Reliability of a Twelve-Month Retrospective Survey Method for Estimating Parturition and Mortality Rates in a Traditional African Livestock Farming System

Parturition and mortality annual rates are basic data for quantifying productivity of livestock populations in tropical extensive farming systems (14, 18, 23, 26). These parameters are estimated from data collected in the field. In developing countries, collecting data is a difficult task due to the dispersion and mobility of the herds and the fact that farmers do not keep written records about their herds. Herd monitoring with ear-tagged animals and periodic visits of trained surveyors are a gold standard (12, 35). Alternatives are cross-sectional retrospective surveys, based on farmers’ interviews and their shortor long-term recall of the herds’ demography (4, 14, 26, 31, 34). Retrospective surveys have been used for a long time (the earliest document found by the author describing the retrospective approach dates back to 1975 although the approach was used before that; 5) and in many contexts (2, 7, 27, 29, 30, 32). Their attractiveness may be related to their ability to implement quick diagnoses, and to be less cumbersome than herd monitoring and more suitable for surveying nomadic herds or large areas.