Introduction

Abstract

In traditional tropical low-input farming systems, livestock demographic parameters (e.g. reproduction or mortality rates) are important indicators for estimating and modelling herds’ dynamics and production. They synthesize two drivers of herds’ performances: the biological characteristics of the animals and the farmers’ herd management practices [1, 2]. Depending on the studies, demographic parameters can be considered as final variables of interest [3, 4] or intermediate input parameters of more global models (e.g. herd growth models). They have been extensively described in the literature on tropical livestock [5–11]. Nevertheless, in most cases, descriptions only rely on empirical presentations of formulas without clear methodological justifications. In that context, the first objective of the present handbook is to detail the theory behind the calculation of a set of demographic parameters (see [12] for an introduction in French). These parameters are defined based on a discrete-time framework where data are aggregated by period of time (year, month, etc.) and age class, in addition to other potential categories (species, breed, sex, etc.). In particular, the handbook presents important concepts used in demography, such as probabilities and hazard rates of occurrences and competing risks. Continuous-time methods for estimating demographic rates (e.g. the Cox model and extensions [13]) are well-known alternatives to discrete-time approaches. They have not been addressed in the handbook.