scholarly journals Epidemiology of gastrointestinal helminths infections in Dorper sheep in a semi-arid area of Kenya

2004 ◽  
Vol 71 (3) ◽  
Author(s):  
C.J. Ng'ang'a ◽  
N. Maingi ◽  
W.K. Munyua ◽  
P.W.N. Kanyari
Keyword(s):  
Age Groups ◽  
Dry Season ◽  
Arid Area ◽  
Wet Season ◽  
Weather Factors ◽  
Gastrointestinal Helminths ◽  
Faecal Samples ◽  
Dorper Sheep ◽  
Short Rains ◽  
Semi Arid

A survey on the prevalence and intensity of infection with gastrointestinal helminths of Dorper sheep in relation to age and weather factors was carried out on a ranch in Kajiado district, a semi-arid area of Kenya for a period of 13 months (May 1999 to May 2000). Faecal samples from lambs (3 months to 1 year), yearlings (1-2 years) and adult breeding ewes (2-4 years) were examined for helminth egg output and helminth genus composition at 3-week intervals. The results indicated that the prevalence of strongyle and tapeworms infections were highest for lambs, followed by the adult breeding ewes and then for the yearlings. In all age groups the proportions of infected animals were higher during the wet season than in the dry season for both nematodes and tapeworms. The mean strongyle egg counts were higher during the dry season for lambs, but were higher during the wet season for the other age groups. Mixed strongyle infections were detected, with Trichostrongylus (55 %), Haemonchus (28 %), Cooperia (10.5 %) and Oesophagostomum (6.5 %) being the most frequently encountered genera throughout the study period. The trends in strongyle faecal egg counts indicated the occurrence of hypobiosis, with resumption of development towards the end of the dry season and at the onset of the short rains in October and November. Self-cure was also observed in September and November in all age groups, although less frequently in lactating ewes. The prevalence and intensities of infection with gastrointestinal helminths in this area appeared to be influenced by the age of the host and weather factors.

Growth Strategies of Eucalyptus camaldulensis Dehnh. At Three Sites in Northern Australia

1994 ◽  
Vol 21 (5) ◽  
pp. 653 ◽  
Author(s):  
A Gibson ◽  
EP Bachelard ◽  
KT Hubick
Keyword(s):  
Gas Exchange ◽  
Shoot Growth ◽  
Eucalyptus Camaldulensis ◽  
Dry Season ◽  
Growth Strategies ◽  
Wet Season ◽  
Wind Speeds ◽  
The North ◽  
Air Temperatures ◽  
Semi Arid

The morphology and physiology of trees of Eucalyptus camaldulensis growing in the field at two monsoonal and one semi-arid location were compared. In the wet season, shoot growth at the monsoonal locations was similar and larger than that at the semi-arid location. In the dry season, new shoot growth at the more humid monsoonal location (Petford) was similar to growth in the wet season while at the less humid (Katherine) and the semi-arid (Tennant Creek) locations, shoot growth was foreshortened and the leaves had larger dry weights per unit area. In the summer wet season, leaves on both the north and south sides of the trees were maintained at or below (by up to 5�C) air temperatures throughout the day except for north facing leaves at Petford which were consistently above (by up to 3�C) air temperatures. Midday gas exchange in the dry season at both monsoonal localities was restricted to trees at the water's edge, whereas most trees, including those at drier sites, at the semi-arid location exhibited significant rates of gas exchange. The results, which are discussed in relation to environmental variables (vapour pressure deficits, wind speeds) to which the trees are exposed, and to previous results obtained in the glasshouse, indicate that the differences in shoot growth and physiology are adaptations to the environment in which the trees have evolved.

Enhancing food security in semi-arid eastern Indonesia through permanent raised-bed cropping: a review

1999 ◽  
Vol 39 (8) ◽  
pp. 1035 ◽  
Author(s):  
D. E. Van Cooten ◽  
A. K. Borrell
Keyword(s):  
Water Supply ◽  
Food Production ◽  
Crop Production ◽  
Ground Cover ◽  
Dry Season ◽  
Wet Season ◽  
Additional Food ◽  
Eastern Indonesia ◽  
Raised Bed ◽  
Semi Arid

Summary. Much of south-eastern Indonesia is mountainous and characterised by a semi-arid tropical environment. Soil erosion is a significant environmental problem facing the region, affecting both productivity of the land and water quality. The challenge for the region is to secure year-round food production in such a fragile environment. More than 90% of rain falls in a distinct wet season between November and April. Therefore, cropping in this region is dependent on matching crop growth with water supply. In particular, crop production depends on the efficient use of rainfall during the wet season, including avoidance of waterlogging, and efficient use of stored soil water during the dry season. This paper summarises the results of a series of experiments undertaken in West Timor, Indonesia, between 1993 and 1999 aimed at developing a raised-bed cropping system. The objective of these studies was to better utilise the more fertile alluvial soils that are often susceptible to waterlogging during the wet season, allowing a range of crops to be grown in addition to rice. Raised beds of height 0.2 m and width 1.5 m were constructed either manually or with an 8.5 hp two-wheeled hand tractor. A range of crops including soybeans, sorghum, maize, pigeon pea, yam bean and cassava were successfully grown on raised beds in the wet season in addition to rice, indicating that raised-bed technology overcomes the constraints of waterlogging in the wet season. Soybeans grew particularly well on raised beds, with December-sown crops producing almost twice the yield of January-sown crops (2.6 v. 1.4 t/ha). For rice and soybeans, early sown crops were better able to match growth with water supply, thereby avoiding end-of-season drought. Early sowing and harvesting of wet season crops enables a drought-resistant crop such as sorghum to be planted in lateMarch or early April, utilising the stored soil moisture for grain production and also maintaining ground cover in the dry season. It is argued that cropping systems based on permanent raised beds can reduce erosion in 2 ways. First, raised beds are a permanent structure and, with the inter-cropping and relay-cropping proposed, crops can provide all-year ground cover in lowland areas. Second, if sufficient food and cash crops are grown on raised beds to meet the basic needs of subsistence farmers, then upland cropping on steep slopes can be replaced by a variety of tree species, providing additional food, fodder, firewood and medicines. Together, these strategies have the capacity to enhance food production and security in the semi-arid areas of eastern Indonesia.

Three new species of Alepia Enderlein (Diptera, Psychodidae, Psychodinae) from the Brazilian semi-arid region

Zootaxa ◽  
2008 ◽  
Vol 1805 (1) ◽  
pp. 52 ◽  
Author(s):  
FREDDY BRAVO
Keyword(s):  
New Species ◽  
Arid Region ◽  
Dry Season ◽  
Arid Area ◽  
Northeastern Brazil ◽  
Three New Species ◽  
Semi Arid Region ◽  
Low Precipitation ◽  
Semi Arid

Three new species of Alepia Enderlein from the semi-arid region of Bahia State, northeastern Brazil are described: A. montana sp. nov., A. arenivaga sp. nov., and A. fervida sp. nov. Currently, eight species of Psychodidae are known from the semi-arid area (including the three species here described)—a region characterized by a long dry season (6–11 months) and low precipitation levels (300–1000 mm/year). A list of the eight species of Psychodidae from the Brazilian semi-arid region is provided.

scholarly journals Epidemiological studies of Schistosoma mattheei infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe

2006 ◽  
Vol 73 (3) ◽  
Author(s):  
D.M. Pfukenyi ◽  
S. Mukaratirwa ◽  
A.L. Willingham ◽  
J. Monrad
Keyword(s):  
Intermediate Host ◽  
Climatic Factors ◽  
Seasonal Pattern ◽  
Chemical Properties ◽  
Dry Season ◽  
Wet Season ◽  
Adult Cattle ◽  
Host Snail ◽  
Faecal Samples ◽  
Hot Dry Season

During the period between January 1999 and December 2000, the distribution and seasonal patterns of Schistosoma mattheei infections in cattle in the highveld and lowveld communal grazing areas of Zimbabwe were determined through monthly coprological examination. Faecal samples of cattle were collected from 12 and nine dipping sites in the highveld and lowveld communal grazing areas, respectively. Patterns of distribution and seasonal fluctuations of the intermediate host-snail populations and the climatic factors influencing the distribution were also determined at monthly intervals from November 1998 to October 2000, a period of 24 months, in six dams and six streams in the highveld and nine dams in the lowveld communal grazing areas. Monthly, each site was sampled for relative snail density, the vegetation cover and type, and physical and chemical properties of the water. Mean monthly rainfall and temperature were recorded. Snails collected at the same time were individually examined for shedding of cercariae of S. mattheei and Schistosoma haematobium. A total of 16 264 (5 418 calves, 5 461 weaners and 5 385 adults) faecal samples were collected during the entire period of study and 734 (4.5 %) were positive for S. mattheei eggs. Significantly higher prevalences were found in the highveld compared to the lowveld (P < 0.001), calves compared to adult cattle (P < 0.01) and the wet season compared to the dry season (P < 0.01). Faecal egg output peaked from October/ November to March / April for both years of the study. Bulinus globosus, the snail intermediate host of S. mattheei was recorded from the study sites with the highveld having a significantly higher abundance of the snails than the lowveld (P < 0.01). Monthly densities of B. globosus did not show a clearcut pattern although there were peaks between March / May and September / November. The mean num ber of snails collected was positively correlated with the water plants Nymphaea caerulea and Typha species. Overall, 2.5 % of B. globosus were shedding Schistosoma cercariae. In the highveld, 2.8 % of B. globosus were infected with schistosome cercariae and 1.5 % in the lowveld, with the figures at individual sites ranging from 0-18.8 % in the highveld and from 0-4.5 % in the lowveld. The cercariae recorded here were a mixture of S. mattheei and S. haematobium since they share the same intermediate host. The transmission of Schistosoma cercariae exhibited a marked seasonal pattern, being more intensive during the hot, dry season (September / November).

Survival of unfedRhipicephalus appendiculatus(Acarina: Ixodidae) in relation to host resistance and environmental factors in Kenya

1990 ◽  
Vol 80 (3) ◽  
pp. 251-258 ◽  
Author(s):  
J.W. Chiera ◽  
D.K. Punyua
Keyword(s):  
Environmental Factors ◽  
Host Resistance ◽  
Initial Period ◽  
Rhipicephalus Appendiculatus ◽  
Dry Season ◽  
Survival Times ◽  
Wet Season ◽  
Weather Factors ◽  
Hot Dry Season ◽  
Similar Survival

AbstractMean survival times for unfed ticks,Rhipicephalus appendiculatusNeumann exposed initially during the hot dry season (January) in Kenya were significantly higher than those of ticks exposed during the wet season (May). This was partly due to the timing of the next hot dry season which triggered the beginning of decline in survival, and partly due to the overall severity of the weather. The implication is that the time when the ticks feed affects the survival of the subsequent instar. The mean survival times for nymphs exposed initially during the wet and the hot dry seasons were 30 weeks and 44 weeks, respectively. Those for adult ticks ranged between 59–75 weeks and 62–79 weeks, respectively. Maximum survival times were, however, similar for adults but not for nymphs. Adult ticks had an initial period of 32–48 weeks of excellent survival, apparently independent of weather factors. Thereafter, mortality rates and adverse environmental factors were correlated. The survival of ticks fed on hosts of differing resistance status was also different. The most resistant host produced the smallest adult ticks and these gave the lowest survival, and vice versa. Male and female ticks from highly resistant hosts had similar survival, but the females from a moderately resistant host survived significantly better than the males. These results indicate the importance of weather and host resistance inR. appendiculatussurvival.

scholarly journals General procedure to initialize the cyclic soil water balance by the Thornthwaite and Mather method

2010 ◽  
Vol 67 (1) ◽  
pp. 87-95 ◽  
Author(s):  
Durval Dourado-Neto ◽  
Quirijn de Jong van Lier ◽  
Klaas Metselaar ◽  
Klaus Reichardt ◽  
Donald R. Nielsen
Keyword(s):  
Water Balance ◽  
Soil Water ◽  
General Procedure ◽  
Water Storage ◽  
Dry Season ◽  
Soil Water Balance ◽  
Soil Water Storage ◽  
Wet Season ◽  
Water Balance Components ◽  
Semi Arid

The original Thornthwaite and Mather method, proposed in 1955 to calculate a climatic monthly cyclic soil water balance, is frequently used as an iterative procedure due to its low input requirements and coherent estimates of water balance components. Using long term data sets to establish a characteristic water balance of a location, the initial soil water storage is generally assumed to be at field capacity at the end of the last month of the wet season, unless the climate is (semi-) arid when the soil water storage is lower than the soil water holding capacity. To close the water balance, several iterations might be necessary, which can be troublesome in many situations. For (semi-) arid climates with one dry season, Mendonça derived in 1958 an equation to quantify the soil water storage monthly at the end of the last month of the wet season, which avoids iteration procedures and closes the balance in one calculation. The cyclic daily water balance application is needed to obtain more accurate water balance output estimates. In this note, an equation to express the water storage for the case of the occurrence of more than one dry season per year is presented as a generalization of Mendonça's equation, also avoiding iteration procedures.

scholarly journals Seasonal evolution of faecal egg output by gastrointestinal worms in goats on communal farms in eastern Namibia

2003 ◽  
Vol 70 (4) ◽  
Author(s):  
F.F. Kumba ◽  
H. Katjivena ◽  
G. Kauta ◽  
E. Lutaaya
Keyword(s):  
Parasitic Infection ◽  
Small Ruminants ◽  
Dry Season ◽  
Least Square ◽  
Wet Season ◽  
Monthly Basis ◽  
Faecal Samples ◽  
Hot Dry Season ◽  
Food Shortages ◽  
Worm Problem

As a more detailed continuation of a previous study, faecal samples for worm egg counts were collected per rectum from ten marked adult animals in selected flocks of goats, in each of six villages evenly spread out in the communal farming district of Okakarara in eastern Namibia. The study was conducted on a monthly basis from August 1999 to July 2000. Average faecal worm egg counts (FECs) were highest during the warm-wet season, much lower during the cold-dry months and moderate during the hot-dry season. Least square means of FECs were 2 140, 430 and 653 per gram of faeces for the three seasons, respectively. Seasonal variation in egg counts was significant (P < 0.0001). Gastrointestinal strongyles, and to a lesser extent Strongyloides species, were the predominant parasite groups identified in goats. Kidding rates peaked in the cold-dry season and mortality rates in the hot-dry season. Results of this study suggest that gastrointestinal parasitism may be a problem that accentuates the effect of poor nutrition on small ruminants during the season of food shortages in the east of Namibia and that the use of FECs per se to assess the severity of gastrointestinal parasitic infection in goats followed by chemoprophylactic strategic and / or tactical treatment, may not be the best approach to addressing the worm problem under resource-poor conditions. The use of the FAMACHA(c) system that identifies severely affected animals for treatment is technically a better option for communal farmers.

scholarly journals An integrodifference model for vegetation patterns in semi-arid environments with seasonality

2020 ◽  
Vol 81 (3) ◽  
pp. 875-904
Author(s):  
Lukas Eigentler ◽  
Jonathan A. Sherratt
Keyword(s):  
Seed Dispersal ◽  
Spatial Patterns ◽  
Dry Season ◽  
Vegetation Patterns ◽  
Arid Environments ◽  
Wet Season ◽  
Temporal Separation ◽  
Pde Model ◽  
Dispersal Events ◽  
Semi Arid

Abstract Vegetation patterns are a characteristic feature of semi-deserts occurring on all continents except Antarctica. In some semi-arid regions, the climate is characterised by seasonality, which yields a synchronisation of seed dispersal with the dry season or the beginning of the wet season. We reformulate the Klausmeier model, a reaction–advection–diffusion system that describes the plant–water dynamics in semi-arid environments, as an integrodifference model to account for the temporal separation of plant growth processes during the wet season and seed dispersal processes during the dry season. The model further accounts for nonlocal processes involved in the dispersal of seeds. Our analysis focusses on the onset of spatial patterns. The Klausmeier partial differential equations (PDE) model is linked to the integrodifference model in an appropriate limit, which yields a control parameter for the temporal separation of seed dispersal events. We find that the conditions for pattern onset in the integrodifference model are equivalent to those for the continuous PDE model and hence independent of the time between seed dispersal events. We thus conclude that in the context of seed dispersal, a PDE model provides a sufficiently accurate description, even if the environment is seasonal. This emphasises the validity of results that have previously been obtained for the PDE model. Further, we numerically investigate the effects of changes to seed dispersal behaviour on the onset of patterns. We find that long-range seed dispersal inhibits the formation of spatial patterns and that the seed dispersal kernel’s decay at infinity is a significant regulator of patterning.

scholarly journals Vegetation indices as proxies for spatio-temporal variations in water availability in the Rio Santa valley (Peruvian Andes)

2021 ◽  
Author(s):  
Lorenz Hänchen ◽  
Cornelia Klein ◽  
Fabien Maussion ◽  
Wolfgang Gurgiser ◽  
Pierluigi Calanca ◽  
...  
Keyword(s):  
Water Availability ◽  
Rainy Season ◽  
Vegetation Indices ◽  
Growing Season ◽  
Dry Season ◽  
Season Length ◽  
Wet Season ◽  
Peruvian Andes ◽  
Spatio Temporal ◽  
Semi Arid

Abstract. In the semi-arid Peruvian Andes, the growing season is mostly determined by the timing of the onset and retreat of the wet season, to which annual crop yields are highly sensitive. Recently, local farmers in the Rio Santa basin (RSB) reported decreasing predictability of the onset of the rainy season and further challenges related to changes in rainfall characteristics. Previous studies based on time series of local rain gauges however, did not find any significant changes in either the timing or intensity of the wet season. Both in-situ and satellite rainfall data for the region lack the necessary spatial resolution to capture the highly variable rainfall distribution typical for complex terrain, and are often questionable in terms of quality and temporal consistency. To date, there remains considerable uncertainty in the RSB regarding hydrological changes over the last decades. In this study, we overcome this limitation by exploiting satellite-derived information on vegetation greenness to reveal a robust and highly resolved picture of recent changes in rainfall and vegetation phenology across the region: As the semi-arid climate causes water availability (i.e. precipitation) to be the key limiting factor for plant growth, patterns of precipitation occurrence and the seasonality of vegetation indices (VIs) are tightly coupled. Therefore, VIs can serve as an integrated proxy of rainfall. By combining MODIS Aqua and Terra VIs for 2000–2020 and several datasets of precipitation, we explore recent spatio-temporal changes in vegetation and water availability. Furthermore, we examine their links to El Niño Southern Oscillation (ENSO). While different rainfall datasets tend to be incoherent in the period of observation, we find significant greening over the majority of the RSB domain in VI data, particularly pronounced during the dry season (Austral winter). This indicates an overall increase of plant available water over time. The rainy season onset and consequently the start of the growing season (SOS) exhibits high inter-annual variability and dominates the growing season length (LOS). The end of the growing season (EOS) is significantly delayed in the analysis which matches the observed dry-season greening. By partitioning the results into periods of three stages of ENSO (neutral, Niño, Niña), we find an earlier SOS and an overall increased season length in years associated with El Niño. However, the appearance of Niño/Niña events during the analysed period cannot explain the observed greening and delayed EOS. While our study could not corroborate anecdotal evidence for recent changes in the SOS, we confirm that the SOS is highly variable and conclude that rainfed farming in the RSB would profit from future efforts being directed towards improving medium-range forecasts of the rainy season onset.

scholarly journals SEASONAL EFFECTS ON OESTRUS PATTERNS AND PROGESTERONE PROFILES OF YANKASA EWES OF DIFFERENT AGE-GROUPS IN THE SUB-HUMID TROPICS

2021 ◽  
Vol 28 (2) ◽  
pp. 211-216
Author(s):  
B. S. OLADIMEJI ◽  
O. A. OSINOWO, ◽  
J. P. ALAWA ◽  
J. O. HAMBOLU
Keyword(s):  
Age Groups ◽  
Reproductive Behaviour ◽  
Dry Season ◽  
Seasonal Effects ◽  
Age Group ◽  
Wet Season ◽  
Serum Progesterone ◽  
Oestrus Cycle ◽  
Hot Dry Season ◽  
The Mean

Oestrus patterns and serum progesterone profiles of 10 adult and 10 yearling Yankasa ewes were investigated in the late hot-dry and late-wet seasons in the subhumid tropical climate of Zaria, Nigeria. The proportions of ewes which came on heat once, twice or thrice within the experimental periods in the late hot-dry and late-wet seasons were 25, 15 and 0%, and 5, 10 and 85% respectively, while mean oestrous cycle length was significantly longer (P<0.001) in the hot-dry season than in the late-wet season (30.9 vs 18.4 days) due to the higher incidence of anoestrus in the former. However, the mean duration of oestrus was not affected by season. Mean serum progesterone levels were significantly (P<0.05) higher in the late-wet season than in the late hot-dry season (1.57 vs 0.52 ng/ml). However, there was a highly significant (P<0.001) interaction between season and age group in mean serum progesterone levels due to a relatively greater depression in progesterone levels in yearling ewes during the hot-dry season compared with adult ewes. The observed disruptions in the oestrus cycle and serum progesterone levels of the ewes in the hot-dry season confirm the adverse effect of heat stress on the reproductive behaviour of ewes.

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