Background

The cross-sectional retrospective approach has long been used to estimate livestock demographic parameters in traditional farming systems (the earliest document we found describing such approach goes back to 1975 although it was used prior to that, CIRAD-IEMVT, 1989). The approach is based on farmers’ interviews and their short- or long-term recall of the herds’ demography. Different field methods were designed for implementing quick diagnostics (e.g. Dumas, 1980; Peacock, 1983; CIRAD-IEMVT, 1988; Planchenault, 1992; Meyer et al., 1997; Bebe et al., 2003). Nevertheless, methods have been the subject of little standardization or documentation. This limits the proper usage of the approach and generates variability in protocols implemented in the field, which in turn makes for difficulties in comparing and interpreting results.

In that context, a retrospective method, namely 12MO (meaning “the twelve-month method”), was designed in collaboration with ILRI, ICRISAT, AGRHYMET and MRA Niger (Lesnoff et al., 2008) in a research project funded by DGCD-Belgium and located in Niger (PAD Project: “Improved livelihoods in the Sahel through the development and implementation of household level bio-economic decision support systems”). This method had the objective to estimate a large panel of annual demographic rates (e.g. reproduction, mortality, offtake and intake rates), while remaining simple enough to be easily implementable in the field and transferrable to local structures (NARS, technical services, NGOs, etc.). The 12MO methodology was then revisited and improved in several research projects leaded by CIRAD in West Africa.

General characteristics of 12MO and purposes

12MO focuses on ruminant livestock herds managed in small-holder farming systems. During the farmer’s interview, the enumerator’s role is to enumerate exhaustively the animals present in the herd at the date of survey, and then record all the demographic events (births, natural deaths, slaughtering, loans, purchases, etc.) that have occurred in the last twelve months.

As a consequence, the main purpose of 12MO is to evaluate short-term demographic impacts of human interventions (e.g. heath and feeding farming practices or genetic improvements) or of shocks (e.g. disease outbreak, drought or economic crises). The method was not designed to evaluate average herd productivities over long period of time. Nevertheless, the method can also provide smoothed estimates of abortion and parturition rates (see the regression method in Chapter 5).

12MO can only be used on herds of small or medium size. For practical feasibility reasons, the method does not apply to herds of several hundred animals. Furthermore, 12MO surveys are frequently restricted on the “reproductive herds”, i.e. the herds containing enough females to be able to renew by themselves. This can have consequences on the representativeness of the estimates (see Chapter 1).

Warning

Cross-sectional retrospective surveys, such as 12MO, have the advantages to be implementable in large areas and in all types of farming systems (even the nomadic ones) at the difference of herds’ follow-up surveys.

Nevertheless, due to biases arising from farmers’ recall (e.g. omission of animals or demographic events for taxes avoidance, cultural reasons or simple forgetfulness) and from approximations in the calculations of the demographic rates (Lesnoff, 2008; Lesnoff and Lancelot, 2009; Lesnoff, Submitted), it must be remembered that 12MO yields approximate results.

In addition, the reliability of the method is highly sensitive to the quality of the field work and the perspicacity of the enumerators. Intensive filed training and supervision are highly recommended to insure reliable data.

In any cases, the 12MO results must be considered cautiously. When possible, herds’ follow-up surveys (with or without animals’ identification) with regular fortnightly or monthly visits of enumerators should be preferred, particularly when the objective is to build a referential frame on demographic parameters.

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12MO materials

Contact

matthieu.lesnoff@cirad.fr