Uganda Journal of Agricultural Science (UJAS)
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Antimicrobial resistance of Escherichia coli found in intestinal tract of Oreochromis niloticus
Get PDFAntimicrobial resistance (AMR) is an emerging public health problem worldwide. Agriculturalpractices have been suggested as one of the main contributors to the emergence andtransmission of AMR worldwide. Aquatic animals like fish have an important role to play inthe emergence and transmission of AMR strains. Escherichia coli is commensal ingastrointestinal tracts of many animals including fish, and is an indicator organism andopportunistic pathogen. It has been listed as one of the important bacteria involved in theemergence and spread of antimicrobial resistance factors. The objective of this study was toinvestigate the AMR patterns of E. coli isolated from the intestinal tract of fish within theLake Victoria basin. A total of 60 Oreochromis niloticus fish were sampled from cages, wildand earthen ponds. Distal gastrointestinal tract was recovered, crushed and streaked on violetred bile agar, incubated at 37 OC for 24 hours. The isolates confirmed biochemically as E. coliwere screened for antibiotic susceptibility against 10 commonly used antibiotics using discdiffusion method. Eighty three percent of the sampled fish were positive forE. coli. Generally,isolates were susceptible to ciprofloxacin, gentamicin, cephalexin, ceftriaxone andnitrofurantoin (100%); tetracycline, sulfamethoxazole-trimethoprim (81.8%) and nalidixicacid (72.7%). However, most of them were resistant to ampicillin and erythromycin (72.7%).The results show that fish are reservoirs of E. coli, which is resistant to some antibiotics. Thefactors responsible for the observed resistance patterns need to be followed up with moreresearch. Good aquaculture practices, surveillance and monitoring of resistant bacteria willhelp in understanding the problem of AM
Effectiveness of African catfish pituitary extracts, dagin and water flow for optimising egg production, fertilisation and hatchability in artificial spawning of Barbus altianalis
Get PDFFish inducing hormones are widely used in commercial aquaculture to facilitate continuoussupply of sufficient seed required on regular basis by the farmers. The objective of this studywas to optimise production of viable eggs for improved hatchability during artificial spawningin Barbus altianalis. Two experiments were conducted, namely (i) experiment I evaluated theefficiency of using catfish pituitary extracts in spawning of second generation broodstockscompared to that of Dagin and water flow. (ii) experiment II examined ripe running femalesfacilitated to spawn by running water only. Fish treated with pituitary extracts performedmuch better than those treated by Dagin with respect to fertilisation rates at 80.27 ± 39.57%(U = 66.5, p < 0.001) and working fecundity at 2314.40 ± 882.04 (U = 59.5, p < 0.05). However,the difference in hatchability was not significant (p > 0.05). In experiment II, hatchability andworking fecundity were significantly higher when fish were striped after 4 hours (100 degreehours at 25 oC) of running water than those striped after 10 hrs (250 degree hours) butfertilization rates were not different. The findings indicate that catfish pituitary extracts aremore effective in inducing B. altianalis to spawn than those treated with Dagin. However, theobservations made on ripe running females in both experiments suggest that they should notbe induced with any hormone. Hence, the cost of spawning could further be reduced usingrunning water, especially in wet seasons when the majority are rip
Genotypic variation for maize weevil resistance in eastern and southern Africa maize inbred lines
Get PDFThe maize weevil (Sitophilus zeamais Motschulsky) is the most destructive storage insect pest of maize (Zea mays L.) worldwide, especially among susceptible varieties. Breeding for grain resistance against the weevil is a major component of an integrated pest management strategy in maize production. The objective of this study was to identify diverse sources of weevil resistance for introgression in breeding programmes. A total of 180 inbred lines from three geographical areas were screened for maize weevil resistance. Screening was executed by infesting 50 g of maize grain with 32 newly emerged adult weevils, placed in 250 cm3 glass jars in a “no-choice” laboratory test. The grain susceptibility parameters used were F1 weevil progeny emergence, percent grain damage, median development period, Dobie’s index of susceptibility, and parental weevil mortality. New sources of weevil resistance for maize breeding were identified. Eight inbred lines were consistently resistant and, therefore, selected as potential donors for weevil resistance in the maize improvement programmes. There was significant genetic variation, and high levels of heritability (89 – 96%) for weevil resistance that suggested high potential for germplasm improvement through selection. No significant association was observed between maize weevil resistance and grain yield, suggesting that breeding for maize weevil resistance can be achieved without compromising grain yield
Effect of packaging methods on the storage stability of dried capelin under simulated temperature and humidity conditions
Get PDFSmall pelagic fish have grown in importance for the food and nutrition security of people indeveloping countries. The goal of this study was to improve the storage stability of dried smallpelagic fish (Capelin - Mallotus villosus) using appropriate packaging methods. Commerciallydried capelin was packaged using conventional air packaging (AP), vacuum packaging (VP),modified atmosphere packaging (MAP, 99.9% N2) and hessian bags (HB) before storage atsimulated temperature and humidity conditions of Uganda (relative humidity H” 54 and 83%;temperature H” 30 and 17 °C, respectively) for 8 weeks. Chemical and microbiological stabilityof the dried capelin was assessed with respect to packaging methods. Water content and wateractivity increased significantly (p<0.05) for the HB packed capelin (12.7 – 17.6% and 0.6 -0.7, respectively). Lipid content decreased significantly (p<0.05) towards the end of storage inthe HB packed dried capelin. Primary lipid oxidation (peroxide value) was lowest in the vacuumpacked dried capelin (31.5 – 53.5 ìmol kg-1). Secondary lipid oxidation (TBARS) decreasedsignificantly (p<0.05) with storage time in the modified atmosphere packed dried capelin(250.3 – 152.9 ìmol MDA kg-1). Free fatty acid content of dried capelin increased throughoutstorage irrespective of the packaging method. Total microbial count decreased significantly(p<0.05) in the vacuum packed dried capelin (4.8 – 3.6 log cfu g-1); while mould counts increasedsignificantly (p<0.05) in the HB packed dried capelin (1.0 – 3.0 log cfu g-1). VP and MAPenhanced the storage stability of dried Capelin
A bioeconomic analysis of the carbon sequestration potential of agroforestry systems: A case study of Grevillea robusta in South Western Uganda
Get PDFGrevillea robusta is an agroforestry tree species that has been widely promoted under the carbon forestry schemes in South Western Uganda. The objective of the study was to estimate the amount of carbon sequestered and the profitability of carbon offsets in G. robusta woodlot andagroforestry management options under the Plan Vivo system and small-scale Clean Development Mechanism (CDM). An allometric equation forG. robusta was used to calculate the carbon stocks and merchantable wood volume in the woodlot and agroforestry management options over different crediting periods. The results indicated that G. robusta woodlots and agroforestry management options sequestered 470 and 225 t CO2 e ha-1 respectively, over a 20 year rotation. The net present values (NPVs) of the G. robusta agroforestry management option of US1358 and 1902 ha-1 in the G. robusta woodlot management option. The NPV of the traditional agroforestry system was US$ 3992 ha-1. These results show that, whereas the woodlot option stores more carbon, it is the least profitable option. Analysis also revealed that, although poor households were well represented in the Plan Vivo scheme, they preferred the agroforestry option. This suggests that forest carbon offsets on productive agricultural land, should focus on promoting agroforestry technologies in order to increase profitability and targeting of the poor households
Comparison and suitability of genotype by environment analysis methods for yield-related traits of pearl millet
Get PDFPearl millet (Pennisetum glaucum (L.) R. Br.) is an important food security and income crop for households living in semi-arid zones in Uganda. However, the genotype by environment interaction, in addition to the several methods used for its assessment, complicates selection of varieties adapted to such semi-arid areas. The objective of this study, therefore, was to compare common methods used to assess stability and adaptability of improved genotypes. Seventy six genotypes were planted in four environments in an alpha experimental design with two replications. Results showed that genotype by environment interactions were significant at p<0.05 for grain yield, days to 50% flowering and 50% physiological maturity, percentage of productive tillers and panicle area. Results further showed inconsistency in ranking of genotypes between methods; although Cultivar Superiority, REML, Yield Stability Index and GGE biplot were consistently correlated and identified high yielding and stable genotypes
Efficacy of bio and synthetic pesticides against the American bollworm and their natural enemies on cotton
Get PDFCotton production in Uganda is limited by various factors among which insects pests are the most important. The key insect pests of cotton are the bollworm complex; spotted bollworm, Earias insulana; pink bollworm, Pectinophora gossypiella and American bollworm, Helicoverpa armigera. The American bollworm is an alien species and the most disastrous among all the three bollworm species attacking cotton in Uganda. Management for the bollworm complex in Uganda is largely synthetic chemical use with little or no biopesticide use which reduces natural enemies population and resistance development to continuous use of a single synthetic pesticide product. Therefore this study aimed at determining the efficacy of bio and synthetic pesticides on the management of cotton bollworm pests with special reference to the American bollworm. The pesticides in the study included Nimbecidine (Azaradactin), Engeo K247SC (Lambda Cyhalothrin 106 g l-1 + Thiamethoxam 141 g l-1), Talstar (Bifenthrin), and Amdoc3EC (Emamectin and Abamectin), Aster extreme 20SL (Acetamiprid 150g/l and Cypermethrin 50 g l-1), Agrolambacin (15 g l-1 Lambda Cyhalothrin + 300 g l-1 Profenofos), Thiodicarb (Larvin 80DF), and Methomyl (Lannate 40SP) on cotton bollworm (Helicoverpa amigera) and its natural enemies in eastern Uganda. The study was conducted at the National Semi-Arid Resources Research Institute (NaSARRI) under both laboratory and field conditions. Under laboratory controlled conditions, recommended doses of these bio and synthetic pesticides were used against third instar larvae of the American bollworm in a completely randomised experimental design with five replicates. Amdoc 3EC and Nimbecidine, showed maximum efficacy, 100 %, in terms of mortality after 72 hours. While Engeo, Aster extreme and Agrolambacin showed maximum mortality of (100%) after 96 hours followed by Larvin 80DF (80%) and Lannate 40SP (67%). In the field conditions, Nimbecidine (0.3 and 1.00) and Talstar (2.0 and 1.7) were the most effective bio-pesticides; while Amdoc with means (1.8 and 1.9), Aster extreme (2.0 and 1.8) and Agrolambacin (1.5 and 1.3) were the most effective synthetic pesticides respectively. Seed cotton yield was significantly higher in biopesticide treated plots, Talstar 1966 , 1935 kg ha-1, Nimbicidine 1985 and 1715 kg ha-1 compared to the synthetic pesticide treated plots with amdoc1935 and 1506 , Agrolambacin 1846 and 1722 kg ha-1 , Aster extreme 1733 and 1930 kg ha-1 respectively. Computation of the benefit cost ratios showed that these new chemical pesticides were all financially viable and, therefore, adoptable by the cotton farmers, respectively which also performed better than the controls 1012 and 912kg ha-1 outside the experiment, 892 and 602 kg ha-1 inside the experimental area. In addition, synthetic pesticide
Effectiveness and profitability of insecticide formulations used for managing snap bean pests
Get PDFSnap bean (Phaseolus vulgaris L.) farmers rely mostly on insecticides to manage pests and to satisfy the stringent market requirements for insect and blemish-free pods. However, the cost of these pesticides lowers farm incomes. In addition, heavy and wrong use of pesticides could result in residue accumulation, which reduces market access by the farmers. To identify optimal pest control with lower economic risks to farmers, we investigated the effectiveness and profitability of different insecticides and insecticide formulations against bean fly (Ophiomyia spp.) and bean flower thrips (Megalurothrips sjostedtii). Two separate experiments were conducted during 2009 to 2012. The first experiment targeted bean fly and bean flower thrips, comprising the treatments: seed dressings, soil drenches, foliar sprays and an untreated control. We used randomised complete block design, with four replicates. All the seed dressing and soil drenching insecticides, except Apron, significantly lowered bean fly infestation by two to 60 fold when compared with control. These insecticides, however, did not control flower thrips. Confidor® resulted in a marginal returns of 0.89 and Actara® -0.11 compared to seed dressings, which ranged from 0.47 to 1.82. The second experiment laid in a randomised complete block design involved the foliar application of Roket® under different spray regimes. Application of Roket® reduced infestation of thrips, and resulted in positive MRR in all the seasons
Nutritional and physicochemical properties of stored solar-dried cowpea leafy vegetables
Get PDFPreservation techniques for cowpea (Vigna unguiculata L.) leaves, a green leafy vegetable mainlyconsumed in the eastern and northern parts of Uganda, are still lacking. The study aimed atdetermining the effect of blanching, open sun and solar-drying on the nutrient content,organoleptic acceptability and physicochemical properties of cowpea leafy vegetables (CLV) duringstorage. Proximate composition, sensory quality and colour of the CLV were determined. Nosignificant differences (p < 0.05) in nutrient composition were observed between drying methods,except the dietary fibre, zinc and total carotenoid content. Blanched-solar dried CLV showedhigher dietary fibre and total carotenoid content compared to raw dried CLV. No significantdifferences (p > 0.05) in appearance, taste, flavour, and texture of dried CLV were observed, exceptfor the fresh CLV (control). Water activity levels ranged from 0.34 to 0.54 indicative of storagestability. Positive ‘L’ colour values (37.90 to 44.95) indicative of light green to green, negative ‘a’values (-7.28 to -4.15) for greenishness and positive ‘b’ values (3.45 to 9.25) for yellowishness forraw-dried and blanched green leafy cowpea vegetable, respectively, were obtained. Markedincreases in browning index and total colour difference were observed in the dried CLV duringstorage. Blanching and solar drying treatment formed stable and highly acceptable vegetablesduring storage, which could be recommended for market
Morphological variation of Nile tilapia populations from major water bodies of Uganda
Get PDFWith increasing demand for improved farmed Nile tilapia (Oreochromis niloticus) fish seed, thereis heightened demand for quality and proven broodstock by hatchery operators throughout thecountry and in the East African region. Uganda, fortunately, is endowed with vast natural Niletilapia (Oreochromis niloticus) stocks in lakes Albert, Edward and George, as well as in Albert NileRiver. To aquaculturally benefit from the different attributes of different stocks/strains, it isimportant to establish the existing strains in a manner that is phenotypically discernible wheresuch differences are apparent. In this study, we used a suite of morphological traits to identifystrains of Nile tilapia among 425 individuals sampled from the four major water bodies, lakes –Albert, Edward-George, Kyoga and Victoria. Morphological variation was investigated usingmultivariate approaches including principal component analysis, discriminant analysis andcluster analysis of 22 morphometric characters. These analyses indicated that there was highmorphological variation among the different populations of Nile tilapia and the fish could begrouped into their respective sampled areas based on these morphological differences. Most ofthe variation (86.97%) was associated with the fish body size, the peduncle length and the interorbital distances. Findings imply that there are four major Nile tilapia strains in Ugandan watersthat will be subjected to aquaculture performance evaluation before being used in the geneticimprovement programme to produce improved Nile tilapia fish broodstock/seed for use in fishfarming. Differences among populations may reflect genetic differences and/or environmentalfactors