Abstract
Heat stress is one of the most important environmental stressors facing poultry production and welfare worldwide. The detrimental effects of heat stress on poultry range from reduced growth and egg production to impaired health. Animal vocalisations are associated with different animal responses and can be used as useful indicators of the state of animal welfare. It is already known that specific chicken vocalisations such as alarm, squawk, and gakel calls are correlated with stressful events, and therefore, could be used as stress indicators in poultry monitoring systems. In this study, we focused on developing a hen vocalisation detection method based on machine learning to assess their thermal comfort condition. For extraction of the vocalisations, nine source-filter theory related temporal and spectral features were chosen, and a support vector machine (SVM) based classifier was developed. As a result, the classification performance of the optimal SVM model was 95.1 ± 4.3% (the sensitivity parameter) and 97.6 ± 1.9% (the precision parameter). Based on the developed algorithm, the study illustrated that a significant correlation existed between specific vocalisations (alarm and squawk call) and thermal comfort indices (temperature-humidity index, THI) (alarm-THI, R = −0.414, P = 0.01; squawk-THI, R = 0.594, P = 0.01). This work represents the first step towards the further development of technology to monitor flock vocalisations with the intent of providing producers an additional tool to help them actively manage the welfare of their flock.
Highlights
Animal vocalisations are a fundamental component of animal behaviour, and can be used as useful indicators of the animal welfare state [1,2,3]
This study aims at developing a sound-based monitoring method to automatically evaluate laying hens’ thermal comfort through automated vocalisation detection
To obtain optimised parameters for the training support vector machine (SVM) model, the code: classification search parameters.vi was implemented on the LabVIEW software platform
Summary
Animal vocalisations are a fundamental component of animal behaviour, and can be used as useful indicators of the animal welfare state [1,2,3]. Heat stress is one of the most critical environmental stressors in poultry production worldwide [4]. The detrimental effects of heat stress on poultry range from reduced growth and egg production to decreased egg quality and safety [5,6]. High ambient temperatures have marked impacts on the behaviour, feed and water intake, heat production, and physiological responses (body temperature, respiratory rate and heart rate) of poultry [7,8], which might elicit specific vocalisation such as alarm, squawk, and gakel calls [9]. The gakel-call, as an indicator of frustration, can serve as an additional indicator of welfare in laying hens [10]. The number of gakel-calls and alarm-cackles can be regarded as potential indicators of frustration when recorded continuously [9].
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