One of the most important and revealing attributes of livestock is their live weight. This single measurement can help farmers effectively manage their stock and is critical for making informed decisions on aspects of animal production such as feed rations, market value, administration of veterinary drugs and mating times. For instance, without a proper estimate of an animal’s live body weight, there is a potential risk of either overdosing or underdosing a sick animal with veterinary drugs; with the former leading to wastage and potential health risks and the latter leading to ineffective disease control.

Live weight (LW) can also help farmers determine the nutritional condition of their animals, assess their growth rate and determine their breeding value. An animal’s weight is a reliable indicator of its overall condition if considered in relation to its age. The use of a well-calibrated weighing scale is one of the most common and direct ways of estimating livestock weight. But this method poses a challenge for small-scale livestock keepers because weighing scales are often expensive and costly to maintain. Only a few farmers can afford them. Weighing animals is also cumbersome and stressful for herds and many farmers and traders opt to rely on their visual judgement when estimating the weight of their animals, which is mostly based on experience and therefore prone to subjectivity.

Researchers from the Mazingira Centre at the International Livestock Research Institute (ILRI), have developed a mobile phone application (app) to help farmers better gauge the live weight of their animals. The “eWeigh” app is a free farm management resource tool, built around the use of a simple and accessible proxy measure i.e. the heart girth (HG) to estimate live weight. Studies have shown that an animal’s LW is closely related to its chest circumference. Using the heart (chest) girth measurement has been found to yield a reliable prediction of LW in cattle and other livestock species such as sheep and goats. This easy to perform measurement, used in conjunction with a set of tables (or equations), allows a farmer to estimate animals’ LW with some confidence, but here there have been problems. The LW/HG relationship is based on animal measurements and many published studies have used European breeds of cattle. When these equations are used, there tends to be higher errors in estimates. The second problem is the calculation itself, where farmers must either refer to tables, or perform manual calculations to get their animals’ LW.

Since the estimation of an animal’s LW from its HG measurements can be influenced by several factors including breed, sex, environment and production system; it is necessary to develop specific models (algorithms) for predicting LW, that are context- and region-specific, in order to increase the accuracy of LW estimations. The use of the HG measurement to estimate LW is a technique that has been used for over 70 years, with over 30 different algorithms developed for various populations of livestock around the world. The eWeigh app has been developed using an algorithm developed from an earlier study by Goopy et al., which is based on data from over 9,000 animal measurements in East Africa and West Africa. This means that the app is developed from the most robust and widely applicable algorithm possible, which is both easy to use and flexible for additions and other improvements.

The eWeigh app is available on the Android platform and can be downloaded and installed from the Google Play Store. Once installed by a farmer, this application only requires input of the animal identification or name (ID) and the HG measurement to give a LW estimate. The eWeigh app does the calculations for the farmer, making it easy and convenient to use.

To help make the most of the LW estimate, eWeigh offers farmers additional information such as basic ration formulation to meet production objectives (milk production or weight gain), correct dosages of veterinary chemicals and guidance on correct time for first mating. But note that this app does not replace the need for veterinarian services, especially in the administration of veterinary drugs and chemicals.

The eWeigh app was developed as part of a GIZ-funded project on ‘Training materials and tools for smallholder dairy farmers: towards achieving climate smart livestock’, which runs from December 2018 – March 2020 under the umbrella of the Green Innovation Centres for the Agriculture and Food Sector. The project has trained 227 farmers (35% female) in Kakamega, Siaya and Migori counties in Kenya on the use of the app. They were trained on downloading and installing the eWeigh app, creating farmer accounts, adding cattle to farmer accounts, and getting live weight after adding heart girth measurements. The farmers also learnt how to get appropriate feed rations for their cattle based on production goals, how to get drug dosages for various cattle diseases as well as knowing the timing for the first mating, based on an animal’s weight. The app was well received by the farmers, most of whom appreciated not having to perform calculations or refer to conversion tables. The LW values from the app were found to be within the same range as those derived from conversion tables that the farmers were using previously.

During the testing period for the app, it emerged that the principle of the HG measurement was not clearly understood by some farmers and this was addressed by providing additional training.

The data storage capability of the app is a major advantage. All data recorded by farmers is stored on a cloud-based database and can be easily retrieved. The app’s capabilities hold massive potential for expansion, which would allow it to be used in various locations. But moving to the next stage of using the app will require additional investment to either validate existing algorithms or develop new ones. Curation of information on the app, which is currently handled by ILRI, will also need dedicated staff and infrastructure.

The functionality of the app could be further expanded to provide services such as market information, management of herd records and animal census. The app could also be developed into a farmer-to-farmer trading platform – with the possibility of engaging commercial partners.

It is envisioned that eWeigh will go a long way in improving animal LW estimations in the region, thus allowing farmers to make well-informed decisions regarding their livestock. Plans are currently underway in Kenya and other countries to continue awareness-raising on the app, conduct training and get this must-have app in the hands of as many farmers as possible.

Read the study on simple and robust algorithms to estimate liveweight in African smallholder cattle