Breeding for trypanotolerance in African cattle

Trypanosomosis, or sleeping sickness, is one of the most important livestock diseases in Africa. Some West African cattle breeds show a degree of resistance to a trypanosome infection: they are trypanotolerant. At the International Livestock Research Institute (ILRI) in Nairobi, Kenya, an F2 experiment has been established to unravel the genetic background of trypanotolerance. This thesis had two main aims: First to determine the genetic background of trypanotolerance, and second to investigate opportunities to incorporate this information in a breeding scheme to increase performance of cattle in tsetse-infested areas. Based on the results from the F2 experiment, several traits were defined, which reflected features of trypanotolerant cattle. Subsequently, based on preliminary results from an analysis to determine chromosome fractions containing genes (QTL) involved in trypanotolerance performed at ILRI, the mode of expression of these QTL was investigated and one of the QTL was found to be maternally imprinted. These QTL could be utilised in an introgression scheme, but also for within breed selection. Both options were investigated. When introgressing QTL for disease resistance the optimal number of backcross generations from genetic or economic point of view was found to be different. The number of animals required is increasing very rapidly with increasing number of QTL to be introgressed. Within breed selection to increase production under constant infection pressure can be applied with or without aid of QTL for disease resistance. Mass selection on production under infection can be applied if no QTL information is available. A non-linear selection response is achieved in both potential production and disease resistance. Important advantage of QTL information for disease resistance is that animals can be selected outside the infected environment. In implementing a breeding scheme it is important to take into account that social-economic values and environments are very different in large parts of Africa as compared to Western countries. This thesis has demonstrated that there are good opportunities for using selection to improve the results of local farming systems.</p

Morphological features of indigenous chicken populations of Ethiopia

This study describes the variations in the physical features and the useful attributes of different populations of indigenous chickens. Five populations of chickens in different regions of Ethiopia were studied based on 13 qualitative traits recorded for a total of 1 125 chickens. Additional measurements on quantitative traits (shank length and body weight) were also included. Descriptive statistics (nonparametric and F tests) were used to analyze the data. Each of the study populations possessed multiple variants of plumage colours and other physical features. However, white body plumage is one of the prominent features of Farta chickens and red is predominant in the other populations. Pea comb is the dominant comb type in all regions. Most of the chickens in the high altitude regions have yellow skin. The geographic distribution and frequency of naked neck chickens are generally small, and the available small proportion is found mainly in the low altitude regions. Males in all populations are heavier and taller than the females. Body weights range from 1 411 g (Konso) to 1 700 g (Horro) in adult males and from 1 011 g (Konso) to 1 517 g (Sheka) in females. Most of the morphological traits that were studied showed a very low level of associations with each other

A running breeding program for indigenous chickens in Ethiopia: Evaluation of success

In 2008 a breeding program to increase production level in indigenous chickens was initiated at the Debre Zeit Agricultural Research Center in Ethiopia and is currently producing its 8th generation. Aim of this paper was to evaluate the success of the breeding program. Selection was on own performance for bodyweight at 16 weeks of age (BW16) and for the hens also on cumulative egg number at week 45 of laying (EN45). Heritability for BW16 in the 6th generation (G6) was 0.37, and for EN24 was 0.32. Phenotypic correlation between BW16 and EN24 was 0.36, but genetic correlation was -0.12. Genetic correlations of BW16 with cumulative egg production earlier in the laying series were 0.51 at 8 weeks of laying, decreasing to 0.22 at 16 weeks of laying. The genetic trends were positive for both traits under selection from generation 4 (G4) and G6

Gentechnologie bij landbouwhuisdieren

Een overzicht van de ontwikkelingen van het kloneren van landbouwhuisdieren, met het oog op mogelijke consequenties voor beleid en regelgeving. Er wordt ingegaan op de techniek van dna modificatie, de invloed op veehouderij, fokkerij, praktijk, dierenwelzijn en -gezondheid, nationale veiligheid en regelgeving en de toekomstige ontwikkelingen in de nabije toekoms

A resource allocation model describing consequences of artificial selection under metabolic stress

Long-term selection on production results in increased environmental sensitivity. This often is expressed through decreased fertility and increased health problems. The phenomenon has been described in all common farm animal species. One theory is that potential resource intake is insufficient to express production potential. Additional resources are drawn away from fitness-related traits, such as fertility and health, to further increase observed production. In addition, resources for maintaining fitness depend on the demands by the environment. In a harsh environment, more resources are required for fitness-related traits than in an optimal environment. Literature results show that selection in an optimal environment will increase sensitivity to less optimal environments. The objectives of this paper were to increase understanding of the underlying mechanism behind the development of environmental sensitivity and to gain insight into correlated response(s) when selection is on observed production. A resource allocation model was defined where observed production depended on production potential, resource intake potential, and the allocation of resources to production or fitness, including maintenance, health, and reproduction. Penalties for reproductive performance and probability of survival were included when the proportion of resources assigned to fitness dropped below a certain, environment-related, threshold. Mass selection was practiced on observed production during 40 generations using stochastic simulation. Depending on the heritabilities of the underlying components and on the environment, selection on observed production resulted in a decrease in reproductive rate and in the development of environmental sensitivity when resource intake becomes limiting. Correlations of observed production with underlying components changed across generations, following a nonlinear pattern. The proposed model is simple, but increases the understanding of underlying mechanisms and consequences of selection for production when resources are limiting

Modelling of resource allocation patterns

This chapter provides an introduction to the modelling of resource allocation as a way to generate insights and to make predictions. Resource allocation models provide a framework for considering genotype × environment interactions in animal production

Cría y Mejoramiento Genético Animal

ÍNDICE DE CAPÍTULOS (1° PARTE, CAPÍTULOS 1 A 7) • Capítulo 1: Introducción al mejoramiento genético animal • Capítulo 2: Conceptos básicos de la cría y mejoramiento de animales • Capítulo 3: Las razones para mantener a los animales determinan el objetivo de la cría y mejoramiento genético • Capítulo 4: La recopilación de información para la toma de decisiones • Capítulo 5: Los Modelos Genéticos • Capítulo 6: La diversidad genética y la endogamia • Capítulo 7: La herencia de rasgos monogénico

De meest efficiënte kip ter wereld : De Nederlandse legkippenfokkerij in de twintigste eeuw

This paper analyses the development of chicken breeding for eggs in the Netherlands in the twentieth century. The Dutch poultry sector was of only marginal significance early in the century, yet after the Second World War it developed into the most industrialised segment of animal husbandry. The introduction of scientific breeding methods played a central role in this, as well as the increasing dominance of specialised commercial breeding companies. While scientists and agricultural engineers developed several innovative approaches to breeding that helped increase egg production significantly, we argue that the methods on which these approaches were based – inbreeding, hybridising, selection and progeny testing – had been used by animal breeders since the eighteenth century. Scientists succeeded in increasing the efficiency of these methods by introducing the quantitative and statistical instruments of quantitative genetics; the new Mendelian theory was of little practical use in this respect. Hybrid breeding methods were also shaped by the commercial interests of breeding companies. In the Netherlands the rise of the poultry industry was slowed down for several decades by the government’s policy to protect the interest of smallholders, yet after the establishment of the EEC this protectionism was dispensed with. As an example of the role of commercial companies we discuss the early history of Hendrix Genetics, a Dutch-based breeding company that is now one of the two multinational enterprises that dominate the breeding market for egg-laying chicken worldwide