Phenomics

Development of wearable device-derived phenotypes to investigate genetic variation in heat tolerance in sheep

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Abstract

Historically, New Zealand has been regarded as having a temperate climate, and sheep production has largely relied on temperate-adapted breeds such as the Romney; however, climate change is driving increasingly sub-tropical conditions in several regions, elevating the risk of heat stress for livestock. In parallel, the use of shedding breeds has increased, although existing literature indicates that shedding alone does not confer heat tolerance, highlighting the need for breeding programmes to develop scalable phenotyping approaches capable of capturing behavioural and physiological responses to heat load. Sheep employ a range of mechanisms to cope with heat stress, traditionally measured through visual observation such as recording shade-seeking behaviour or manually counting respiration rate; while informative for small studies, these approaches are unsuitable for generating the large datasets required for genetic analyses. Wearable technologies offer a promising alternative by enabling high-resolution, continuous phenotyping, and this study reports the early-stage development of two wearable-derived heat tolerance phenotypes: shade-seeking behaviour quantified using GPS collars and respiration-rate estimation using jaw-mounted accelerometer sensors. A pilot GPS collar study was conducted on 112 ewe lambs sired by a mixture of temperate (Romney) and shedding (Wiltshire, Dorper, Damara and composite) sires, with data collected during the New Zealand summer of 2025 (January-February) at five-minute intervals. Analyses focused on a six-day period in early February when animals were exposed to variable Temperature-Humidity Index (THI) conditions, calculated using ambient air temperature expressed in degrees Celsius, and had consistent access to shade provided by a line of trees. Distance to shade or water was calculated and averaged within THI classes, revealing variation in proximity to shade as THI increased; across the dataset, the greatest average distance from shade occurred at THI 17 and declined almost linearly to THI 24, the highest THI observed. Although based on a limited dataset, preliminary between-sire differences were observed, with an estimated heritability of 0.71 ± 0.40 for shade-seeking behaviour at THI 17; given the large standard error and small sample size, this result should be interpreted cautiously but suggests that genetic variation in behavioural thresholds for heat avoidance may exist. In a separate dataset in which jaw-mounted accelerometers were fitted to lambs exposed to similar THI variation, accelerometer traces showed distinct waveform patterns during periods of elevated heat load that aligned with expected increases in respiration rate. Ongoing work aims to automate signal processing to generate longitudinal respiration-rate phenotypes aligned with GPS-derived behavioural data. The next phase of this research will involve deployment of wearable devices across larger numbers of sheep from diverse genetic backgrounds to enable robust estimation of genetic parameters and evaluation of the feasibility of incorporating heat tolerance traits into breeding objectives in New Zealand sheep.

Keywords: 2026

How to Cite:

Booker, F., Hitchman, S., Johnson, P. & Pickering, N., (2026) “Development of wearable device-derived phenotypes to investigate genetic variation in heat tolerance in sheep”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2287393. doi: https://doi.org/10.31274/wcgalp.24288

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