Sweating rates from heat-stressed dairy cows and beef heifers were measured using a "Portable Calorimeter" and a "Bovine Evaporation Meter" designed and fabricated for the studies reported herein. Measurements were taken when cows were in their natural habitat. The focus of the study was to compare sweating rates measured from different breeds of dairy cows and beef heifers, and determine the level of influence of environmental factors (air temperature, relative humidity, solar load, and air velocity) and hair-coat color on sweating rate. The cows were exposed to solar radiation greater than 500 W/m 2 (average 833 ±132 W/m 2), average THI was 82.7 ± 1.64 for all studies except for the Nebraska data where the THI was 77.4 ± 4. Air velocity in the sample area was between 0.8 and 1.2 m/s, and body (rectal) temperature was greater than 38.8°C (threshold for heat stress). Sweating rates ranged between 189 ± 84.6 and 522 ± 127.7 g/m 2-h. Body temperature ranged between 39.3 ± 0.53°C and 41.7 ± 0.19°C. Differences in sweating rates were statistically significant at P < 0.05 between breeds, between black and white hair coats, and changes in solar load, relative humidity, and air velocity. Wetting the skin surface and increasing air velocity profoundly increased evaporation rate by converting sensible heat to latent heat.

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Digital infrared thermal imaging (DITI) using a thermal camera has potential to be a useful tool for the production animal industry. Thermography has been used in both humans and a wide range of animal species to measure body temperature as a method to detect injury or inflammation. The objective of these experiments was to compare the temperature of the eye (EYE) or muzzle (MUZ) measured using DITI to vaginal (VT) and rectal temperature (RT) as measures of core body temperature in hair sheep and beef cattle. In Exp.1 EYE, VT and RT were measured in lactating, multiparous hair sheep ewes (St. Croix White, n = 10, and Dorper × St. Croix White, n = 10) in a non-febrile state 5 times over a 48-h period. Data loggers were used to measure VT and a digital veterinary thermometer was used to measure RT. There was a high correlation (P < 0.001) between VT and RT (r = 0.95), EYE and RT (r = 0.76) and EYE and VT (r = 0.77). In Exp. 2 EYE, MUZ, VT and RT were measured in multiparous, lactating ewes (St. Croix White, n = 2, and Barbados Blackbelly, n = 12) at -12, -1, 0, 1, 2, 3, 4, 6, 12, 24, 36, and 48 h after being administered lipopolysaccharide (LPS; n = 7; 0.2 µg/kg BW, i.v.) or saline (n = 7; 0.5 mL, i.v.). Data loggers were used to measure VT and a digital veterinary thermometer was used to measure RT. When data were combined across treatments (LPS and saline) there was a high correlation (P < 0.001) between VT and RT (r = 0.96), EYE and RT (r = 0.82), MUZ and RT (r = 0.72), and EYE and VT (r = 0.93). In Exp. 3 EYE, MUZ, VT and RT were measured in multiparous, non-lactating, pregnant Senepol cattle (n = 44) between 0900 and 1200 h on a single day. A digital veterinary thermometer was used to measure both VT and RT. There was a high correlation (P < 0.001) between VT and RT (r = 0.78), a moderate correlation (P < 0.001) between VT and EYE (r = 0.52), RT and EYE (r = 0.58) and EYE and MUZ (r = 0.48). There was no correlation (P > 0.10) between RT or VT and MUZ. The findings of these three studies indicate that temperature of the eye, measured using DITI, can be used as an indicator of core body temperature in hair sheep and beef cattle as an alternative to using vaginal or rectal temperature.

This study was designed to determine the influence of temperament on endotoxin-induced changes in body temperature, sickness behavior, and stress hormone concentrations in cattle. Brahman bulls were selected based on temperament score measured 28 d prior to weaning. In dwelling recording devices were used to monitor rectal temperature, and jugular catheters were used to collect blood samples to determine cortisol and epinephrine concentrations before and after LPS administration (0.5 μg/kg body weight). Temperamental bulls had the lowest peak rectal temperature and sickness behavior scores relative to the Calm and Intermediate bulls. Prior to the administration of LPS, Temperamental bulls had greater cortisol and epinephrine concentrations than Calm or Intermediate bulls. Cortisol concentrations increased following LPS administration but were not affected by temperament. Epinephrine concentrations peaked 1 h after LPS administration in Calm bulls. Temperamental bulls did not exhibit an epinephrine response to LPS challenge. These data demonstrate that the temperament of calves can modulate the physiological, behavioral, and endocrine responses of pre-pubertal Brahman bulls to endotoxin challenge. Specifically, temperament differentially affected the rectal temperature, sickness behavior and epinephrine, but not cortisol, responses to LPS challenge.

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