Modelling the lactation curve of dairy cows using the differentials of growth functions

Descriptions of entire lactations were investigated using six mathematical equations. comprising the differentials of four growth functions (logistic. Gompertz, Schumacher and Morgan) and two other equations (Wood and Dijkstra). The data contained monthly milk yield records from 70 first, 70 second and 75 third parity Iranian Holstein cows. Indicators of fit were model behavior, statistical evaluation and biologically meaningful parameter estimates and lactation features. Analysis of variance with equation, parity and their interaction as factors and with cows as replicates was performed to compare goodness of fit of the equations. The interaction of equation and parity was not significant for any statistics, which showed that there vas no tendency For one equation to fit a given parity better than other equations. Although model behaviour analysis showed better performance of growth functions than the Wood and Dijkstra equations in filling the individual lactation curves, statistical evaluation revealed that there was no significant difference between file goodness of fit of the different equations. Evaluation of lactation features showed that the Dijkstra equation was able to estimate the initial milk yield and peak yield more accurately than the other equations. Overall evaluation of the different equations demonstrated the potential of the differentials of simple empirical growth functions used in file Current study as equations for fitting monthly milk records of Holstein dairy cattle

The use of simple sequence repeats markers to study genetic diversity in maize genotypes resistant to gray leaf spot disease

Genetic diversity in maize (Zea mays L.) is an important tool for progress in selection for traits of interest. The objective of this study was to screen genotypes for presence of markers linked to plantdefense against fungal diseases, and to study the genetic diversity in gray leaf spot resistant maize genotypes. Forty-one genotypes comprising of collections from Kenya, International Maize and WheatImprovement Centre, the International Institute for Tropical Agriculture and South Africa were identified to be resistant to gray leaf spot in Kenya in 2004. The genotypes were analyzed for variability by usingtwenty-eight microsatellite markers covering the entire maize genome. The results indicated diversity among lines for selected markers. Based on the diversity tree, ten clusters were observed. All genotypes occurred in clusters, except for genotypes EC573- (R12) C8S3-14-1, REGN 99/6, H623 and VHCY. The data indicated that, at least one line in each cluster showed a relationship in a locus with a corresponding parent. Occurrence of related lines also implied that there were common alleles that could have contributed to the gray leaf spot resistance

Determinants of contract farming for smallholder sunflower producers in northern Uganda

Contract farming is a form of vertical coordination, largely aimed at correcting market failures associated with spot markets that arise due to imperfect information. The objective of this study was to assess the determinants of farmer engagement in sunflower ( Helianthus annus L.) contracts in northern Uganda. Stratified random sampling was used to select 150 contracted and 150 non-contracted sunflower farmers in Oyam District, from where primary data were collected using a semi-structured questionnaire. A Logistic regression model was used to examine the factors that influenced farmer participation in contract farming. The major determinants of participation in contract farming by smallholder farmers were age (P<0.1), sunflower production experience (P<0.01), access to credit (P<0.01) and unit produce price (P<0.01).Collaborative efforts by all parties engaged in contracting arrangements are necessary to negotiate a minimum price with the farmers, with a possibility to re-negotiate whenever the market price is above the set price. The study pointed out that improvement in rural roads to enhance transportation of produce to mini-store is vital in driving sunflower contract farming in Oyam district. Therefore, policies aimed at improving rural roads are urgently needed.L\u2019agriculture contractuelle est une forme de coordination verticale, qui vise principalement \ue0 corriger les d\ue9faillances du march\ue9 associ\ue9es aux march\ue9s qui surviennent avec d\u2019informations imparfaites. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer les d\ue9terminants de l\u2019engagement des agriculteurs dans les contrats de tournesol ( Helianthus annus L.) dans le Nord de l\u2019Ouganda. Un \ue9chantillonnage al\ue9atoire stratifi\ue9 a \ue9t\ue9 utilis\ue9 pour s\ue9lectionner 150 cultivateurs de tournesol sous contrat et 150 sans contrat dans le district d\u2019Oyam, \ue0 partir desquels les donn\ue9es primaires ont \ue9t\ue9 collect\ue9es \ue0 l\u2019aide d\u2019un questionnaire semi-structur\ue9. Un mod\ue8le de r\ue9gression logistique a \ue9t\ue9 utilis\ue9 pour examiner les facteurs qui ont influenc\ue9 la participation des agriculteurs \ue0 l\u2019agriculture contractuelle. Les d\ue9terminants principaux de la participation \ue0 l\u2019agriculture contractuelle des petits exploitants agricoles \ue9taient l\u2019\ue2ge (P <0,1), l\u2019exp\ue9rience de production de tournesol (P <0,01), l\u2019acc\ue8s au cr\ue9dit (P <0,01) et le prix unitaire des produits (P <0,01). Les parties engag\ue9es dans des accords contractuels sont n\ue9cessaires pour n\ue9gocier un prix minimum avec les agriculteurs, avec la possibilit\ue9 de ren\ue9gocier chaque fois que le prix du march\ue9 est sup\ue9rieur au prix fix\ue9. L\u2019\ue9tude a soulign\ue9 que l\u2019am\ue9lioration des routes rurales pour am\ue9liorer le transport des produits vers les mini-magasins est essentielle pour stimuler l\u2019agriculture contractuelle de tournesol dans le district d\u2019Oyam. Par cons\ue9quent, des politiques visant \ue0 am\ue9liorer les routes rurales sont n\ue9cessaires de toute urgence

Farmers' awareness and application of banana Xanthomonas wilt control options: The case of Uganda and Kenya

Banana is a key staple and cash crop in east and central Africa. However, the recent outbreak of Banana Xanthomonas wilt (BXW) has threatened farmers whose livelihoods depend on the crop. Since 2002, stakeholders embarked on campaigns to sensitize farmers on the disease and its management. This study evaluated the effectiveness of these efforts by examining farmers' awareness of the disease, control options and their application in Uganda and Kenya. Data on BXW distribution and incidence, farmers' awareness of symptoms, mechanisms of spread and control options of the disease and banana production were collected through household surveys conducted in 2010. The results indicated that most farmers (> 90%) were aware of the disease and its symptoms and more than 50% were aware of the recommended control measures. Farmers obtained information on the disease from multiple sources but farmer-to-farmer interaction was the main source suggesting the key role rural social networks play in managing the disease. Not all affected farmers were able to apply control measures due to cost of intervention, lack of labour and inputs. The study recommends strengthening of linkages among stakeholders for better coordination of efforts and participatory development and promotion of farmer-oriented interventions that address farmer constraints

Structural basis for the high specificity of a Trypanosoma congolense immunoassay targeting glycosomal aldolase

Background : Animal African trypanosomosis (AAT) is a neglected tropical disease which imposes a heavy burden on the livestock industry in Sub-Saharan Africa. Its causative agents are Trypanosoma parasites, with T. congolense and T. vivax being responsible for the majority of the cases. Recently, we identified a Nanobody (Nb474) that was employed to develop a homologous sandwich ELISA targeting T. congolense fructose-1,6-bisphosphate aldolase (TcoALD). Despite the high sequence identity between trypanosomatid aldolases, the Nb474-based immunoassay is highly specific for T. congolense detection. The results presented in this paper yield insights into the molecular principles underlying the assay's high specificity. Methodology/Principal findings : The structure of the Nb474-TcoALD complex was determined via X-ray crystallography. Together with analytical gel filtration, the structure reveals that a single TcoALD tetramer contains four binding sites for Nb474. Through a comparison with the crystal structures of two other trypanosomatid aldolases, TcoALD residues Ala77 and Leu106 were identified as hot spots for specificity. Via ELISA and surface plasmon resonance (SPR), we demonstrate that mutation of these residues does not abolish TcoALD recognition by Nb474, but does lead to a lack of detection in the Nb474-based homologous sandwich immunoassay. Conclusions/Significance : The results show that the high specificity of the Nb474-based immunoassay is not determined by the initial recognition event between Nb474 and TcoALD, but rather by its homologous sandwich design. This (i) provides insights into the optimal set-up of the assay, (ii) may be of great significance for field applications as it could explain the potential detection escape of certain T. congolense strains, and (iii) may be of general interest to those developing similar assays