Tree size and herbivory determine below-canopy grass quality and species composition in savannahs

Large single-standing trees are rapidly declining in savannahs, ecosystems supporting a high diversity of large herbivorous mammals. Savannah trees are important as they support both a unique flora and fauna. The herbaceous layer in particular responds to the structural and functional properties of a tree. As shrubland expands stem thickening occurs and large trees are replaced by smaller trees. Here we examine whether small trees are as effective in providing advantages for grasses growing beneath their crowns as large trees are. The role of herbivory in this positive tree-grass interaction is also investigated. We assessed soil and grass nutrient content, structural properties, and herbaceous species composition beneath trees of three size classes and under two grazing regimes in a South African savannah. We found that grass leaf content (N and P) beneath the crowns of particularly large (ca. 3. 5 m) and very large trees (ca. 9 m) was as much as 40% greater than the same grass species not growing under a tree canopy, whereas nutrient contents of grasses did not differ beneath small trees

The effect of intensive physical training on cardiac autonomic variability - factors that may influence the results

The study dealt with the influence of exercise on the autonomic nervous system (ANS) and with factors that may influence the results. ANS function was measured in 183 young, healthy participants, before and after a twelve week standardised, medium-to-high volume physical training programme, in a controlled environment. The effects of the training programme were assessed on resting ANS functioning, during standing and on the response to an orthostatic challenge. ANS function was assessed by means of heart rate variability (HRV) determination. HRV was quantified by three different analytical techniques, i.e., time domain analysis (RR, STDRR, RMSSD and pNN50), frequency domain analysis (LF,LFnu, HF, HFnu and LF/HF) and Poincaré plot analysis (SD1 and SD2). The influence of technical variations, such as variations in tachogram length and period of recording, as well as the influence of pre-intervention values of physiological variables, such as blood pressure, BMI, VO2 max and ANS functioning, on the response to the exercise intervention, were assessed. Results on the exercise intervention showed: Increased supine, as well as standing, parasympathetic cardiac control as indicated by time domain, frequency domain and Poincaré analyses. Decreased sympathetic control in the supine position and increased sympathetic control during rising and standing. Increased vagal withdrawal, as well as increased sympathetic control during the first phase of the orthostatic response to rising from the supine position. Only an exercise-induced increase in sympathetic control when the orthostatic response was measured as the difference between standing and supine. Results on exercise-induced changes in sympathetic and parasympathetic ANS control differ, depending on posture. It is suggested that the effects of an exercise intervention on sympathetic and parasympathetic ANS control of the heart should be assessed from measurements in the supine, in the standing, and in response to an orthostatic stressor. It is further suggested that information obtained during rising will give additional information on the response of the ANS. This study showed that technical as well as physiological variations may lead to differences in the outcome of HRV studies. Results from the technique evaluation showed that the length and period of tachogram recordings should be standardised, especially during an orthostatic challenge. Starting the recording too late will miss out on the initial response to a change in body position. Longer recording times will represent the mean of HRV values obtained during the orthostatic response and that obtained after stabilisation in the standing position. Investigations into the influence of pre-intervention physiological status on exercise-induced changes showed: Baseline ANS functioning is a significant contributor to variations in the ANS response to an exercise intervention. Pre-intervention values for physiological variables, such as blood pressure, BMI and VO2 max do not have a significant influence on the HRV response to exercise in young, healthy individuals of average fitness Regression analyses confirm the correlation results, i.e. that baseline ANS function is a significant predictor of the ANS response to exercise. However, regression results indicated that the combination of pre-intervention values for LFms2, HFms2, BMI, VO2 max, gender and blood pressure, contributes only between 12.83% and 29.82%, depending on the HRV variable, to the exercise induced changes in the autonomic nervous system. Thesis (PhD)--University of Pretoria, 2011.Physiologyunrestricte

Demarcation of potentially mineral-deficient areas in Central and Northern Namibia by means of natural classification systems

Mineral deficiencies that lead to production losses often occur concurrently with climatic and management changes. To diagnose these deficiencies in time to prevent production losses, long-term monitoring of mineral status is advisable. Different classification systems were examined to determine whether areas of possible mineral deficiencies could be identified, so that those which were promising could then be selected for further monitoring purposes. The classification systems addressed differences in soil, vegetation and geology, and were used to define the cattle-ranching areas in the central and northern districts of Namibia. Copper (Cu), iron (Fe), zinc (Zn), manganese (Mn) and cobalt (Co) concentrations were determined in cattle livers collected at abattoirs. Pooled faecal grab samples and milk samples were collected by farmers, and used to determine phosphorus (P) and calcium (Ca), and iodine (I) status, respectively. Areas of low P concentrations could be identified by all classification systems. The lowest P concentrations were recorded in samples from the Kalahari-sand area, whereas faecal samples collected from cattle on farms in the more arid areas, where the harder soils are mostly found, rarely showed low P concentrations. In the north of the country, low iodine levels were found in milk samples collected from cows grazing on farms in the northern Kalahari broad-leaved woodland. Areas supporting animals with marginal Cu status, could be effectively identified by the detailed soil-classification system of irrigation potential. Copper concentrations were lowest in areas of arid soils, but no indication of Co, Fe, Zn, or Mn deficiencies were found . For most minerals, the geological classification was the best single indicator of areas of lower concentrations. Significant monthly variation for all minerals could also be detected within the classification system . It is concluded that specific classification systems can be useful as indicators of areas with lower mineral concentrations or possible deficiencies.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat X Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Physical activity of children from a small rural town, South Africa

INTRODUCTION : Physical activity plays an integral role in the normal physical, mental, social and cognitive development of children. One of the main reasons for overweight children in low- and middle-income countries like South Africa is inactivity. This study’s aim was to describe the physical activity measured in boys and girls from section 21, quintile 5 pre-primary and primary schools in a small rural South African town and to compare it with recommended international physical activity levels. METHOD : Seventy-eight rural children, representing Caucasian and black African children, divided into three age groups, were issued a piezoelectric pedometer for seven complete days. Pedometer data obtained were total steps, aerobic steps, aerobic walking time, calories and distance. Steps per day were compared with international levels. Correlation statistics examined the association between physical activity and adiposity. RESULTS : Boys in the age groups 9–11 and 12–14 years are statistically more active than girls of the same age (p = 0.005 and 0.045 respectively). Although girls’ physical activity levels tend to decrease with age, their aerobic activity levels increase with age. This group of rural children’s physical activity levels are far lower than the recommended international normative levels. No correlation was found between physical activity and adiposity. CONCLUSION : The pedometer data indicated that gender and age influence the activity of children. This group of rural children’s physical activity is far less than international normative levels. Nine to 11-year-old boys are the most active boys, and girls of 12–14 years old are the most aerobic active girls in this study, therefore the authors concluded that, to increase physical activity, the age group 9–11 may be the ideal age to focus on for gender-specific intervention programmes.http://www.safpj.co.za/index.php/safpjhttp://www.tandfonline.com/oemdam2016Sports MedicineStatistic

Seasonal diet changes in elephant and impala in mopane woodland

Elephant and impala as intermediate feeders, having a mixed diet of grass and browse, respond to seasonal fluctuations of forage quality by changing their diet composition. We tested the hypotheses that (1) the decrease in forage quality is accompanied by a change in diet from more monocots in the wet season to more dicots in the dry season and that that change is more pronounced and faster in impala than in elephant; (2) mopane (Colophospermum mopane), the most abundant dicot species, is the most important species in the elephant diet in mopane woodland, whereas impala feed relatively less on mopane due to the high condensed tannin concentration; and (3) impala on nutrient-rich soils have a diet consisting of more grass and change later to diet of more browse than impala on nutrient-poor soils. The phosphorus content and in vitro digestibility of monocots decreased and the NDF content increased significantly towards the end of the wet season, whereas in dicots no significant trend could be detected. We argue that this decreasing monocot quality caused elephant and impala to consume more dicots in the dry season. Elephant changed their diet gradually over a 16-week period from 70% to 25% monocots, whereas impala changed diets rapidly (2-4 weeks) from 95% to 70% monocots. For both elephants and impala, there was a positive correlation between percentage of monocots and dicots in the diet and the in vitro digestibility of these forage items. Mopane was the most important dicot species in the elephant diet and its contribution to the diet increased significantly in the dry season, whereas impala selected other dicot species. On nutrient-rich gabbroic soils, impala ate significantly more monocots than impala from nutrient-poor granitic soils, which was related to the higher in vitro digestibility of the monocots on gabbroic soil. Digestibility of food items appears to be an important determinant of diet change from the wet to the dry season in impala and elephants

Revisiting the importance of childhood activity

Formalised exercise programmes for children and adolescents are becoming increasingly important. There has been a drastic increase in documented childhood morbidity and mortality relating to poor nutrition and low activity levels in recent years. Regular physical activity decreases the risk of chronic disease and is also a fundamental component in the management of illnesses. Recommendations for the paediatric population remain insufficient and ill-defined. This article revisits the risks of physical inactivity in childhood and provides the latest recommendations for exercise prescription in the paediatric population. Inactive children have a higher risk of developing chronic diseases, such as obesity, type 2 diabetes, high blood cholesterol and hypertension. Other undesirable consequences include orthopaedic problems, cardiovascular disease and various psychological complications. Both aerobic and resistance training should be incorporated into paediatric exercise programmes. The recommended guidelines for childhood activity are 60 minutes of moderate-intensity exercise every day of the week. This article highlights the importance of formalised paediatric exercise programmes in disease prevention and health promotion. A healthy and happy adolescent population ultimately contributes to an adult population with a low risk of ill health.http://www.safpj.co.zaam201

Herbaceous forage and selection patterns by ungulates across varying herbivore assemblages in a South African savanna

Herbivores generally have strong structural and compositional effects on vegetation, which in turn determines the plant forage species available. We investigated how selected large mammalian herbivore assemblages use and alter herbaceous vegetation structure and composition in a southern African savanna in and adjacent to the Kruger National Park, South Africa. We compared mixed and mono-specific herbivore assemblages of varying density and investigated similarities in vegetation patterns under wildlife and livestock herbivory. Grass species composition differed significantly, standing biomass and grass height were almost twice as high at sites of low density compared to high density mixed wildlife species. Selection of various grass species by herbivores was positively correlated with greenness, nutrient content and palatability. Nutrient-rich Urochloa mosambicensis Hack. and Panicum maximum Jacq. grasses were preferred forage species, which significantly differed in abundance across sites of varying grazing pressure. Green grasses growing beneath trees were grazed more frequently than dry grasses growing in the open. Our results indicate that grazing herbivores appear to base their grass species preferences on nutrient content cues and that a characteristic grass species abundance and herb layer structure can be matched with mammalian herbivory types

The usefulness of faecal phosphorus and nitrogen in interpreting differences in live-mass gain and the response to P supplementation in grazing cattle in arid regions

The average daily gains of heifers and oxen on commercial and experimental farms in Namibia were used to indicate production differences in several areas and at different rates of phosphorus and protein supplementation. Faecal concentrations of phosphorus and nitrogen were used to indicate concentrations of these nutrients in grazing. Areas with high concentrations of nitrogen in faeces proved to support high levels of average daily gain. Animals responded positively to phosphorus supplementation only when faecal nitrogen concentrations were above 12 g/kg DM. Nitrogen concentrations in faeces were directly related to average daily gain of heifers, but protein supplementation did not have a significantly positive effect on average daily gain.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat X Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Investigation of the knowledge of South African high school rugby coaches on concussion and the return-to-play protocol

BACKGROUND: Coaches are pivotal in the management of concussed players. Assessing the knowledge of high school rugby coaches with regard to concussion management will enable relevant future education on this topic to be covered. OBJECTIVES: To investigate the knowledge of South African high school rugby coaches on concussion symptom recognition, knowledge and stepwise return-to-play (RTP) protocols. METHODS: A cross-sectional descriptive study involving 143 first team, high school rugby coaches was completed via an electronic questionnaire. Independent variables included coach demographics, qualifications, experience, BokSmart accreditation, and school size. Dependent variables included knowledge scores on concussion symptoms, general concussion knowledge, stepwise RTP and Maddocks questions. Relationships between total scores for different demographic groupings were established using non-parametric techniques. RESULTS: The coaches had high general, symptom and overall concussion knowledge scores (77% - 80%) in contrast with low RTP scores (62%) and very low Maddocks questions knowledge scores (26%). The 35-44-year age group received top scores for symptom recognition (p=0.034) and total concussion knowledge (p=0.041). Larger category school coaches (p=0.008) and BokSmart accredited coaches (p=0.041) outperformed all other coaches in general concussion knowledge and total knowledge, respectively. However, respondents were not familiar with emotional symptoms or the importance of cognitive rest after a concussion. Educational programmes were the most popular knowledge source for coaches. CONCLUSION: In general, coaches presented with good general concussion knowledge but lesser expertise on emotional symptoms, cognitive rest and RTP management. Modifiable predictors of knowledge included the expansion of BokSmart accreditation, focussing information sessions on smaller rugby size schools and the education of coaches younger than 35 years or older than 45 years of agehttps://journals.assaf.org.za/index.php/sajsmdm2022Sports Medicin

Acute corticosteroid-induced rhabdomyolysis in a golf player

Acute corticosteroid-induced rhabdomyolysis is a rare, but potentially life-threatening, condition that deserves the attention of medical professionals and sport scientists. Early diagnosis is vital in minimising the secondary damage caused by rhabdomyolysis. This case of rhabdomyolysis highlights the severity of symptoms and the importance of decisive treatment. Clinicians should be familiar with the most common symptoms of acute corticosteroid-induced rhabdomyolysis to enable early diagnosis and efficient management of this condition.http://www.journals.co.za/sama/m_sajsm.htmlam2013ay201