Pictorial Evaluation Tools - PETs
PET- Livestock Methodology
1. PET- Livestock
1.0 The PET- Livestock protocol to score farm animals according to body condition, as represented by the layers of flesh cover at designated target areas of the body of each animal, comprises the structured application of increasing intensities of observation, best described diagrammatically as an inverted pyramid with high numbers observed from a distance, fewer animals observed in “close-up” detail, and a sample only discussed with the herders in case-studies, as shown in Figure 1.
Figure 1. Observation Levels
2. Vehicle Transects
2.1 At the first level, travelling at a slow, steady speed, observers score individual animal’s body condition on a scale of 1 to 5, as seen through the windshield of a vehicle. At such a distance and speed*, the designated target area of each of the animals’ bodies as seen as the observer approaches or passes through groups of livestock, is matched against one of the 5 PET approach photo-indicators and the group scored according to the mode i.e. the most frequently occurring score of individuals in the group. In such a way, at this level, individuals are observed but the herds and flocks are scored, collectively.
2.2 Every individual, herd or flock passed during the transect should be scored in such a manner, provided the individuals’ bodies are suitably aligned (see PET- Livestock manual), by marking scores given in tables under headings corresponding to the 5 scores for each species, with approximate numbers involved in each group. The scores are added-up with the estimated numbers in the groups scored, and at the end of the transect, weighted averages calculated for each species and for each area traversed.
3. Walking Transects
3.1 On arrival at a designated area, or, an area of specific interest as determined by the results of the initial observations, or at predefined regular intervals, observers leave the vehicle and switch to walking transects which enables them to observe animals much more closely. Different classes of animals may now be identified and scored accurately using the close-up, photo- indicators to differentiate between the scores of e.g. milking cows and dry cows; draught animals and slaughter stock, store sheep and goats and breeding females. In each case animals are scored individually and weighted averages calculated.
4. Case Studies
4.1 When sufficient sample herds and flocks have been closely observed and scored during the walking transect, the observation sequence is completed by conducting detailed case-studies of a sample of farmers/ herders involving semi-structured interviews about his/her livestock using a common pre-tested/ proven checklist relating to the inputs, setbacks and performance of the herds and flocks under detailed observation.
4.2 At the end of each day, each team or individual observer summarises the weighted returns for the vehicular and walking transects and prepares summary sheets from the completed interview check lists. Combining the two sources of information completes the rapid assessment of livestock in that particular location with the vehicular scores providing the general picture and the walking transects providing the scores for the different classes of stock.
4.3 PET- Livestock also contains photo-indicators for rangeland forages that may be used in accordance with the PET- Crops protocol to be found in the PET- Crops section of this website; and, a methodology for rapid estimation of browse tree and shrub densities in the ranges visited during transects called “point- to- plant”.
PET Methodology - further details
Emphasis during briefings was placed on the facts that:-
- PET is a tool for rapid assessment using Optimum Levels of Accuracy (OLA);
As such speed of application, analysis and reporting is essential. The general scores for each species will differ from specific scores of classes of stock within species, but the scores should relate to one another in a way that can be explained by information received during the cases studied;
The PET manual provides the formulae to be applied to assess condition and performance, but it is the rigour, consistency and stamina of the teams using the manual and associated methodology that makes the approach successful;
PET Livestock provides a means of estimating and explaining livestock body condition at the time of the mission, however, the true value of the process is identifying change in condition of the same herds and flocks in the same place over time and/or differences between different herds and flocks in different areas at the same time. Therefore, the timing and frequency of assessment missions applying PET needs careful consideration and planning to make best use of the system.
*To be determined by trial and error and depends on the eye and mental agility of observers and the weather.