Evaluating the impact of breed, pregnancy, and hair coat on body temperature and sweating rate of hair sheep ewes in the tropics.

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.

Placement of temperature probe in bovine vagina for continuous measurement of core-body temperature.

There has been increasing interest to measure core-body temperature in cattle using internal probes. This study examined the placement of HOBO water temperature probe with an anchor, referred to as the "sensor pack" (Hillman et al. Appl Eng Agric ASAE 25(2):291-296, 2009) in the vagina of multiparous Holstein cows under grazing conditions. Two types of anchors were used: (a) long "fingers" (4.5-6 cm), and (b) short "fingers" (3.5 cm). The long-finger anchors stayed in one position while the short-finger anchors were not stable in one position (rotate) within the vagina canal and in some cases came out. Vaginal temperatures were recorded every minute and the data collected were then analyzed using exponential mixed model regression for non-linear data. The results showed that the core-body temperatures for the short-finger anchors were lower than the long-finger anchors. This implied that the placement of the temperature sensor within the vagina cavity may affect the data collected.

Vasomotion in chicken foot: dual innervation of arteriovenous anastomoses.

Blood exits the foot of the domestic chicken via two major venous routes: a counter-current network surrounding the major incoming artery and a large collateral vein. Between these two routes are numerous large collateral vein. Between these two routes are numerous anastomotic veins. Both venous routes drain capillaries and arteriovenous anastomoses (AVAs). Blood flow through the foot was measured on unanesthetized hens. Flow varies with ambient temperature: 0.2 ml/min at 5 degrees C, 2.2 ml/min at thermoneutrality, and 5.4 ml/min at 36 degrees C; the AVAs contribute 8, 26, and 63% to this flow, respectively. Flow through capillaries is reduced by alpha-adrenergic agonists and is increased by beta-adrenergic agonists. Blocking nerve conduction to the foot at thermoneutrality releases alpha-adrenergic tone and increase AVA flow. Faradic stimulation of foot nerves after adrenergic blockage increases AVA flow, but not capillary flow, suggesting active vasodilation of the AVAs. Such AVA vasodilation normally occurs during body heating, since AVA flow decreases after denervation. Dopaminergic or beta-adrenergic nerves are not involved in active vasodilatation, however, purinergic nerves may play a role. Thus AVAs have a functional dual innervation.

Effect of energy restriction on total heat production, basal metabolic rate, and specific dynamic action of food in rats.

Man and experimental animals are able to adapt to restricted levels of energy intake mainly by a reduction in basal metabolic rate (BMR) while the effects of energy restriction on the specific dynamic action (SDA) of food and the spontaneous activity are less well established. In this study, growing rats were fed ad libitum or restricted amounts of diet during 28-31 days. Then total heat production (THP) and BMR during 22 hours, as well as SDA of a test meal, were measured on individual rats by indirect calorimetry. After the calorimeter study rats were kept in metabolic cages for 6 days after which they were killed and analyzed for total body composition. The energy balance of the rats over the last 7 days of the study was calculated from changes in body composition and measurements of food intake during this period. During the calorimeter experiment an indirect estimation of the spontaneous activity of the rat was made. Results showed that THP, BMR and SDA of restricted rats were significantly lower than for ad libitum-fed rats. From body composition measurements, rats restricted in food intake before the calorimetry study were found to mobilize more protein and less fat compared to rats fed ad libitum until the calorimetry and body composition studies were carried out. No difference in spontaneous activity was observed between the two dietary treatments.

Effects of 6-hydroxydopamine and pimozide on temperature maintenance by the chicken.

Intraventricular implants of pimozide in adult white leghorn hens were used to block dopamine (DA) receptors, and 6-hydroxydopamine (6-OHDA) was injected intraventricularly to destroy the noradrenergic system locally. The hens were exposed to ambient temperatures of 5 and 35 degrees C, and their core temperature was measured. One hundred micrograms of 6-OHDA significantly reduced the norepinephrine (NE) but not the DA content of the hypothalamus and reduced the uptake of [3H]NE but not of [3H]DA by synaptosomes in vitro. Neither of the drug treatments nor their combination affected average core body temperature (Tb) at either 5 or 35 degrees C. Pimozide treatment caused a lower maximum Tb at 35 degrees C and a higher maximum Tb at 5 degrees C than the control treatment. No evidence was obtained that 6-OHDA treatment affected body temperature regulation. It is concluded that neither the DA nor the NE system is essential for normal temperature maintenance in the hen exposed to either 5 or 35 degrees C.

Effect of 5-hydroxytryptamine and acetylcholine on the energy budget of chickens.

Intraventricular injections of 5-hydroxytryptamine-HCl (258 nmol) or acetylcholine-HCl (550 nmol) in the chicken caused body temperature to rise at 35 degrees C ambient, a result of decreased evaporative heat loss due to bradypnea. At 10 and 20 degrees C ambient, neither drug affected body temperature. Although these drugs decreased physical activity or shivering or both at 10 and 20 degrees C, metabolic heat production was not depressed enough to alter body temperature significantly. Heart rate decreased simultaneously with decreased activity at 20 degrees C. This study is the first to inject 5-hydroxytryptamine as a salt of HCl, instead of creatinine sulfate, as is commonly used. It is suggested that some of the differences reported herein, compared to other studies, are due to the type of salt used. It is postulated that either 5-hydroxytryptamine or acetylcholine, rather than norepinephrine, may be an important neurotransmitter in the neural pathways for thermoregulation in chickens, even though their action on thermoregulation is minor compared with norepinephrine.

Impact of centrally applied biogenic amines upon the energy balance of fowl.

The impact of intraventricular injections of 100 microng of the biogenic amines, norepinephrine or dopamine, upon the energy balance of white leghorn hens Gallus domesticus was examined. Both drugs reduce metabolic heat production (about 35% at 9 and 20 degrees C, and about 15% at 35 degrees C) by inhibiting shivering or by reducing activity or both. Also the drugs inhibit the opposing thermal response, evaporative heat loss (about 3% at 9 and 20 degrees C, and about 20% at 35 degrees C) by reducing respiration rate. The relative balance of inhibiting these opposing responses by the drugs results in hypothermia at 9 and 20 degrees C, and hyperthermia or no change in body temperature at 35 degrees C. Both drugs usually caused an initial vasodilation of the feet and comb at all temperatures tested but did not persist long enough to have much of an impact on body temperature. It was concluded that differing ambient temperatures do not alter the action of the biogenic amines upon the modes of physical thermoregulation in chickens even though the direction of body temperature change is reversed at different ambient temperatures.