Influence of the Environment on Body Temperature of Racing Greyhounds

Abstract

Heat strain is a potential risk factor for racing greyhounds in hot climates. However, there have been limited studies into the incidence of heat strain (when excess heat causes physiological or pathological effects) in racing greyhounds. The aim of this study was to determine if heat strain occurs in racing greyhounds, and, if so, whether environmental factors (e.g., ambient temperature and relative humidity) or dog-related factors (e.g., sex, bodyweight, color) are associated with the risk of heat strain. A total of 229 greyhounds were included in over 46 race meetings and seven different race venues in South Australia, Australia. Rectal temperatures of dogs were measured pre- and postrace and urine samples collected for analysis of myoglobinuria. Ambient temperature at race times ranged between 11.0 and 40.8°C and relative humidity ranged from 17 to 92%. There was a mean increase in greyhound rectal temperature of 2.1°C (range 1.1–3.1°C). A small but significant association was present between ambient temperature and increase in rectal temperature (r2 = 0.033, P = 0.007). The mean ambient temperature at race time, of dogs with postrace rectal temperature of or exceeding 41.5°C, was significantly greater than at race time of dogs with a postrace rectal temperature ≤41.5°C (31.2 vs. 27.3°C, respectively, P = 0.004). When the ambient temperature reached 38oC, over one-third (39%) of dogs had a rectal temperature >41.5°C. Over half of postrace urine samples were positive by Dipstick reading for hemoglobin/myoglobin, and of 77 urine samples positive for Dipstick readings, 95% were positive for myoglobin. However, urinary myoglobin levels were not associated with ambient temperature or postrace rectal temperatures. The mean increase in rectal temperature was greater in dark (black, blue, brindle) than light (fawn and white) colored greyhounds. The results suggest heat strain occurs in racing greyhounds, evidenced by postrace rectal temperatures over 41.5°C and postrace myoglobinuria. Risk of heat strain may be increased in higher ambient temperatures and in darker colored greyhounds. Further research into the incidence of heat strain in racing greyhounds, and longer term physiological responses to heat strain, are warranted.

The effect of light vs dark coat color on thermal status in Labrador Retriever dogs

“…Future work should include studies with a longer cooling period to determine that time frame necessary for non-conditioned dogs to achieve baseline thermal status following thermal stress. The data presented here are inconsistent with the previous study examining racing greyhounds with larger proportions of dark coated dogs having higher rectal temperatures after racing [5]. Key differences between this study and the prior study on Greyhounds include controlled coat color (black or yellow vs. multiple light or dark colors), tighter grouping of age and sex, and a controlled time period and consistent environment.…”

“…These males were significantly larger in size than their female cohorts, so it is not known if sex or size played a role in their results. In addition, the darker colored group (n = 166) had more than twice the number of the light coated group (n = 63) which may have impacted the outcome [5]. In another study using Newfoundland dogs, researchers tested patches of white and black fur exposed to heat lamps.…”

Heatstroke – providing evidence-based advice to dog owners

“…Male racing greyhounds have also demonstrated significantly greater postrace rectal temperatures than female dogs, despite pre-race temperatures being the same in both genders (McNicholl, Howarth and& Hazel, 2016). Greyhounds with darker coloured coats, also showed a significantly greater increased in temperature post-race, than dogs with lighter coloured coats.…”

“…Figure 7. Cooling mechanisms that can be used in the field (Insert Figure 5 near here) The use of "cooling jackets" as a method of cooling dogs with heat illness cannot currently be recommended, as the only published data evaluating their use demonstrated a higher postrace rectal temperature in racing Greyhounds wearing cooling jackets immediately post-race, compared to those not using the jackets (McNicholl et al, 2016).…”

Changes in Pulse Rate, Respiratory Rate and Rectal Temperature in Working Dogs before and after Three Different Field Trials

“…The elevation in rectal and muscle temperature resulting from prolonged exercise by dogs is associated with reduced levels of high energy phosphates (ATP and CrP) and increased levels of muscle lactate, pyruvate, and AMP, which may contribute to fatigue [13]. In greyhounds a limited, but positive, association between ambient temperature and post-exercise body temperature has been observed [14]. Those authors reported that when ambient temperature reached 38 • C, 39% of the included dogs showed a RT > 41.5 • C. The mean increase in rectal temperature was greater in dark than light colored greyhounds, and, in the post-race observation, in males than in females.…”