Evaporative heat loss from group-housed growing pigs at high ambient temperatures

The effects of relative humidity and ambient temperature on evaporative heat loss were studied in 12 trials each with a group of 10 gilts with an initial BW of 61.7 kg (58.0–65.5 kg). The ambient temperature inside a respiration chamber was increased by 2 °C d⁻¹ starting at 16 °C and ending at 32 °C. Relative humidity was set at 50%, 65% or 80% and remained constant within each trial. The animals had free access to feed and water. Skin temperature (SkinT), total heat production (HP), evaporative heat loss (EvapH), respiration rate (RR), and wallowing of the animals were recorded. SkinT was lowest at 80% relative humidity (P<0.05). For each degree Celsius rise in SkinT, wallowing increased by 0.19% (P<0.05). For each degree Celsius rise in ambient temperature, total HP decreased by 115 kJ pig⁻¹ d⁻¹ and EvapH increased by 290 kJ pig⁻¹ d⁻¹ (P<0.05). It was concluded that under constant high ambient temperature and relative humidity, the pigs clearly employ respiratory evaporation to lose heat. Wallowing showed the importance of skin EvapH with higher temperatures, especially at high relative humidity. This study shows the importance of evaporative cooling from the skin. The implication is that pigs at high ambient temperatures, especially in combination with a high relative humidity, should be able to wet themselves. For animal welfare and environmental reasons, it is important that they are able to wet their skin.     

Extended stability of restriction enzymes at ambient temperatures

The stability of restriction enzymes as supplied by manufacturers without any modification has been examined. No reduction in activity was observed for three enzymes (HindIII, EcoRI and Tsp509I) held at ambient temperature or 4 degrees C for the period of study (12 months), while activity was observed for up to 12 weeks after storage at 37 degrees C, which was considerably better than following desiccation with trehalose, a recognized preservation technique. A larger trial of 23 different restriction enzymes held at room temperature for one week showed that all enzymes retained significant activity. As a practical demonstration of the usefulness of this finding, enzymes were posted to Africa by conventional mail (cost $1 US) and shown to retain activity upon arrival after three weeks in transit (compared to a cost of $1000 US by cold-chain transportation). Supplying enzymes to third-world markets should now be possible by removing the necessity for cold-chain transport. After arrival, enzymes can simply be stored in a standard domestic refrigerator.     

Effect of intraventricular injection of muscimol on appetite in rats kept at high and temperate ambient temperatures

The central mechanism controlling food intake in response to the change in environmental temperature has been little examined. The GABA agonist, muscimol, was injected into the lateral ventricle of rats which were acclimated to temperate (26 degrees C) and hot (33 degrees C) environments. Muscimol obviously stimulated the feeding behavior of rats in both environments. However, when muscimol was administered at doses of 100 and 250 ng, the food intake at 26 degrees C was greater than that at 33 degrees C. In addition, the stimulating effect of muscimol (250 ng) on food intake at 26 degrees C lasted longer than that at 33 degrees C. These findings suggested that there might be a difference in muscimol metabolism at the two temperatures.     

A method for preserving saliva samples at ambient temperatures

To facilitate biochemical and biopharmaceutical studies when cold storage is unavailable, we assessed the stability of saliva samples containing preservatives stored at room temperature over a 1-year period. Two preservative mixtures were evaluated: sodium benzoate and citric acid (P1), and ethyl and propyl paraben (P2). Saliva samples were spiked with acetaminophen (APAP) or antipyrine (AP) and stored in preservative-coated vials and examined for concentrations of APAP, AP, melatonin, and cortisol at regular intervals as a function of preservative type and storage duration. Samples were stored at room temperature or at -20 degrees C (positive control) and analyzed periodically for APAP and AP by high-performance liquid chromatography and for melatonin and cortisol by radioimmunoassay. The effectiveness of the preservatives was determined by calculating the value of samples stored at room temperature in terms of percent of control (-20 degrees C) values. P1 effectively maintained the stability of APAP (100%) and AP (100%) for 360 days at room temperature; concentrations in samples at room temperature on day 360 were comparable to those on day 01. P1 also effectively maintained melatonin (100%) and cortisol (95%) concentrations for 180 days at room temperature. P2 preserved AP and cortisol in saliva for 60 days, but APAP for only 14 days.     

Thermoregulatory consequences of long-term microwave exposure at controlled ambient temperatures

This study was designed to identify and measure changes in thermoregulatory responses, both behavioral and physiological, that may occur when squirrel monkeys are exposed to 2450-MHz continuous wave microwaves 40 hr/week for 15 weeks. Power densities of 1 or 5 mW/cm2 (specific absorption rate = 0.16 W/kg per mW/cm2) were presented at controlled environmental temperatures of 25, 30, or 35 degrees C. Standardized tests, conducted periodically, before, during, and after treatment, assessed changes in thermoregulatory responses. Dependent variables that were measured included body mass, certain blood properties, metabolic heat production, sweating, skin temperatures, deep body temperature, and behavioral responses by which the monkeys selected a preferred environmental temperature. Results showed no reliable alteration of metabolic rate, internal body temperature, blood indices, or thermoregulatory behavior by microwave exposure, although the ambient temperature prevailing during chronic exposure could exert an effect. An increase in sweating rate occurred in the 35 degrees C environment, but sweating was not reliably enhanced by microwave exposure. Skin temperature, reflecting vasomotor state, was reliably influenced by both ambient temperature and microwaves. The most robust consequence of microwave exposure was a reduction in body mass, which appeared to be a function of microwave power density.     

Short- and long-term responses to fescue toxicosis at different ambient temperatures

Intake of endophyte-infected tall fescue by cattle results in fescue toxicosis, which is characterized by increased hyperthermia during heat stress and concomitant reductions in feed intake and growth. Rats were monitored at 21 or 31 °C for short- or long-term periods to determine temporal changes associated with the intake of endophyte-infected (E+) or uninfected (E−) fescue seed diets. Core temperature only changed in rats fed E+ diet at 31 °C. Intake of E+ diet reduced feed intake, daily gain, and serum prolactin. There were temporal and thermal differences in the response to endophytic toxins, with short-term changes diminishing over time at 21 °C, but increasing for certain parameters at 31 °C.     

Behavioural responses of young cape gannets Sula capensis to high ambient temperatures

A young Cape Gannet Sula capensis responded to high ambient temperatures in the laboratory by standing, gular fluttering with raised head and open bill, wing drooping, defaecating at a fast rate close to or onto the feet, “paddling”; in the excreta, and increased breathing rate. Standing initially caused a decline in foot temperature which rose with rising ambient temperature. Gular flutter and wing drooping assisted the bird in tolerating heat stress. Reduction in heat‐load occurred when standing on a wet surface, presumably due to evaporative heat loss (of excreta on the feet = urohidrosis) and an enhanced conduction of heat to substrate. Field observations confirmed that young Cape Gannets defaecate onto their feet at high ambient temperatures. This species appears preadapted for this behaviour since it builds a solely guano nest, defaecating onto the rim which is compacted by “paddling”;.