The objective of this study was to evaluate the effect of pregnancy, breed, and hair coat on body temperature and sweating rate (SR) of hair sheep. St. Croix White (STX; = 9) and Dorper × STX (DRPX; = 9) ewes (3.6 yr of age) were evaluated over 4 d at 126 d of gestation (PREG) and over 4 d at 46 d postpartum (OPEN) in the shade and sun and in the morning (AM; 0900 to 1200 h) and afternoon (PM; 1300 to 1600 h) after a 20 min acclimation to each condition on each day. Data loggers recorded vaginal temperature (VT) at 10-min intervals for 96 h. Rectal temperature (RT) was measured using a digital veterinary thermometer, and respiration rate (RR) was measured as breaths per minute (bpm). Sweating rate was calculated from measured air properties passing over a shaved (300 cm) and unshaved area of the ewes' body using a portable calorimeter. Data were analyzed using GLM procedures of SAS (SAS Inst. Inc., Cary, NC) with breed, pregnancy status, sun exposure, and time of day as main effects. Mean temperature, relative humidity, temperature-humidity index, wind speed, and solar radiation on the days of data collection were 28.2°C, 82.8%, 80.3, 4.2 km/h, and 237.5 W/m, respectively. There was no difference ( > 0.10) in RT, RR, and SR between DRPX and STX ewes. The PREG ewes had lower RT ( < 0.007) and SR ( < 0.0001) and higher RR ( < 0.007) than OPEN ewes (38.5 ± 0.2 vs. 39.1 ± 0.2°C, 70.2 ± 3.1 vs. 88.3 ± 3.1 g⋅m⋅h, and 79.5 ± 2.2 vs. 72.1 ± 2.2 bpm, respectively). During the PM, RR, RT ( < 0.05), and SR ( < 0.006) were higher than in the AM. In the sun, RR ( < 0.001) and SR ( < 0.0001) were higher than in the shade, but there was no difference ( > 0.10) in RT. There was no difference in SR ( > 0.10) between the shaved and unshaved area of the ewe. The DRPX ewes had higher ( < 0.0001) VT than STX ewes. The PREG ewes had higher ( < 0.001) VT than OPEN ewes during the night time and lower VT than the OPEN ewes during the day time ( < 0.0001). The OPEN ewes had a greater ( < 0.009) daily range of VT than PREG ewes did (2.5 ± 0.4 vs. 1.1 ± 0.4°C, respectively), but there was no breed difference ( > 0.10). Hair coat did not have an influence on the SR of the ewes, and PREG ewes appeared to use increased respiration as opposed to sweating to help control RT. The narrower range of body temperature, measured as VT, of PREG compared to OPEN ewes may be a protective mechanism for the developing fetus.

No description available.

In the present study, the influence of various drug pretreatments will be investigated in the rabbit in an attempt to (a) define the pharmacological mechanism of action of pipradrol in its mediation of hyperthermia and (b) observe the effects of these pretreatments on the behavioral effect of pipradrol. Although pipradrol is no longer of clinical utility, it is hoped that the results of this study may provide more information for its use in future studies as a pharmacological tool.

As chickens hatch, there is a rapid change in their physiology and metabolism associated with attaining endothermy. It is thought that thyroid hormones (TH) play a major role in regulating developmental changes at hatching. In birds, TH regulates skeletal muscle growth, which has a direct impact on the chick's ability to thermoregulate via shivering thermogenesis. To better understand the role of TH in the timing of hatching, development of thermogenic capacity, and metabolic rate, we manipulated plasma TH levels in chicken embryos beginning at 85% development (day 17 of a 21 day incubation) with either thyroperoxidase inhibitor methimazole (MMI) or supplemental triiodothyronine (T3). After TH manipulation, we characterized O2 consumption and body temperature in the thermal neutral zone and during gradual cooling. Externally pipped embryos and 1 day post hatch (dph) chicks were cooled from 35 to 15°C. Manipulation of TH altered the timing of hatching, accelerating hatching under hyperthyroid conditions and decelerating hatching with hypothyroid conditions. Cohen's d revealed a large effect size on body temperature (Tb) of EP embryos of hypothyroid animals when compared to euthyroid animals in environmental temperatures of 32°C to 15°C, which was not seen in 1dph animals. Hyperthyroid EP animals were able to maintain metabolic rate over a wider range of ambient temperatures compared to control and hypothyroid animals, but these differences disappeared in 1dph animals. Here, we find that elevating TH levels prior to hatching accelerated hatching and the animal's thermogeneic ability to respond to cooling, but these differences disappear with age.

Goldfish (Carassius auratus) (40-80g) were injected with dopamine into the forebrain to study the possible involvement of this amine in central temperature regulation in these fish. Dopamine caused a decrease in selected temperature after injection into the rostral nucleus preopticus periventricularis (NPP). This effect was dependent on the dose of dopamine administered. Doses of 25, 50, 100 and 250 ng were used, injected in a volume of 0.2μ1. Injections in regions adjacent to the NPP elicited hypothermic effects only at the higher dosages. These effects were not consistent. Injections in caudal regions of the NPP elicited no effect. The effects of dopamine were blocked by haloperidol, a selective antagonist of dopamine. It is suggested that dopamine acts on central thermoregulatory neurons, present in the rostral NPP, in the mediation of thermoregulatory behavior. Further, it is suggested that this action is mediated via dopaminergic receptors.

The relative contribution of arteriovenous oxygen (A-V O2) difference to thermally-induced and activity-induced changes in metabolic rate (VO2) were delineated in the toad, B. marinus. In conjunction, the influence of rest and activity, temperature, and removal of the pericardia! sac on separation efficiency (Es) in the anuran ventricle was determined by direct measurement of arterial and venous percent oxygen saturation (% saturation), using a microsampling technique.

The primary goals of this research were to develop an improved design for measuring tympanic temperature in groups of beef cattle, determine the ideal operating parameters of the new device, and to verify its effectiveness in a research application. Development of the continuous tympanic temperature logger (CTTL) consisted of two steps: identifying a small temperature logger capable of adequate data storage and constructing a probe to hold the logger and fit in the ear canal of a bovine animal. The minimum sampling interval needed to measure tympanic temperature in beef cattle was calculated using Fourier analysis. In addition, the differences in core body temperature between three measurement locations (left ear, right ear, and vagina) were quantified. The CTTL was also used to record the thermoregulatory responses of feedlot heifers with access to shade provided by three different materials.

Purpose: Reducing body temperature before exercise is called precooling. Past research suggests that reducing body core temperature (Tc) slightly can result in improved running performance. This study evaluated the effects that warming up, while wearing a cooling vest prior to an interval workout, had on Tc, and interval time in long-distance runners. Methods: Nineteen healthy male collegiate cross-country runners were recruited for this study. Each subject warmed up and exercised under two different conditions: (a) an experimental condition in which subjects wore a Nike PreCool® ice vest during warm-up and (b) a control condition. Subjects performed a warm-up followed by running eight 1000 m intervals separated by 90 s of rest. Heart rate (HR) and Tc were measured prior to warm-up, just prior to start of the first interval, and after each interval. Results: Tc measured directly prior to the first interval was significantly lower in the vest condition than the non-vest condition (difference = 0.37°C; P < 0.05). This difference persisted through the end of the sixth interval. Tc rose at a faster rate in the non-vest condition, though this difference was not significant (P = 0.07). Differences in HR and interval times were found to be nonsignificant between conditions for all intervals. Conclusion: Wearing an ice vest prior to and during warm-up effectively lowers Tc during long-distance interval training.

Six adult male volunteers of similar body composition and physical fitness were tested to determine plasma immunoreactive β-endorphin (Piβ-EN) response under three conditions of exercise thermoregulatory stress. The experimental protocol consisted of 120 min of stationary upright cycling at 50% Vo₂max under conditions of neutral (24ºC, 50% RH)/euhydration (NE), hot (35°C, 50% RH)/euhydration (HE), and hot/dehydration (HD). Piβ-EN was measured by radioimmunoassay at -30 min, 0 min, and at 15 min intervals thereafter. Change in plasma volume (ΔPV) was measured to determine its effect on Piβ-EN concentration. Preexercise Piβ-EN levels averaged 23.7 ± 2.6 pg•ml⁻¹ in all conditions. The greatest Piβ-EN response occurred at 105 min in HD conditions when levels rose to 43.2 ± 6.9 pg•ml⁻¹. Exercise in HD and HE conditions resulted in significantly (p < 0.05) elevated Piβ-EN above levels observed in NE. ΔPV did not account for more than 10% of Piβ-EN changes at any interval. The Piβ-EN response pattern closely resembled rectal temperature changes in all conditions. These data suggest that conditions of increasing exercise thermoregulatory stress are associated with increasing peripheral β-endorphin concentration. / Master of Science

Tall fescue is a widely grown, cool season grass prevalent in the eastern United States that is known for its resistance to abiotic and biotic stresses. A main reason for tall fescue's resistance to these stresses is attributed to the presence of a fungal endophyte. Unfortunately, this endophyte also adversely affects cattle production. Cows consuming the ergot alkaloids produced by these endophytes can exhibit decreased feed intake, growth performance, organ vasoconstriction, and increased rectal temperature. This work is interested in examining how endophyte toxin exposure impacts pregnancy in cattle. Reduced blood flow to the fetus and inadequate maternal nutrition contributes to intra uterine growth restriction (IUGR), and this work proposed that fescue endophyte toxicity affects the gestating cow and fetus. Three studies were completed. In experiment 1, gestating cows grazed high or low endophyte fescue pastures during late gestation to determine if exposure to ergot alkaloids in utero results in IUGR and if calves from these pregnancies have altered growth performance. Creep feeding was evaluated as a mitigation strategy for impaired calf growth due to fescue toxicity, and feedlot performance was evaluated to determine if consuming fescue during gestation and creep feeding would affect feedlot performance. Calf BW was different (P < 0.01) by treatment x time. Birth weights of calves were similar , prior to creep feeding calves exposed to high endophyte fescue were lower, and post-supplementation creep fed calves had increased BW. Days on feed and dressing percentage were decreased in the supplemented group, and marbling score was decreased for both the supplemented and unsupplemented groups following the completion of the feedlot phase (P < 0.05). The second study was setup similar to study one, however cows were exposed to fescue pastures from d 170 of gestation until calving. Calf birth weights did not differ, but weights were increased in the supplemented group post creep feeding (P < 0.05). Average daily gains (ADG) of supplemented calves were greater during the supplementation period (P < 0.01). In the third study, indwelling vaginal temperature probes were used to evaluate differences in body temperature of cows fed fescue seed with high or low levels of ergot alkaloids during early gestation, and in varying environmental conditions. In the winter trial, body temperature was measured hourly from days 0-14 of gestation. In the summer trial, body temperature was measured hourly from days 0-32 of gestation. Body temperatures were different (P < 0.01) between treatments during both trials. / Master of Science