Effects of shade on the behaviour and physiology of sheep in a temperate climate

• Published in: Applied animal behaviour science 2024-03, Vol.272, p.106185, Article 106185
• Main Authors: Schütz, K.E., Saunders, L.-R., Huddart, F.J., Watson, T., Latimer, B., Cox, N.R.
• Format: Article
• Language: English
• Subjects: air temperature; animal behavior; Behaviour; blood; blood sampling; cell respiration; cross-over studies; crossbreds; Heat stress; New Zealand; physiology; Respiration rate; Romney; Shade; Sheep; solar radiation; summer; temperate zones; thyroxine; tongue
• ISSN: 0168-1591; 1872-9045
• DOI: 10.1016/j.applanim.2024.106185

Heat stress negatively affects the welfare and production of sheep, particularly in warm climates. Less is known about heat stress and shade requirements of sheep in temperate climates. This study aimed to investigate behavioural and physiological responses of sheep with or without access to shade in summer in New Zealand, which has a predominantly temperate climate. Forty-eight mixed age Romney crossbreed ewes were managed in 4 groups in either shaded (2 m2 shade/sheep) or unshaded paddocks in a cross-over design (7 days/treatment). A blood sample was obtained before treatments commenced, at the cross-over, and after the second treatment (3 times/sheep) for analyses of red and white blood cells, non-esterified fatty acids (NEFA) and Thyroxine (T4). Lying behaviour was recorded continuously using HOBO accelerometers. Shade use, grazing, ruminating, lying, panting and drinking behaviour were recorded for 5 days/treatment using 10-min instantaneous scan sampling between 0900 and 1700 h. Individual respiration rates were obtained 2 times/h during the observation period. Weather was monitored using portable weather stations (mean air temperature was 19.8°C, range: 18.3–23.3°C). Sheep with access to shade were observed using the resource in 25.7% of observations and shade use increased with solar radiation. Unshaded sheep tended to spend more time grazing during the daytime, compared to when shaded (62.6 vs 57.7% of observations, SED=11.92, P=0.080). Both treatment groups were observed ruminating in similar percentage of observations (shaded: 25.5%, unshaded: 22.7% of observations, SED=6.22, P=0.227). Unshaded sheep spent 30.6% of the daytime observations lying down compared to 35.1% for shaded sheep (SED=6.05, P=0.055), however, lying times over 24 h were similar; shaded sheep spent, on average, 12.3 h lying down/24 h compared to 11.8 h for unshaded sheep (SED=0.36, P=0.258). Open mouth panting and tongue out were predominantly observed in unshaded sheep (open mouth: 0.61 vs 0.02%; tongue out: 0.25 vs 0.01% of observations for unshaded and shaded sheep, respectively), however, there were too few observations of these behaviours to be statistically analysed. Unshaded sheep had numerically higher respiration rates than unshaded sheep (130 vs 156 breaths/min, SED=28.5, P=0.410). Average respiration rate was >200 breaths/min on 3 and 7 days for shaded and unshaded animals, respectively. Only sheep without shade had daily average respiration rates ≥300 breaths/min.