Ruminant livestock (cattle, small ruminants, and camels) have a determinant economic role in many tropical developing countries. In traditional low-input farming systems, demographic parameters (e.g. reproduction or mortality rates) are important indicators for estimating and modelling herd dynamics and production, and impacts of farming practices or environmental risks (droughts, epizootics, etc.). Although such parameters have been extensively described in the literature on tropical livestock, many descriptions only rely on empirical presentations of formulas without clear methodological justifications. This book fills this gap, presenting the main concepts used to define and compute demographic parameters for tropical livestock, such as probabilities and hazard rates of occurrences and competing risks. It is based on the LASER software, a relational database management system specifically designed for animal-based monitoring surveys. It also provides an introduction on R, the free statistical software (http://www.r-project.org) used for the computations.

It is intended for researchers, engineers, technicians, or students dealing with demographic parameters of tropical ruminant livestock in various fields such as animal science, epidemiology, or economy. It will also be valuable for readers wishing to enhance their understanding of definitions and formulas found in the literature, and it will guide them in their applications.

Auteur

Matthieu Lesnoff is a biometrician at CIRAD. He specializes in modelling tropical livestock demography.

Renaud Lancelot is an epidemiologist at CIRAD, with extensive field experience in Africa. He currently coordinates the European EDENext research project on vector-borne diseases.

Charles-Henri Moulin is an animal scientist and professor at Montpellier SupAgro. He specializes in livestock farming systems analysis in Mediterranean (France, Morocco) and tropical (Senegal, Mali, Brazil) areas.

Samir Messad is a biometrician at CIRAD with long experience in tropical livestock data management and analysis.

Xavier Juanès is a computer scientist at CIRAD. He has developed the LASER software and many other information systems for managing tropical livestock data.

Christian Sahut is a computer scientist at CIRAD, specializing in Web platform development.

Résumé
Having indicators to assess the effect of zootechnical, sanitary, economic or political intervention or the impact of environmental risks makes it possible to draw up strategies for improving domestic animal populations. This handbook is a compilation of the main concepts relating to the definition and calculation of demographic rates for largely non-intensive tropical animal farms. It is intended to be educational, and should help students, technicians, engineers, researchers and development staff to understand the definitions and formulas encountered in the literature more clearly and make them more self-sufficient in terms of analyses.

Contenu

Introduction.- 1.1. Background and objectives.- 1.2. Animal-based monitoring.- 1.3. A selection of parameters.- 1.4. Organization of the handbook.- 2. Grouping demographic data.- 2.1. Cohort splitting.- 2.2. Pseudo-cohort splitting.- 3. Mortality and offtake rates.- 3.1. One type of removal.- 3.2. Case with two types of removal.- 3.3. Additional points.- 4. Other demographic rates.- 4.1. Reproduction rates.- 4.2. Synthetic rates.- 4.3. Global demographic rates.- 5. Package laserdemog.- 5.1. R software.- 5.2. Functions in laserdemog.- 5.3. Additional points.- 6. Numerical examples.- 6.1. Example 1 Overall description.- 6.2. Example 2 More on reproduction rates.- 6.3. Example 3 Test of a treatment on mortality.- 7. Annexes.- 7.1. Rates p and h in survival analyses.- 7.2. R materials.- 7.3. Structure of tables generated by hsplit and vsplit.- 8. Bibliography.