Genetic control of immune responsiveness in the chicken

Disease can be combated by medication, vaccination, hygienic measures, eradication and genetic resistance. Genetic resistance to infectious diseases is advantageous because of its permanent character in contrast with the aforementioned procedures. In the chicken genetic resistance to specific diseases like Marek's disease and lymphoid leukosis is well known. Despite this knowledge improvement of genetic resistance to specific diseases is not included extensively in breeding programmes yet. The need for infection of populations, the lack of knowledge of correlations with resistance to other diseases and production traits and the rare understanding of defence mechanisms are major drawbacks for application.A different approach to genetic improvement of disease resistance is the composition of a series of defence traits, defining general resistance to disease. The major histocompatibility complex, the B-locus in the chicken, may be such a valuable marker especially for resistance to viral oncogenesis. The capacity to produce antibodies to a multideterminant antigen, like sheep red blood cells (SRBC) is another possible marker trait. Selective breeding for this trait in mice has shown, that the effects are non-specific. In this thesis genetic and environmental aspects of the agglutinin antibody response to SRBC in poultry are discussed.The agglutinin antibody response to SRBC was polygenically determined. Heritability estimates for total antibody titre and 2-mercapto-ethanol (2-ME) resistant and sensitive antibody titres varied from non-significant to, usually. levels around .2 to .3 for the primary response in White Leghorn (WL), White Plymouth Rock (WPR) and ISA Warren populations. The heritabilities of a secondary response, measured in WPR and ISA Warren populations, were somewhat lower. The size of these heritability estimates offers a good perspective for mass selection as already shown in the first selection generation for high and low antibody production in our ISA Warren population. Moreover the repeatibility of this trait is very high, above .9.Phenotypic correlations between primary and secondary total antibody titres were not significant in a OR population. This result was explained by a positive relationship between primary 2-ME sensitive antibody titres and secondary 2-ME resistant antibody titres and a negative relationship between primary and secondary 2-ME sensitive antibody titres. Additive genetic correlations between total antibody titres of primary and secondary response were quite negative. If these negative genetic correlations will be confirmed by other research workers, then the choice of the primary antibody response to SRBC as a selection criterion for general disease resistance becomes a major concern.Differences between three stocks: WL, WPR and ISA Warren were found for antibody response to three doses of SRBC and for the cell-mediated response, the swelling of the wingweb post phytohaemagglutinin (PHA) injection. Genetic origin by dose of SRBC interactions were absent. However the response curve was different for each stock, indicating genetic origin by testday post injection interactions. Phenotypic correlations between total antibody titres to SRBC and PHA wingweb swelling were absent, overall and within stocks.The antibody response to SRBC is influenced by many non-genetic factors. Important non-genetic effects were dose of SRBC, age of the chick, primary versus secondary response, vaccination programme, interval between SRBC injection and titre determination. Desirable traits of the defence system in combating infectious diseases are immune competence at an early age, responsiveness to low doses of infectious agents. a quick response post infection and development of memory. The selection criterion, therefore, has to be clearly defined and the effects of selection upon these desired characteristics will have to be evaluated.Considering the heritabilities, the repeatibility and the manifestation at an early age, the haemagglutinin antibody response to SRBC offers a perspective for selection. The value of this trait for general disease resistance will have to be proven in the near future, when our selection lines for high and low antibody responsiveness have been established

Farmers' perceptions about exotic multipurpose fodder trees and constraints to their adoption

Many organizations in Ethiopia have for many years promoted exotic multipurpose fodder trees (EMPFT) for livestock feed and soil improvement. Despite the apparent benefits, the number of farmers planting these trees was low. The objectives were to elucidate farmers¿ perceptions about their use value, management practices and constraints to adoption in three districts representing annual (one wheat-based and one teff-based) and perennial (coffee-based) crop-livestock systems in the Ethiopian highlands. Data were collected from 235 farm households. Most farmers (95.3%) had awareness of EMPFTs and the principal information sources were development agents (75.3%). Over half of the farmers were motivated to plant EMPFTs for feed value. Motivation for other purposes depended on cropping system, vegetation cover and availability of alternative local fodder trees in the area. Farmers had positive perceptions about EMPFTs for their feed value and contribution to soil conservation. Current adopters had a mean number of 587 (SE ± 84) EMPFTs per farm. Major constraints to adoption of EMPFTs were agronomic problems, low multipurpose value, and land shortage. Majority of farmers (89.8%) were interested to either continue or begin fodder tree development. Of the interested respondents, 44.5% preferred local fodder trees whereas 55.5% preferred EMPFTs. We conclude that farmers are aware of use values of EMPFTs while perceived constraints suggest that introduction of EMPFTs need consideration of farmers multiple criteria, but also awareness of feeding fodder trees and resource availability. Moreover, current development approaches have to recognize the importance of involving the end-users at all stages through participatory approaches to enhance adoptio

A Conceptual Framework to Assess Development of Smallholder Crop-cattle Farming Systems in Bhutan:Sustainable Development or Gross National Happiness?

The objective of this paper is to compare the concepts of Sustainable Development (SD) and Gross National Happiness (GNH) to assess development at various level, especially at the smallholder crop-cattle farming systems level in Bhutan. The concept of SD was conceived about two decades ago, while GNH is a development paradigm that drew international attention in 1998.In this paper the similarities and differences of the SD and GNH concepts and their application to the case in Bhutan are reviewed. The generally cited four pillars of GNH are proposed as “building blocks” of GNH. They are sustainable and equitable socio-economic development, ecological preservation, preservation and promotion of culture and good governance. A conceptual framework to assess context dependent issues of GNH is developed. It is concluded that GNH assessment may be more appropriate at higher systems levels (e.g. district, national level) since it is at these level that the “building blocks”of GNH constitutes a useful framework through which regional and national development can be actualized. At present, for farm level assessment SD could be more appropriate since the indicators for the “building blocks”of GNH such as culture and good governance are still very few, qualitative and rather vague.Article信州大学農学部紀要. 46(1-2): 123-137 (2010)departmental bulletin pape

Kip: het meest complexe stukje vlees : marktmechanismen, ketenrelaties en integrale duurzaamheid »

De structuur en de cultuur van de pluimveevleesketen en de afzonderlijke schakels zijn in deze rapportage onder de loep genomen. Tevens worden conclusies en aanbevelingen voor de pluimveevleesketen gepresenteerd, waarbij oplossingsrichtingen worden voorgesteld voor de problematiek waarmee de sector wordt geconfronteerd

Livestock intensification and use of natural resources in smallholder mixed farming systems

Bhutan aims to intensify livestock production not only to improve livelihoods of farming households and to meet the increasing demands of livestock products, but also to sustainably use natural resources. This paper assesses the impact and trends of livestock intensification on the use of Common Property Resources (CPR), and how this affects the cattle numbers that can be maintained and the nitrogen (N) and phosphorus (P) flows at the farm. Data on household, cropping and livestock activities were collected through interviewing 183 households in extensive, semi-intensive, intensive, and intensive peri-urban areas in the years 2000 and 2004. In the extensive and semi-intensive areas, CPR was the most important source of Total Digestible Nutrients (TDN) for cattle. In the intensive areas with a majority of crossbred cattle, the farmers relied less on CPR than in the other two areas, but still about one quarter of the TDN requirements were met by grazing CPR. Grazing in the CPR provided the highest proportion of NP inputs at farm level; without grazing on CPR all four areas would have had highly negative soil nutrient balances. Intensification of livestock production through crossbreeding has not resulted in major reductions in cattle numbers per farm, but it is contributing to reduced use of CPR by farmers. Intensification partly replaces farm nutrient flows from CPR with nutrient inputs through increased use of concentrates, conserved fodder, and fertilizers. More awareness of nutrient management is required among farmers coupled with more research on nutrient assessments

White Gold : Opportunities for Dairy Sector Development Collaboration in East Africa

A study of the dairy sector in six East African countries was followed by a dairy expert consultation in Uganda in April 2014. The objective of the initiative was to explore possibilities to improve coordination among development agencies, investors and other value chain stakeholders and governments, and for creating synergy within and between the different countries. This report describes outcomes of both study and consultation and is intended to serve as a reference document for all stakeholders. It includes recommendations and priority actions that should enable stakeholders to capitalize on the opportunities in the East African dairy sector and clarify the roles of various partners in this endeavour (donors, public sector, and private sector). Study and consultation were initiated by the Inter-Agency Donor Group (IADG) on pro-poor livestock research and development. Report CDI-14-00