Panting scores as a measure of heat stress evaluation in sheep with access and with no access to shade

Abstract

The threat to sheep welfare of heat stress when pastured outdoors in the summer, particularly without access to shade, has been underinvestigated. This may be of importance not only in hot climates, but also during the summer months in cooler climates. This study considered whether, in the moderately warm conditions of a northern European summer, sheep will access shade of they have access to it, and if sheep with no access to shade in a northern European summer show behaviours indicative of poor welfare, including measures of panting scores and other indicators of heat stress. There were twelve sheep in each of the groups, the control group (NS) or the treatment group with the possibility to access shade (SH). Respiration rates and panting scores were recorded for each sheep in each group twice each day. Other behaviours were also recorded at the individual animal level. In the SH group, the numbers of sheep in the shaded areas were also noted. Climatic data on observation days was collected. Respiration rates were significantly higher at higher panting scores (p < 0.001). Higher panting scores were recorded for NS sheep than for SH sheep (p < 0.001), as were breath intensities (p < 0.001). The behaviour of open mouth with tongue extended was not observed in the SH group but was observed in the NS group. SH sheep ruminated more (p = 0.011) than the NS sheep, while NS sheep stood panting more than the SH sheep (p = 0.001). Indicators of heat stress, respiration rates and panting scores, were more strongly correlated to air temperature and weather conditions in the NS group compared to the SH group, and these were significant. The number of animals observed to be in the shade in the SH group was positively correlated with air temperature. Panting score can therefore be used as a reliable measure for estimating respiration rate and heat stress in sheep. Sheep, even in northern Europe, can suffer from heat stress, particularly when given no access to shade, and shade from the sun should be provided for sheep at pasture.