Pre-dry Season Research Articles

SEASONAL VARIATION IN WATER QUALITY INDEX OF THE LAKE BOSOMTWE BIOSPHERE RESERVE

Lake Bosomtwe has been subjected to anthropogenic perturbations that provide different scales of environmental stimuli in response to seasonal variation. This situation can overwhelm the capacity of lake to mitigate the impact on the water quality. Knowledge of seasonality will enhance the predictability of the water quality trends to advance management of the lake. The seasonal pattern of levels of physicochemical and nutrient parameters was examined, from March 2018 to February 2020, using the Canadian Council of Ministers of the Environment Water Quality Index model. Temperature, pH, alkalinity, turbidity, dissolved oxygen, total hardness, total dissolved solids, total suspended solids, biochemical oxygen demand, nitrate, phosphate, sulphate, iron, lead, and zinc were studies. The results showed a decline in water quality from ‘fair’ status in the pre-rainy (65.7%) and rainy (67.2%) seasons through ‘marginal’ in the pre-dry seasons (46.5%) to poor in the dry seasons (44%). The lake is therefore losing its natural protection to the extent of occasional for the pre-rainy and rainy seasons, frequently for pre-dry seasons, and almost all the time for dry season, the period of low lake water volume and availability and hence high dependence. Thus, the threat of human and ecological health hazard associated with aquatic pollution is ordered by seasonality; being heightened in the dry season with alkalinity, sulphate, iron, temperature, total suspended solids and turbidity as the parameters of more concern. This provides adequate ground for a call for elaborate and systematic plan of action to manage the lake for sustainability.

Physicochemical Characters of Mosquitoes Natural Breeding Habitats: First Record in High Dengue Hemorrhagic Fever Cases Area, East Java, Indonesia

This research aims to identify physicochemical characteristics in natural breeding habitats/ phytotelmata of dengue vector—including Aedes (Stegomyia) aegypti and Aedes (Stegomyia) albopictus. The research was conducted during rainy season and pre-dry season (from January to June 2017) in the region with the high cases of Dengue Hemorrhagic Fever (DHF). The entomological survey was carried out by stratified random sampling in urban and rural areas in order to find potential breeding habitats, every natural breeding habitats in sampling location were checked for the presence of Aedes larvae. Physicochemical characters that consist of temperature, turbidity, carbon dioxide, ammonia, nitrate, sulphate, pH and dissolved oxygen were recorded. Larval species were taken and then identifying activities were conducted in the Laboratory of Entomology. Data were analysed using the Chi-square test. Results showed that only dissolved oxygen that significantly associated with larval abundance (p=0.039). while others are not significantly associated. Whereas, other characters are associated with each other, carbon dioxide associated with the ammonia and sulphate (p=0.001; p=0.028). Turbidity associated with the dissolved oxygen (p=0.022) and pH associated with nitrate (p=0.001).

Widespread increase of boreal summer dry season length over the Congo rainforest

Dry season length strongly influences tropical rainforest vegetation and is largely determined by precipitation patterns1,2. Over the Amazon, the dry season length has increased since 1979 and severe short-term droughts have occurred3,4. However, similar changes have not been investigated for the world’s second largest rainforest, the Congo Basin, where long-term drying and large-scale declines in forest greenness and canopy water content were reported5. Here we present observational evidence for widespread increases in the boreal summer (June–August) dry season length over the Congo Basin since the 1980s, from both hydrological and ecological perspectives. We analysed both dry season onset and dry season end via multiple independent precipitation and satellite-derived vegetation datasets for the period 1979–2015. The dry season length increased by 6.4–10.4 days per decade in the period 1988–2013, primarily attributed to an earlier dry season onset and a delayed dry season end. The earlier dry season onset was caused by long-term droughts due to decreased rainfall in the pre-dry season (April–June). The delayed dry season end resulted from insufficiently replenished soil moisture, which postpones the start of the next wet season and hinders vegetation regrowth. If such changes continue, the enhanced water stress in a warming climate may affect the carbon cycle and alter the composition and structure of evergreen rainforest1,6. The length of the dry season over tropical forests is a determining factor of ecosystem health and drought risk. Hydroclimate and vegetation data show that dry season length has increased over the Congo rainforest since the 1980s, owing to both an earlier dry season onset and a delayed end.

Evaluation of the ECMWF System 4 climate forecasts for streamflow forecasting in the Upper Hanjiang River Basin

AbstractThis paper assesses the potential of the European Centre for Medium-Range Weather Forecasts (ECMWF) System 4 forecasts and investigates the post-processing precipitation to enhance the skill of streamflow forecasts. The investigation is based on hydrological modelling and is conducted through the case study of the Upper Hanjiang River Basin (UHRB). A semi-distributed hydrological model, TsingHua Representative Elementary Watershed (THREW), is implemented to simulate the rainfall–runoff processes, with the help of hydrological ensemble prediction system (HEPS) approach. A post-processing method, quantile mapping method, is applied to bias correct the raw precipitation forecasts. Then we evaluate the performance of raw and post-processed streamflow forecasts for the four hydrological stations along the mainstream of Hanjiang River from 2001 to 2008. The results show that the performance of the streamflow forecasts is greatly enhanced with post-processing precipitation forecasts, especially in pre-dry season (November and December), thus providing useful information for water supply management of the central route of South to North Water Diversion Project (SNWDP). The raw streamflow forecasts tend to overpredict and present similarly to forecast accuracy with the extended streamflow prediction (ESP) approach. Streamflow forecast skill is considerably improved when applying post-processing method to bias correct the ECMWF System 4 precipitation forecasts.

Retrospective analysis of Newcastle disease diagnosed at the poultry clinic of Ahmadu Bello University, Zaria, Nigeria

Newcastle disease (ND) is a highly contagious viral disease of domestic and wild birds with devastating impact on poultry health and production. Many vaccines and vaccination schedules are in use in controlling the disease but prevention and control are still a problem. A ten-year retrospective study (2002-2011) of Newcastle disease and other poultry diseases diagnosed at the Poultry Clinic of Ahmadu Bello University Veterinary Teaching Hospital (ABUVTH), Zaria, Kaduna, Nigeria was conducted. Out of 2,649 cases of poultry presented, 43.9% (1,164 cases) were confirmed as ND. The highest number of cases of the disease was in August followed by July and May. The cases of ND were observed to be higher in the rainy season (July to September), but it seems to be 1.43 times more likely to occur during pre-dry season (October to December). Most of the cases of ND were recorded in chickens and turkeys. Birds between the ages of 9 and 20 weeks were 2.01 times more likely to suffer from ND than younger birds. Most of the cases of ND were reported in birds that were vaccinated against ND than non-vaccinated ones. It was recommended that monitoring of Newcastle disease antibody titre should be intensified during rainy season and birds should be vaccinated against the disease as at when due. Keywords: Newcastle disease, Poultry, Seasonal distribution, Vaccine, Zaria

Prevalence of Newcastle Disease in Gombe, Northeastern Nigeria: A Ten-Year Retrospective Study (2004 – 2013)

Aim: A ten – year retrospective study was conducted with the aim to determine the prevalence of Newcastle Disease (ND) in relation to other poultry diseases diagnosed in the State area veterinary clinics. Study Design: Retrospective study. Place and Duration of the Study: This study was conducted in Gombe State, Northeastern Nigeria. Case files from Tashan Dukku and Pantami area veterinary clinics in Gombe metropolis were reviewed for the study. File of cases of poultry diseases reported between January 2004 and December 2013 were studied. Original Research Article Lawal et al.; BMRJ, 6(6): 367-375, 2015; Article no.BMRJ.2015.088 368 Methodology: Information on ND in poultry only was extracted from the clinical records and the non – ND cases were considered together as a group. A case of ND was defined as a farm that reported an outbreak of diseases diagnosed as ND based on history, clinical signs and post – mortem findings in the study area. Results: Of 9970 cases of poultry diseases studied, 5531 (55.50%) were cases of ND (P >0.05). The Year Specific Rate (YSR) ranged from 51.5% (OR = 1.0) in 2005 to 63.3% (OR = 1.63; 95%CI: 0.81 – 2.45) in 2006 (P >0.05). The Monthly Specific Rates (MSR) of ND was 66.5% (OR = 5.94; 95%CI: 4.57 – 7.31) in October, 64.4% (5.42; 4.29 – 6.55) in December, 64.2% (5.36; 4.17 – 6.55) in January, 61.3% (4.74; 3.61 – 5.87) in November, 27.0% (1.10; 0.15 – 2.05) in June and 25.1% in July. ND was 3.4 times more likely to occur during the Pre-dry season (October – December) and 3.0 times more likely to occur during the Dry season (January March) as compared with the other seasons of the year. Conclusion: The study revealed that ND is still endemic in Gombe State – Nigeria, with peak outbreaks during dry and cold seasons. Purchasing day old chicks from farms known to give booster vaccinations to their parent stock hens, vaccinating chicks with vaccines that are immunogenic, use of thermo-stable vaccines for routine vaccinations of chicks and maintenance of strict bio-security measures are recommended to reduce the prevalence of the disease in the study area.

Predictable Habitat Associations of Four Crab Species Across the Low Intertidal Landscape of a Tropical Estuary over Time

To address the increasing threats from urbanization and climate change, an improved understanding of ecosystem processes at large, estuary-wide scales is required. Intertidal crabs contribute to estuarine functioning via trophic interactions and ecosystem engineering. Previous studies on crab spatial distribution patterns have focused on site- or transect-specific scales and consequently do not address spatial distribution patterns relative to the full environmental landscape within estuaries. In the present study, predictive habitat modeling using data collected with high replication photographic sampling revealed distinct habitat associations for four crab species across the low intertidal landscape (between mean low tide at spring and the edge of the mangrove forest) of Stuart Creek, northeast Australia (19° 17′ S, 146° 50′ E). Seasonal sampling was conducted on 10 dates from April 2009 to July 2011. Uca coarctata occurred nearly everywhere but achieved highest abundance on intertidal banks with pneumatophores and at least some canopy overhang. Uca seismella occurred in habitats with low intertidal vegetation and almost no structural complexity. By contrast, Metopograpsus frontalis was associated with habitats with at least 4 % of the substratum containing structure, and Metopograpsus latifrons with habitats with at least 22 % of the substratum containing structure. While overlap occurred between species, a taxon-specific separation of Metopograpsus spp.-dominated habitats and Uca spp.-dominated habitats was related to the availability of structural complexity, suggesting that it is a niche-defining factor. Sensitivity tests indicated high predictability of habitat associations among pre-dry, dry, pre-wet, and wet seasons from April 2009 to July 2011, suggesting high stability in spatial distribution patterns of intertidal crabs. Results provide a scientific basis for increased understanding of the spatial distribution patterns of intertidal crabs at landscape scales.

Seroprevalence, Seasonal Occurrence and Clinical Manifestation of Newcastle Disease in Rural Household Chickens in Plateau State, Nigeria

A study on seroprevalence, seasonal occurrence and clinical manifestation of Newcastle Disease Virus (ND) among rural household chickens and Live Birds Markets (LBM) was conducted using haemagglutination Inhibition Test (HI) and questionnaires. A total of 1, 208 chickens reared under extensive management system in four Local Government Areas (LGAs) of Plateau State were used for the study. The seroprevalence of ND virus antibodies in rural chickens showed that there was no statistically significant (p > 0.05) difference among the four LGAs and of the 1,208 sera tested, 51.9% had detectable antibodies to NDV but only 14.1% of the chickens had HI antibody titre of > 4log which was considered as protective. 2 About 86.2% of the chickens sampled were at risk of suffering from clinical ND. Newcastle disease outbreaks occurred year round in the villages sampled with the highest incidence of 86.6% observed from November to March (Dry season) and September to October, 8.31% (Pre-dry season). During outbreaks of ND, infected birds exhibit the following major clinical signs; nervous signs (32.4%), weakness (16.6%), whitish/greenish diarrhea (16.2%), coughing/sneezing 13.6%, anorexia 9.39% and others 11.8%. It was concluded that the prevalence of ND in the four LGAs of Plateau State is high. At the time of the study over 80% of rural chickens in Plateau State were at risk of dying from ND when exposed to a virulent NDV. It is therefore recommended that vaccination and improved management practices as a means of prevention against ND before the period of outbreaks should be instituted.

Seasonal leaf phenotypes in the canopy of a tropical dry forest: photosynthetic characteristics and associated traits.

We evaluated the hypothesis that photosynthetic traits differ between leaves produced at the beginning (May) and the end (November-December) of the rainy season in the canopy of a seasonally dry forest in Panama. Leaves produced at the end of the wet season were predicted to have higher photosynthetic capacities and higher water-use efficiencies than leaves produced during the early rainy season. Such seasonal phenotypic differentiation may be adaptive, since leaves produced immediately preceding the dry season are likely to experience greater light availability during their lifetime due to reduced cloud cover during the dry season. We used a construction crane for access to the upper canopy and sampled 1- to 2-month-old leaves marked in monthly censuses for six common tree species with various ecological habits and leaf phenologies. Photosynthetic capacity was quantified as light- and CO2-saturated oxygen evolution rates with a leaf-disk oxygen electrode in the laboratory (O2max) and as light-saturated CO2 assimilation rates of intact leaves under ambient CO2 (Amax). In four species, pre-dry season leaves had significantly higher leaf mass per unit area. In these four species, O2max and Amax per unit area and maximum stomatal conductances were significantly greater in pre-dry season leaves than in early wet season leaves. In two species, Amax for a given stomatal conductance was greater in pre-dry season leaves than in early wet season leaves, suggesting a higher photosynthetic water-use efficiency in the former. Photosynthetic capacity per unit mass was not significantly different between seasons of leaf production in any species. In both early wet season and pre-dry season leaves, mean photosynthetic capacity per unit mass was positively correlated with nitrogen content per unit mass both within and among species. Seasonal phenotypic differentiation observed in canopy tree species is achieved through changes in leaf mass per unit area and increased maximum stomatal conductance rather than by changes in nitrogen allocation patterns.

Utilization of common grasses by goats in two seasons

The effect of feeding freshly-cut common grasses on growth performance of Black Bengal goats during the pre-monsoon and pre-dry season was evaluated. Four castrated goats of 5-6 months age with a mean initial body weight were 11.17 and 10.23 kg for pre-monsoon and pre-dry season respectively, were used as experimental animal. Nutrient component, intake of different nutrients and its effect on body weight changes were determined. Common grass harvested during the pre-monsoon season contained higher nitrogen (15.6 g/kg) and less DM (196.8 g/kg) than the grass harvested in pre-dry season where nitrogen was 12.8 g/kg and DM was 454.9 g/kg. Intake of DM, OM, N, and NDF were 73.12 g, 67.12 g, 964.68 mg and 50.14 g/kg W0.75 respectively in pre-monsoon were higher than those in pre-dry season at p < 0.01 level of significance. Higher (p < 0.01) growth (35.71 g/day) rate was found in pre-monsoon season. It may concluded that grasses grown during the pre-monsoon season was higher nitrogen value and appeared to be more palatable.

Quantitative estimation of spermatogenesis in bulls (Bos indicus) in a tropical environment of Nigeria.

Spermatogenesis in bulls (Bos indicus) indigenous to Nigeria, and the significance of Sertoli cell index (SCI) as a measure of testicular degeneration were studied. The mean testicular weights and dimensions were lower than reported for Bos taurus breeds. The diameters of the seminiferous tubules were lower than reported for Bos taurus, although within the same range. Inter-month and intra-month variations were highly significant (P less than 0.01). A mean annual spermatogenesis of 77.60% was reported. Active spermatogenesis was observed throughout the year, with a peak during the rainy season and extending toward the pre-dry season. This was consistent with previous reports. Severe testicular degeneration was found to influence spermatogenesis. This was reflected in the decrease in SCI. Mild degeneration had no significant effect on spermatogenesis, and did not significantly change the SCI. The SCI was defined as the ratio of the number of germinal cells to the number of Sertoli cells in the same cross sections of tubules.

Significance of atrophic ovaries in livestock production in northern Nigeria.

In a study of 3000 cattle of different breeds and origin (Bos indicus and Bos taurus) in Northern Nigeria, an overall 22.7 per cent incidence of anoestrus associated with organic genital abnormalities was observed. Of this 19.3 per cent was due to ovarian atrophy. This was observed mostly during the pre-dry and dry seasons, periods of poor and inadequate feed. The average incidence of atrophic ovaries in the exotic breeds (Bos taurus) was 17.1 per cent, while an incidence of 20.4 per cent was observed in the indigenous (Bos indicus) cattle; there was no significant difference between the two groups. A relatively higher incidence of functional anoestrus (27.5 per cent) which showed no seasonal pattern and no significant difference between the breeds was observed. Inadequate nutrition was the major cause of the ovarian atrophy and subsequent anoestrus. Other clinical genital abnormalities included hypoplastic ovaries (1.9 per cent), follicular cysts (4.5 per cent), pyometra (4.5 per cent) and freemartinism (0.3 per cent). The influence of anoestrus (50 per cent total incidence) on the economic aspect of livestock production in Northern Nigeria is discussed.

Effect of scrotal streptothricosis on spermatogenesis in the bull.

Cutaneous streptothricosis was observed in 171 (13.42 per cent) out of 1274 animals examined over a period of 12 months. Eighty-six (8.30 per cent) of the 1036 bulls examined had cutaneous and scrotal streptothricosis and 85 (35.71 per cent) of the 238 cows had cutaneous streptothricosis of varying degrees. More cattle were affected during the rainy and pre-dry seasons when the condition was more extensive and severe. Histologically, moderate testicular degeneration was observed in 15 (13.6 per cent) of 110 streptothricosis-free bulls and 14 (16.3 per cent) of the 86 bulls with scrotal streptothricosis. No correlation was found between scrotal streptothricosis and testicular degeneration and, or inflammation. Average percentage spermatogenesis was 89.7 per cent for normal bulls, 91.2 per cent and 89.5 per cent for bulls with mild and moderate scrotal streptothricosis respectively and 88.0 per cent for bulls with severe scrotal streptothricosis. Two chronic cases had an average percentage spermatogenesis of 89.0 per cent. There was no correlation between the degree and extent of scrotal streptothricosis and spermatogenesis. The slight increase in the thickness of the scrotum was not observed to affect the normal course of spermatogenesis.

Spermiograms of Sokoto Gudali Bulls in Relation to Season and Ration Supplementation in Northern Nigeria

Variations in the spermiogram of eight Sokoto Gudali bulls (Bos indicus) aged 3·5 to six years and indigenous to Nigeria were studied. The bulls were divided into two comparable groups (A and B), and both groups had the same climatic conditions but different levels of nutrition. No significant differences in the percentage of sperm-cell defects, live-dead cells and volume of semen ejaculated were observed with respect to season, level of nutrition, age or body weight of the bulls. Adequate nutrition during the rainy and pre-dry seasons enhanced spermcell concentration. Some primary and secondary sperm-cell abnormalities were observed. The monthly average percentage of primary cell defects was 13 ± 0·01 and 14 ± 0·07% and of secondary defects was 15·7 ± 0·03 and 14·3 ± 0·05% for groups A and B bulls respectively. All defects were present in the ejaculate of each bull but in varying levels. In general the monthly variations in all sperm-cell defects for both groups of bulls were not significant ( P > 0·05). Sperm-cell concentration and semen volume for group A bulls showed no seasonal pattern and monthly variations were not significant ( P > 0·05), the monthly average concentration was 0·69 × 10 9 cells/ml. There was a monthly average concentration of 0·52 × 10 9 cells/ml for bulls in group B. The concentration showed a significant seasonal pattern ( P < 0·05) with a peak during the rainy season.

Seasonal Variations in Spermatogenesis in Bulls Indigenous to Nigeria

Spermatogenesis was studied in 480 pairs of testes from 240 indigenous bulls in Nigeria over a period of one year. The bulls, aged five to ten years, belonged to the nomadic Fulani herdsmen and were all in good condition at the time of slaughter. Microscopic examination of the seminiferous tubules revealed the following monthly averages: diameter 195 μm; spermatogonia-A and spermatogonia-B cells 4.2 and 6 per tubular cross-section respectively; primary spermatocytes 49.8 and round and elongated spermatids 86.4 and 30.5 per tubular cross-section respectively. Although spermatogenesis was found to be taking place (80% each month) throughout the year, examination of testicular dimensions, diameter of seminiferous tubules and activity of spermatogenic epithelium indicated increased activity during the rainy (June to September) and pre-dry seasons (October to December). Tropical heat and other environmental factors did not alter the pattern of spermatogenesis.

Reproductive Cycle of a Tropical Teiid Lizard, Neusticurus ecpleopus Cope, in Peru

Collections of a stream-dwelling South American microteiid lizard were made during a 15-month period (1967-1968) at Tingo Maria, Peru. These were analyzed in terms of four seasonal three-month periods of a year. Spermatogenesis was found in all adult males throughout the year, though testis size was significantly reduced during the dry season. The follicular developmental sequence of females is outlined. The female population was reproductively active, fecund and/or ovigerous, throughout the year. The percentage of the population with oviducal eggs dropped sharply from the pre-dry season period to the dry season, but yolked follicle size was maximal during the dry season. Evidence from additional females collected during the dry season of 1971 suggests that reductions in percentage of ovigerous females during the dry season may fluctuate from year to year, depending upon environmental conditions. It was not possible to determine the proximal environmental factors, cues, regulating the reproductive cycles in N. ecpleopus, but rainfall may be involved in the female cycle. Correlations between precipitation changes and female reproductive activities were used in an attempt to identify the selective pressures influencing the reproductive cycle. Seasonal changes in food availability to adult females and hatchlings and effects of flooding on success of incubating eggs may be some selective pressures involved. Also, reproduction in N. ecpleopus is related to two possible evolutionary strategies in lizard reproduction. ALTHOUGH MUCH IS PRESENTLY KNOWN concerning annual reproductive activities of temperate lizards, information on reproduction in tropical species is limited (Tinkle 1969; Tinkle et a-l. 1970). This is particularly unfortunate in that reproductive patterns may be important to our understanding of evolution in the tropics. The purpose of this paper is to describe the reproductive cycle of Neusticurus ecpleopus Cope, an Amazonian basin teiid (microteiid) lizard, and to relate it to what is known of the reproductive cycles of tropical lizards.