A panting score index for sheep

• Published in: International journal of biometeorology 2019-07, Vol.63 (7), p.973-978
• Main Authors: Lees, A. M., Sullivan, M. L., Olm, J. C. W., Cawdell-Smith, A. J., Gaughan, J. B.
• Format: Article
• Language: English
• Subjects: Ambient temperature; Animal Physiology; Beef cattle; Biological and Medical Physics; Biophysics; Bovidae; Cattle; Climate control; Climatic conditions; Correlation analysis; Correlation coefficient; Correlation coefficients; Data processing; Earth and Environmental Science; Environment; Environmental Health; Heat; Heat treatment; Meteorology; Original Paper; Ovis aries; Plant Physiology; Posture; Relative humidity; Respiration; Sheep; Thermoregulatory behavior
• ISSN: 0020-7128; 1432-1254
• DOI: 10.1007/s00484-019-01711-3

When exposed to hot conditions, heat dissipation via an increase in respiration rate (RR) is an important thermoregulatory mechanism for sheep. However, evaluating RR under field conditions is difficult. In cattle, a viable alternative has been to assess panting score (PS); therefore, the objective of this study was to evaluate the relationship between RR and PS to determine if a PS index can be used to evaluate heat load in sheep. One hundred and forty-four Merino wethers (44.02 ± 0.32 kg) were used within a climate-controlled study. The study was replicated twice over 29 days, where each replicate consisted of two treatments: (1) thermoneutral (TN) and (2) hot (HOT). Ambient temperature ( T A ) and relative humidity (RH) were maintained between 18 and 20 °C and 60 and 70% respectively for the TN treatment. For the HOT treatment, heat load increased steadily over the 29 days. Minimum T A was 22.5 °C and maximum was 38.5 °C, while RH decreased (60 to 30%) as T A increased in the HOT treatment. A comprehensive PS classification was developed by enhancing the current sheep PS index and aligning the descriptors with the current PS index utilized in beef cattle studies. Respiration rate and PS were obtained for each animal at 3-h intervals between 0800 h and 1700 h daily. These data were used to determine the mean RR for each PS, across the study and within the TN and HOT treatments. The relationship between PS and RR was evaluated using a Pearson’s correlation coefficient. Data were also analyzed using a general linear model to determine the impact of PS, posture and animal identification (animal ID) on RR within each PS. Unsurprisingly, RR increased as PS increased, and PS, 0 and RR, 2.5 were 30.7 ± 0.59 and 246.8 ± 12.20 bpm respectively. There was a strong relationship between RR and PS ( r  = 0.71; P