Abiotic constraints override biotic constraints in East African highland banana systems

Banana is the primary food crop in Uganda, but yields are low due to a complex of abiotic and biotic constraints. However, quantitative information on the importance, interactions, and geographic distribution of yields and constraints is scanty. We monitored yields, biotic and abiotic constraints in 159 plots in Central, South and Southwest Uganda in 2006–2007. About half the plots were on-farm demonstrations that received fertilizer (average 71N, 8P, 32 K kg ha⁻¹ year⁻¹) through a development project, the rest were ordinary farmer fields (i.e. controls). Fresh banana yields in controls were significantly (P ≤ 0.05) higher in Southwest (20 t ha⁻¹ year⁻¹) compared with Central (12 t ha⁻¹ year⁻¹) and South (10 t ha⁻¹ year⁻¹). Demonstrations yielded 3–10 t ha⁻¹ year⁻¹ more than controls. Yield losses were calculated using the boundary line approach. In Central, yield losses, expressed as percentage of attainable yield, were mainly attributed to pests (nematodes 10% loss, weevils – 6%) and suboptimal crop management (mulch 25%). In South, poor soil quality (pH – 21%, SOM – 13%, N-total – 13%, and Clay – 11%) and suboptimal crop management (weeds – 20%) were the main constraints. In Southwest, suboptimal crop management (mulch 16%), poor soil quality (K/(Ca + Mg) − 11%) and low rainfall (5%) were the primary constraints. The study revealed that biotic stresses (i.e. pests, weeds) are particularly important in Central, whereas abiotic stresses (i.e. nutrient deficiencies, drought) dominate in South and Southwest. This study concludes that (i) technologies currently available allow farmers to double yields and (ii) past research efforts have mistakenly neglected abiotic constraints.     

Participatory appraisal of foot and mouth disease in the Afar pastoral area, northeast Ethiopia: implications for understanding disease ecology and control strategy

Foot and mouth disease (FMD) is the most economically important disease of livestock that still affects extensive areas of the world. This study described the use of participatory appraisal tools such as pair-wise ranking, matrix scoring and proportional piling to assess the perception of livestock keepers about the clinical signs and epidemiological features of cattle diseases with particular emphasis on FMD. Strong agreement among informant groups (W?=?0.710; P?=?0.000) in pair wise ranking indicated that the diseases were common problem to all the selected districts. Matrix scoring of disease indicators/signs also showed strong agreement (W?=?0.504 to 0.955; P?=?0.000) that implied significant current veterinary knowledge by Afar pastoralists. Age specific means of annual incidence rates estimated by proportional piling were significantly (P?<?0.05) different but negatively correlated for FMD, CBPP and pasteurellosis. However, correlation was not significant for anthrax, blackleg and other important diseases. Age specific means of annual mortality was significantly (P?<?0.05) but negatively correlated for FMD, CBPP, pasteurellosis and other important cattle diseases with correlation coefficients of ?0.72, ?0.81, ?0.8 and ?0.55, respectively. However, correlation (r?=?0.12) was not significant for anthrax and not correlated at all for blackleg. This study indicated that pastoralists have detailed knowledge about their livestock health problems, and hence the combined use of participatory appraisal and conventional methods is essential for an ultimate disease control strategy.     

Cryptosporidium species detected in calves and cattle in Dagoretti, Nairobi, Kenya

A total of 1,734 cattle faecal samples from 296 dairy-keeping households were collected from urban settings in Nairobi, Kenya. Modified Ziehl-Neelsen staining method and an immunofluorescence assay were used to identify those samples with Cryptosporidium oocyst infection. Oocysts from positive faecal samples were isolated by Sheather's sucrose flotation method and picked from the concentrate using cover slips. Genomic DNA was extracted from 124 of the faecal samples that were positive for Cryptosporidium and was used as template for nested PCR of the 18S rRNA gene. Twenty-five samples (20?%) were PCR-positive for Cryptosporidium, and 24 of the PCR products were successfully cloned and sequenced. Sequence and phylogenetic analysis identified 17 samples (68?%) as Cryptosporidium parvum-like, four samples (16?%) as Cryptosporidium ryanae, three samples (12?%) as Cryptosporidium andersoni and one sample (4?%) as Cryptosporidium hominis. To the best of our knowledge, this is the first genotyping study to report C. parvum-like, C. andersoni and C. hominis in cattle from Kenya. The results of this study show Cryptosporidium infections in calves and cattle may be potential zoonotic reservoirs of the parasite that infects humans.     

Haematological and serum biochemical parameters of West African Dwarf goats fed dried cassava leaves-based concentrate diets

The study was conducted to investigate the effects of feeding different levels of dried cassava leaves at 0%, 20%, 40% and 60%, respectively, using guinea grass as basal feed, on the haematological and serum biochemical parameters of West African Dwarf (WAD) goats. The study lasted for 116 days during which haematological and serum biochemical parameters were monitored in 40 male goats before and after, using a completely randomized design. At the start of the experiment, packed cell volume (PCV) ranged from 21.5% to 25.5% while haemoglobin concentration (Hb) and RBC significantly (P < 0.01) ranged from 7.3 to 8.6 g/dl and 10.4 to 13.2 × 10¹²/l, respectively. White blood cells reduced significantly (P < 0.05)) from 16.4 to 11.7 × 10⁹/l) as dried cassava leaves increased in the diets. At the end of the trial, there was a slight increase in the values of PCV and Hb in the diets (P > 0.05). Lymphocyte reduced significantly (P < 0.05) from 50.0% to 63.5% in the diets. Neutrophils, however, increased (P > 0.05) at the 0% to 40% levels and reduced at the 60% level of dried cassava leaves inclusion. At the start of the experiment, values for glucose significantly (P < 0.05) ranged from 40.1 to 56.0 mg/dl. Total protein and albumin values ranged significantly (P < 0.05) from 56.0 to 68.5 g/dl and 30.6 to 38.4 g/dl, respectively. At the end of the experiment, serum creatinine increased significantly (P < 0.05) as the level of dried cassava leaves increased from 0% to 60% in the diets. The study revealed that inclusion of dried cassava leaves in the diets of West African Dwarf goats had no deleterious effects on the haematological and serum biochemical parameters of WAD goats and could therefore be included in ruminant diets up to 60%.     

Agronomic evaluation of testcrosses of drought-tolerant maize (Zea mays L.) inbred lines using different selection index methods

The present study aims at identifying potentially high-yielding testcross maize hybrids using different selection indices that consider agronomic traits other than grain yield alone. Forty-one (41) testcross hybrids developed from 20 elite drought-tolerant maize inbred lines and two inbred testers plus three hybrid checks were evaluated in the rainy seasons of 2013 and 2014 in Ogbomoso in the derived savanna agroecological zone of Nigeria. Hybrids were planted in each year in 11 × 4 lattices with two replications. Testcross hybrids and checks exhibited significant differences for all measured traits except ear height, husk cover and number of ears per plant. Grain yield of hybrids and checks averaged over the 2 years varied from 3117 to 8393 kg ha^?1 with a mean of 5935 kg ha^?1. Top 11 hybrids produced vigorous plants, each yielding >7000 kg ha^?1. Base index and multivariate index methods identified EXL11 × 9071 whereas base index and Smith–Hazel selection index methods identified EXL18 × 9071 as superior hybrids at 5% selection intensity. These hybrids will be considered for advanced breeding program and release to farmers as high-yielding drought-tolerant hybrid maize varieties in the increasingly drought-prone derived savanna agroecology of Nigeria.     

Application of crude and recombinant ELISAs and immunochromatographic test for serodiagnosis of animal trypanosomosis in the Umkhanyakude district of KwaZulu-Natal province,South Africa

A total of 231 serum samples were collected from sheep (n=9), goats (n=99) and cattle (n=123) in northeastern KwaZulu-Natal, South Africa. Trypanosome infection was detected using Trypanosoma brucei brucei crude antigen (TbbCA) and T. congolense crude antigen (TcoCA) ELISA assays. Recombinant antigen (T. evansi GM6 which consisted of 4 repeat domains, TeGM6-4r) ELISA and immunochromatographic test (ICT) were also used. Crude antigen ELISA, TeGM6-4r-ELISA and ICT detected 27.3%, 29% and 19.9% of trypanosome seropositive samples, respectively. Trypanosome infection prevalence in cattle and goats was 35.8–46.3% and 0–9.1%, respectively. Out of 9 sheep serum samples, 2–4 sera (22.2–44.4%) were positive. The detection performance of crude and recombinant antigen ELISAs was relatively similar (K=0.6–0.7); both are recommended for reference diagnosis and large scale epidemiological surveys. There is potential application for ICT in on-site diagnosis, but its sensitivity should be improved.     

Chronic bronchial disease of the cat

This discussion of chronic bronchial disease in the cat includes a discussion of the functional anatomy and physiology of the feline lung, the immunologic aspects of the disease, the role of infections, and particulate aerosols and noxious gases in the etiology and clinical course of feline asthma and chronic bronchitis, and the pathology and diagnosis of chronic bronchitis.     

Coppicing improved fallows are profitable for maize production in striga infested soils of western Kenya

Striga hermonthica (striga) weed is a major threat to crop production in sub-Saharan Africa, and short duration improved fallow species have recently been found to reduce the effects of this weed because of their ability to replenish soil nitrogen. The objective of this study was to compare the efficacy and profitability of coppicing improved fallow species (Gliricidia sepium [gliricidia], Leucaena trichandra [leucaena] and Calliandra calothyrsus [calliandra]) and non-coppicing species (Sesbania sesban [sesbania], Mucuna pruriens [mucuna], and Tephrosia vogelii [tephrosia]), in controlling striga. Natural fallow and a sole maize crop were included as control treatments. The fallow treatments were split into two and either fertilized with N or unfertilized. The results showed that coppicing fallows produced higher biomass than non-coppicing fallows. For example, Callindra (coppicing fallow species) produced 19.5 and 41.4 Mg ha⁻¹ of leafy and woody biomass, respectively after four cumulative harvests as compared with Sesbania (non-coppicing species), which produced only 2.3 and 5.9 Mg ha⁻¹ leaf and woody biomass, respectively. Improved fallows reduced striga population in proportion to the amount of leafy biomass incorporated into the soil (r = 0.87). N application increased cumulative maize yield by between 15–28% in improved fallow systems and by as much as 51–83% in the control treatments. Added total costs of the coppicing fallows did not differ significantly from those of the non-coppicing fallows and control treatments. However, the added net benefits of the coppicing fallows were significantly higher (US$ 527 for +N and 428 for −N subplots; P < 0.01) than those of the non-coppicing fallows (US$ 374 for +N and 278 for −N), and the least for the control treatments. The most profitable fallow system was Tephrosia with net added benefits of US$ 453.5 ha⁻¹ season⁻¹ without N, and US$ 586.7 ha⁻¹ season⁻¹ with added N.     

Comment on "The illusion of invariant quantities in life histories"

Nee et al. (Reports, 19 August 2005, p. 1236) used a null model to argue that life history invariants are illusions. We show that their results are largely inconsequential for life history theory because the authors confound two definitions of invariance, and rigorous analysis of their null model demonstrates that it does not match observed data.