The seasonal incidence of helminth parasites and of Oestrus ovis in Karakul sheep in the Kalahari region of South West Africa/Namibia.

The seasonal incidence of gastro-intestinal helminths and of Oestrus ovis was determined by slaughter of successive groups of 4 tracer lambs, each exposed on pasture for 33 days. Haemonchus contortus was present from March 1979 to early July 1979, with a generally increasing percentage of 4th stage larvae in each successive month. A "spring rise" in the egg count was seen in flock sheep in October 1978. Oesophagostomum columbianum was recovered from tracers slaughtered in March 1979. Apart from December and March, Moniezia spp. were present from November 1978 to early July 1979. Oestrus ovis was active from September 1978 to early June 1979, with peak larval burdens recorded from October to December and from April to early June.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Attempts to transmit Anaplasma marginale with Hippobosca rufipes and Stomoxys calcitrans

Three attempts to transmit anaplasmosis with field collections of Hippobosca rufipes were unsuccessful, despite the fact that the flies had been fed initially on splenectomized cattle acutely infected with Anaplasma marginale. However, 1 out of the 3 attempts, made concurrently with the others, to transmit this organism with Stomoxys calcitrans was successful. The prepatent period was 27 days.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format

Arthropod parasites of Hartmann's mountain zebra, Equus zebra hartmannae, in South West Africa/Namibia

Twelve Hartmann's mountain zebra, Equus zebra hartmannae, were shot for arthropod parasite recovery during the period June 1980-June 1981 on a farm in the Khomas Hochland region of South West Africa/Namibia. Four species of Gasterophilus larvae, 1 species of Rhinoestrus larvae and 3 ixodid tick species were recovered. The seasonal prevalence of the Gasterophilus species larvae and of Rhipicephalus evertsi mimeticus was determined. Three horses examined on the same farm were infested with larvae of 2 Gasterophilus species and with the same ixodid tick species as the zebras.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.University of Pretoria. Council for Scientific and Industrial Research.am201

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

Studies on the parasites of zebras. III. Nematodes of the mountain zebra from the farm "Kelpie" and the Namib-Naukluft Park, South West Africa/Namibia

Twelve mountain zebra which were culled at monthly intervals on the farm "Kelpie" in South West Africa/Namibia were examined for helminths. The zebras varied in age from 2-15 years, the middle group of which, aged 4-7 years, had the highest worm burdens. Fourteen species of nematodes belonging to the families Atractidae, Strongylidae, Oxyuridae, Setariidae and Spiruridae were recovered. The highest worm burdens were those of Crossocephalus sp. with 692-61 066 680 and Probstmayria vivipara with 1 257 810-42 004 300. The predominance of the atractids is discussed. The nematodes consistently present were: Cylicodontophorus n. sp. (44-2 107), Triodontophorus spp. (2-934), Cylindropharynx spp. (20-2 332), Crossocephalus sp. and P. vivipara. Two new species, Cylicostephanus longiconus and Cylicodontophorus n. sp., were reported. An additional 3 mountain zebra, culled in the Namib-Naukluft Park, were also examined for helminths. Of 3 zebras ranging in age from 2- 7 years, the 2 older animals had the highest helminth burden. Ten species of the nematodes belonging to the same families mentioned above were recovered. The only Spiruridae present were 3 Habronema majus in 1 zebra. The highest worm burdens were those of Crossocephalus sp. With 64 052-883 070 and P. vivipara with 50 720-220 200. The nematodes consistently present were the same as those in the "Kelpie" zebra. In addition, a 2nd, new species of Cylicodontophorus was reportedThe articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.Council for Scientific and Industrial Research. University of Pretoria

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

The prevalence of helminth and arthropod parasites of warthog, Phacochoerus aethiopicus, in South West Africa/Namibia

A total of 38 warthog, Phacochoerus aethiopicus, shot on a farm in northern South West Africa/Namibia were examined for internal and external parasites at monthly intervals over a period of 13 months. They harboured cestodes, 9 nematode species, 6 ixodid tick species and 1 species each of an argasid tick, a flea, a louse and larvae of a dipteran fly. Clear patterns of seasonal abundance could be determined only for the spirurid stomach worm, Physocephalus sexalatus, and the sucking louse, Haematopinus phachoeri.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.University of Pretoria

First-principles study of the structural energetics of PdTi and PtTi

The structural energetics of PdTi and PtTi have been studied using first-principles density-functional theory with pseudopotentials and a plane-wave basis. We predict that in both materials, the experimentally reported orthorhombic $B19$ phase will undergo a low-temperature phase transition to a monoclinic $B19'$ ground state. Within a soft-mode framework, we relate the $B19$ structure to the cubic $B2$ structure, observed at high temperature, and the $B19'$ structure to $B19$ via phonon modes strongly coupled to strain. In contrast to NiTi, the $B19$ structure is extremely close to hcp. We draw on the analogy to the bcc-hcp transition to suggest likely transition mechanisms in the present case.Comment: 8 pages 5 figure

Long-term effects of fire frequency and season on herbaceous vegetation in savannas of the Kruger National Park, South Africa

Aims: The long-termeffects of changing fire regimes on the herbaceous component of savannas are poorly understood but essential for understanding savanna dynamics. We present results from one of the longest running (>44 years) fire experiments in savannas, the experimental burn plots (EBPs), which is located in the Kruger National Park (South Africa) and encompasses four major savanna vegetation types that span broad spatial gradients of rainfall (450–700mm) and soil fertility. Methods: Herbaceous vegetation was sampled twice in the EBPs using a modified step-point method, once prior to initiation of the experiment (1954) and again after 44–47 years. Different combinations of three fire frequency (1-, 2- and 3-year return intervals) and five season (before the first spring rains, after the first spring rains, mid-summer, late summer and autumn) treatments, as well as a fire exclusion treatment, were applied at the plot level (;7 ha each), with each treatment (n = 12 total) replicated four times at each of the four sites (n = 192 plots total). The effects of long-term alterations to the fire regime on grass community structure and composition were analyzed separately for each site. Important Findings: Over the 44+ years duration of the experiment, fires were consistently more intense on sites with higher mean annual rainfall (>570 mm), whereas fires were not as intense or consistent for sites with lower and more variable rainfall (<510 mm) and potentially higher herbivory due to greater soil fertility. Because the plots were open to grazing, the impacts of herbivory along with more variable rainfall regimes likely minimized the effects of fire for the more arid sites. As a consequence, fire effects on grass community structure and composition were most marked for the higher rainfall sites and generally not significant for the more arid sites. For the high-rainfall sites, frequent dry season fires (1- to 3-year return intervals) resulted in high grass richness, evenness and diversity, whereas fire exclusion and growing season fires had the lowest of these measures and diverged the most in composition as the result of increased abundance of a few key grasses. Overall, the long-term cumulative impacts of altered fire regimes varied across broad climatic and fertility gradients, with fire effects on the grass community decreasing in importance and herbivory and climatic variability likely having a greater influence on community structure and composition with increasing aridity and soil fertility