and the volumetric water content of the soil was measured weekly. In addition, root mass and root‐N content, and soil variables involving C and N contents, extractable P, K, Ca and Mg, cation exchange capacity and base saturation, pH, clay content and soil depth, were determined. The data were examined using linear correlations between variables, principal components analysis and multiple regression. The major factors associated with variations in yield were, in order of importance, soil water content, the N supply (as expressed by root‐N content or root‐N mass) and the cation supply (as expressed by the topsoil variables, extractable Ca or cation exchange capacity or percentage base saturation). There was a relatively weak positive association between yields and the H⁺ concentration in the subsoil, and a weak negative association between yields and the clay content of the topsoil. A multiple regression function involving all five factors accounted for 77.3% of the variation in dry matter yield.     

A critical analysis of veld management recommendations for sourveld in the south‐eastern Transvaal

Surveys have shown that the grazing value of veld in the south‐eastern Transvaal is well below the estimated potential. Extension efforts aimed at rectifying the situation have been unsuccessful in that most recommendations have not been acceptable to producers. An appraisal of the factual base for the recommendations revealed that the latter are seriously flawed. Although enough is known for the formulation of greatly improved recommendations, there is a need for critical research to broaden the factual base. Aspects requiring special attention are indicated.     

Exploratory trials on reinforcement of veld with legumes in the south‐eastern transvaal highveld

Abstract

The feasibility and potential of reinforcing veld with legumes in the south‐eastern Transvaal highveld was assessed in a number of trials during the period 1974–84. Experience was gained with regard to methods of establishment, adaptation of legumes to the local environment, responses to fertilization, especially with lime and superphosphate, and the reaction of legumes to fire and grazing. In all, 17 legumes were involved, including the genera Coronilla, Desmodium, Glycine, Lespedeza, Lotus, Macroptilium, Medicago, Neoto‐nonia, Trifolium and Vigna. Only Coronilla varia (crownvetch) showed a satisfactory degree of persistence. However, crownvetch is slow to establish, is intolerant of waterlogging and has a relatively high requirement for lime and phosphate. Considering these features, and the probability of undesirable changes in grass species composition in reinforced veld, it is recommended that intensification be achieved through development of improved pastures for use in conjunction with veld, rather than by means of veld reinforcement.     

Determinants of herbaceous plant species composition on a number of ranches in the north‐western Transvaal

Herbaceous plant species composition was measured on ranches in the Thabazimbi district, Transvaal, to obtain veld composition scores and to quantify the relations between such scores and certain determinants considered important in influencing species composition. Determinants investigated were mean annual rainfall and herbivory (stocking rate). The survey was undertaken on seven game and cattle ranches in Combretum apiculatum woodland of the Mixed Bushveld (Acocks 18) of the north‐western Transvaal. Rainfall for the season preceding the vegetation survey and bulk and selective grazer stocking rates had a significant effect on veld composition scores. The recommended agricultural grazer stocking rate for the survey area is 12.5 LSU 100 ha"¹ a"¹. Under the present conditions and in view of the findings of this survey, it is suggested that a grazer stocking rate of 6.25 LSU 100 ha^?1 a^?1 be implemented.     

The quality of herbage ingested by cattle in rotationally grazed semi‐arid grassveld of the eastern Cape

Oesophageal fistulated steers were used to sample herbage daily during periods of occupation on veld in good and moderate condition. Forage quality was assessed in terms of in vitro dry matter digestibility and digestible crude protein. The quality of herbage ingested remained fairly constant as forage availability declined during periods of occupation, even when swards were grazed very severely. Digestibility declined somewhat from spring through to winter, but digestible crude protein content in the diet was unaffected by time of year. The quality of forage ingested during winter was nevertheless still high, even after a full growing season's rest. It was sufficient for growing steers to gain 0,75 kg livemass per day. Trends were similar on both veld condition types. It was concluded that, in semi‐arid grassveld of the eastern Cape, forage availability is likely to have a greater influence on animal performance than forage quality.     

Interactions of grazing and rainfall on vegetation at Grootfontein in the eastern Karoo§

Rainfall and grazing are primary drivers of vegetation composition in the Nama-Karoo. Increased rainfall increases grassiness, to where Nama-Karoo transitions to grassland. Severe grazing treatments (e.g. continuous or summer-only) increase abundance of grazing-tolerant dwarf shrubs and annual grasses, and decrease perennial grasses. Grootfontein, which is ecotonal between the Nama-Karoo and Grassland Biomes, houses long-term grazing trials. The area has experienced higher-than-average rainfall in recent decades. Plant basal cover data from the 1960s and 2010s allow several hypotheses to be addressed: (1) historical severe grazing (until 1985) will limit subsequent grassiness (grazing legacy effect); (2) severe grazing will preclude increases in grassiness, independent of rainfall (herbivore trap effect); and (3) historically leniently-grazed sites will transition to grassland with increased rainfall (biome shift effect). Rainfall was lower from 1957–1966 (350 mm) than from 2003–2012 (490 mm). The grazing legacy effect was supported based on the abundance of Aristida diffusa, despite all sites becoming much grassier. The herbivore trap effect was not supported. The biome shift effect was supported in that shifts to grassland sometimes occurred. Results suggest that increasing rainfall has prompted a shift to much increased grassiness and decreased abundance of dwarf shrubs, and that grazing had a smaller secondary effect.     

A preliminary investigation of area‐selective grazing in the Southern Tall Grassveld of Natal

The consequences of area‐selective grazing by cattle under three stocking rates and at two sites in the Southern Tall Grassveld of Natal were investigated. Soil compaction was found to significantly distinguish area‐selected patches from non‐selected veld (P≤0.01), while non‐significant differences in soil nutrient and moisture status were recorded. Area‐selected and non‐selected patches may be distinguished on the basis of species composition. Area‐selected patches are characterized by Aristida congesta subsp. barbicollis, Microchloa caffra and Eragrostis racemosa. Non‐selected veld is characterized by Themeda iriandra, Tristachya leucothrix and Hyparrhenia hirta.     

Grass species composition,yield and quality under and outside tree crowns in a semi‐arid rangeland in south‐western Zimbabwe

Abstract

A two‐year study was conducted in lightly grazed areas of Matopos Research Station, Zimbabwe, to evaluate the impact of widely spaced trees on understorey grass composition, yield and quality. The study trees were Terminalia sericea and Acacia karroo. Ordination techniques using grass density and biomass as indices separated quadrats according to soil type but not grass species according to understorey or open areas or according to tree species. Grass yield under tree crowns was similar to open areas, in contrast with most reports where understorey areas had higher yields. The high understorey grass quality that has been reported from savanna areas exhibiting grass composition differences was not expressed. Selective grazing of palatable perennial grasses growing in association with tree crowns and their eventual replacement by low‐yielding and less‐palatable grasses that normally grow in open areas is proposed as an explanation of the unique tree‐grass interaction scenario of this study. In areas where this replacement has occurred, recovery may require management interventions.     

Biology and pathology of the intestinal M‐cell. A review

Summary

The literature of the intestinal M‐cell, which is part of the epithelium covering the gut‐associated lymphoid tissue (GALT), is reviewed. Attention is paid to the localization, structure, origin and function of this cell, under both normal and pathological conditions.     

Classification of the grass layer of semi‐arid rangeland in the Smaldeel area of the eastern Cape

Abstract

Hierarchical classification based on proportional species composition of the grass layer was used to identify and classify semi‐arid rangeland into range types. The relation between range types produced by the classification and the environmental parameters measured were investigated using a two‐group, and a multi‐group stepwise linear discriminant function analysis. The first split of the TWINSPAN dendrogram separated savanna from open grassveld. The open grassveld was characterized by Themeda triandra, Microchloa caffra, Eragrostis capensis and E. plana and the savanna by Setaria neglecta, Sporobolus fimbri atus,Panicum stapfianum and Cymbopogon plurinodis. The two range types were best discriminated by rainfall, soil depth and altitude with sites in the grassveld corresponding to deep soils and receiving rainfall of more than 450 mm a^‐1, and sites in savanna corresponding to shallow soils and receiving rainfall of 400–500 mm a^‐1. Further divisions within these two range types were related to soil textural and chemical characteristics of the A‐horizon. Multi‐group discriminant function analysis identified eight environmental variables which best discriminate between range types at level 3 of the hierarchical dendrogram. Rainfall, soil depth and altitude were selected as the most important environmental variables discriminating between range types. Reclassification by discriminant analysis using the eight selected environmental factors resulted in a 67% concurrence with range types. It is proposed that the area be stratified on the basis of the current classification for monitoring and management purposes.     

Seasonal grazing capacity of an irrigated grass/legume pasture in the Rûens area of the southern Cape

Seasonal changes in grazing capacity of an irrigated grass/legume mixture consisting of lucerne, red clover, white clover, tall fescue, cocksfoot and perennial ryegrass were determined in the Rûens area of the southern Cape. Applying variable stocking rates and three grazing pressures (1,5; 2,25 and 3,0 kg DM/dry sheep‐unit/ day) in a six‐paddock grazing system, it was found that the mean annual stocking rate for maximum wool yield was 54,4 dry sheep‐units/ha over a period of three years. The seasonal grazing capacity of the pasture varied throughout the year and dry matter availability was most limiting during winter and highest during spring. The clover component of the pasture was depressed by the high grazing pressure and declined with age, while the grass content increased proportionally. The proportional lucerne content of the pasture material was more stable and was promoted by the high grazing pressure, but was not influenced by increased pasture age.     

Short‐term effects of cattle‐to‐sheep ratio and stocking rate on patch grazing in sour grassveld

Abstract

The short‐term effects of stocking rate (AUE ha^?1) and cattle‐to‐sheep ratio on the extent and severity of patch grazing and on patch size were evaluated. The extent of patch grazing was proportional to stocking rate, and livestock species had a small but significant effect. Patch size was also a function of stocking rate. Cattle and sheep had similar effects on patch size distribution when stocked at the same number of AUE ha^?1. The severity of grazing within a patch was influenced by both stocking rate and cattle‐to‐sheep ratio. Recommendations that cattle should be grazed together with sheep and that cattle should be in greater proportion (in terms of AUE ha^?1) than sheep, which are aimed at limiting the severity of grazing by sheep, are supported. However, severe grazing within patches is an inevitable consequence of sheep grazing irrespective of the stocking rate or cattle‐to‐sheep ratio applied.     

Modification of soil nutrients and micro‐climate by tree crowns in a semi‐arid rangeland of south‐western Zimbabwe

Abstract

Tree crowns in semi‐arid areas have often been found to create micro‐habitats of improved soil physical and nutrient status and reduced evapotranspiration. These encourage the growth of mesic, palatable and high yielding perennial grasses in otherwise arid environments. A two‐year study, in areas with a long history of light grazing, at Matopos Research Station sought to establish whether the soil nutrient status and micro‐climate under tree crowns are different from those in open areas, and whether the differences are affected by soil type and tree species. The study trees were Terminalia sericea and Acacia karroo. There were consistent patterns in soil nutrient status between understorey and open areas, although these patterns were largely not significant. There was also a consistent pattern in soil volumetric water content of open areas > T. sericea > A. karroo understorey areas. Tree crowns reduced solar radiation reaching understorey areas by an average of 88% and rainfall by an average of 15%. The findings on soil nutrient status are consistent with results from disturbed systems, and challenge the dogma, at least for soil nutrient status, that conservative stocking rates are beneficial.     

Chemical composition and nutritional value in vitro of mechanically‐deboned poultry meat

1. The composition by proximate analysis, amino acid content and digestibility by mammalian proteolytic enzymes of pastes from mechanically‐deboned chicken breasts wings, necks and backs, and hand‐deboned breast were measured. Values obtained were used to calculate indices of nutritional value.

2. All pastes compared favourably with similar protein materials used for human food. Mechanical deboning did not alter the nutritional indices.

3. The protein quality and digestibility of the breast were somewhat higher than those for other parts.     

The effect of rotational grazing for periods of one or two weeks on the build‐up of lungworm and gastrointestinal nematode infections in calves

Summary

An experiment was carried out with three groups of grazing calves and one housed control group to study the effect of rotational grazing for periods of 1 and 2 weeks on the build up of lungworm and gastro‐intestinal nematode infections respectively. The experiment demonstrated that rotational grazing for periods of I week on six plots prevented the build‐up of heavy lungworm infections. A buildup of heavier lungworm infections was observed in a group that was rotationally grazed for periods of 2 weeks on three plots and a group which remained on one plot throughout the grazing season; there was no difference between these two groups. In all three situations, there was an adequate development of immunity against D. viviparus, as measured by worm recovery after challenge infection at the end of the experiment in comparison with worm recovery of the similarly challenged control group. Neither rotational grazing scheme protected the calves against gastrointestinal helminthiasis, because tracer calves, which grazed for 4 days only in August or October, acquired infections which would have resulted in severe illness or even death if necropsy had been postponed for a week.     

A survey of the prevalence of blowfly strike and the control measures used in the Rûens area of the Western Cape Province of South Africa

Blowfly strike and the methods used to combat blowfly strike were recorded on 33 properties in the R?ens area of South Africa during 2003/2004. Data were recorded on Merino and Dohne Merino hoggets (n = 4951) with at least 3 months' wool growth. The following data were captured: presence or absence of strike, site of the strike (body or breech), presence or absence of dermatophilosis as well as subjective scores for wool quality and wool colour. Control measures recorded include: chemical treatment (preventative and spot treatment), crutching, mulesing and the use of the Lucitrap system. Blowfly strike was not significantly influenced by gender or breed. Hoggets suffering from dermatophilosis were more likely to be struck, compared with contemporaries not suffering from the skin disorder (0.057 vs 0.027; P < 0.05). Merino hoggets generally had higher scores than their Dohne Merino contemporaries for wool quality (32.6 vs 27.4; P < 0.05) and wool colour (29.0 vs 27.2; P < 0.05). There was an indication that the Lucitrap system may have reduced flystrike, but the effect was not statistically significant (P = 0.19 for overall strikes and P = 0.12 for body strike). The Mules operation benefited overall flystrike (0.013 vs 0.110; P < 0.05); mainly through an effect on breech strike (0.010 vs 0.109; P < 0.05). The proportion of fly strikes increased with wool length, and declined with an increase in farm size in wool colour score. None of the ethically acceptable control measures assessed could substantially reduce blowfly strike on their own, and an integrated pest management programme was proposed.     

A preliminary assessment of association‐analysis in the Kroonstad area

Vegetation in the Kroonstad area was sampled by means of a stratified random distribution of 235 4mx4m quadrats within physiographic‐physiognomic categories as determined and delineated on aerial photographs. “Normal” and “inverse” association‐analyses were carried out “Normal” association‐analysis where low‐frequency species were, respectively, included in and excluded from the computation, gave broadly similar results in so far as the major groupings are concerned. Local frequency and constancy estimates were computed for various groupings. Association tables were drawn up for major groupings and Poore's “successive approximation” approach was adopted in reducing species associations to noda. There is a strong subjective element in this determination of noda, and an effort should be made to reduce it to a minimum.     

Serological and parasitological survey of dourine in the Arsi–Bale highlands of Ethiopia

This study was conducted from August 2005 to January 2007 to determine prevalence and distribution of dourine in horses and to investigate the occurrence of clinical and carrier cases in donkeys and mules in the Arsi–Bale highlands. Study methodology was based on questionnaire, serological, clinical and parasitological survey. The questionnaire indicated that dourine is a major health problem of equines in the Arsi–Bale highlands. Though dourine is commonly observed throughout the year, it has a seasonal character and occurs mostly during the breeding season from June to late September. Serological screening of 646 horses showed a seroprevalence of 184 (28%), 161 (25%) and 125 (19%) for card agglutination test for trypanosomosis, LATEX and enzyme-linked immunosorbent assay, respectively. Risk factors were parity number, previous history of abortion and body condition score. No trypanosomes could be detected by Giemsa staining or by haematocrit centrifugation technique. Ten puppies inoculated with blood samples, genital washes and oedematous fluids remained parasitologically negative. Different characteristic signs of dourine were observed. During the genital stage, mares showed vaginal oedema, discharge and presence of depigmented scars over the external genitalia. In stallions, oedema of the scrotum and prepuce, prepucial and urethral discharge, and ulceration of the genital mucosae mainly of the penile were observed. In both sexes, lameness in one or both legs, partial dragging and stiffness of the hind legs and incoordination were the dominant signs observed as nervous form of the disease.     

A survey of eastern equine encephalomyelitis in Florida horses: Prevalence,economic impact,and management practices, 1982–1983

In spite of the availability of vaccines, eastern equine encephalomyelitis (EEE) virus continues to cause significant death losses in Florida horses. Veterinarians engaged in equine practice in Florida were surveyed regarding their experiences with EEE, and their responses were compared with serologic data available from the State of Florida Animal Disease Diagnostic Laboratory for 1982 and 1983. On the assumption that most cases of encephalitis in Florida are caused by EEE virus, considerable under-reporting was apparent. Clinical cases of EEE were comfirmed in every month of the year with the highest incidence observed in June and July. Northern and central Florida had the highest number of cases reported. Most deaths (78%) occurred in unvaccinated animals, indicating that greater horse owner awareness is needed. Deaths in vaccinated animals raised questions of the efficacy of current vaccines or their schedule of administration particularly in young horses. Vaccination schedule recommendations were variable between veterinarians with regard to annual versus semiannual EEE vaccination and age of first vaccination for foals. A conservative estimate of the cost to EEE to the state equine industry was greater than $1 000 000 per year.