Responses of simultaneously recorded intraperitoneal and subcutaneous temperatures of Black Bedouin goats to transient thyrosuppression during cold stress

Unlike poikilotherms, homeotherms resist wide amplitudes of core body temperature (T_core) fluctuation when exposed to reasonably variant ambient temperature (T_a) extremes. The degree of cold/heat thermotolerance varies tremendously amongst mammalian species. Thermotolerance can be partially inferred by the extent of resistance in body temperature displacement from normothermia when subjected to thermal stress. Regulation of thyroid calorigenic hormones is primarily contingent upon thermal homeostasis. Thyrosuppression generally exacerbates cold stress and hence may be a useful tool to examine the extent of cold-tolerance. An experiment was conducted to examine the extent of cold-tolerance on artificially goitrous Black Bedouin goats. Ten goat kids (initial Avg. BW = 30.6 ± 0.4 kg) were fitted with two miniature temperature data loggers, intraperitoneally and subcutaneously to identify core (T_core) and subcutaneous (T_sq) temperature responses, respectively, to chronically (47 days) cold (< 10 °C) environment along with or without oral administration of the thyreostat propylthiouracil (PTU 20 mg/kg BW/day). Five animals served as controls (CON) whereas the remaining five were treated with PTU for 31 out of the overall 47-day observation period. Despite its 74.5%-evoked transient depression of circulating free thyroxine (FT4), PTU-treatment failed (P > 0.10) to cause significant displacements in T_core or T_sq as compared to CON values throughout the 52-day trial period. As a function of T_a, T_core − T_sq thermal gradient revealed a significantly (P < 0.01) linear regression (r² = 0.41), to indirectly infer a graded blood redistribution from peripheral to splanchnic vascular beds with the fall in T_a. In the light of the current findings, it can be deduced that– in addition to the fact that it is superior in terms of heat-tolerance– the Black Bedouin goat is also profoundly cold-tolerant. Furthermore, our recently developed technique in concurrently recording T_core and T_sq proves efficient and feasible to simultaneously record temperatures of different body sites in free-roaming animals, thereby overcoming potentially erroneous artifacts caused by frequent experimenter intrusion.     

Heat stress: A major contributor to poor animal welfare associated with long-haul live export voyages

Recent investigations by the Australian Department of Agriculture, Fisheries and Forestry into high mortalities on live export voyages from Australia to the Middle East during the Northern hemisphere summer suggest that animal welfare may be compromised by heat stress. The live export industry has generated a computer model that aims to assess the risk of heat stress and to contain mortality levels on live export ships below certain arbitrary limits. Although the model must be complied with under Australian law, it is not currently available for independent scientific scrutiny, and there is concern that model and the mandated space allowances are inadequate. This review appraises the relevant literature on heat stress in sheep and cattle, including laboratory studies aimed at mimicking the ambient temperatures and humidity levels likely to be encountered on live export voyages. Animal welfare is likely to be very poor as a result of heat stress in some shipments.     

The relationships between scrotal surface temperature,age and sperm quality in stallions

In horses, spermatogenesis normally occurs at an average intratesticular temperature of 35 °C; therefore, mechanisms for testicular thermoregulation are essential. Measuring the scrotal surface temperature by thermography is one of the methodologies used to evaluate the effectiveness of testicular thermoregulation. The objective of this study was to determine the relationship between the control of scrotal surface temperature and sperm quality in horses of different ages. In total, 24 Quarter Horse stallions were divided into three groups: YS (young stallions), AS (adult stallions) and OS (old stallions). Initially, we calculated the testicular volume (TV) and evaluated various aspects of the semen (sperm kinetics, plasma membrane integrity and sperm morphology) for all the animals. We also evaluated rectal temperature (RT), body surface temperature (BST,) and average scrotal surface temperature in the testicular region (SST) before (M0) and after sun exposure (M1). Differences were observed (p<0.05) between the RT and BST before and after sun exposure in all three groups. However, there were no differences (p>0.05) in the SST values at these two time points, thus demonstrating the efficiency of the mechanisms for testicular thermoregulation. The SST was similar (p>0.05) among all three groups. Based on these results, we conclude that fertile stallions of different age groups are able to maintain SST and measuring the heat radiating from the scrotum using a digital infrared thermographer. We can also conclude that measuring the heat radiating from the scrotum using a digital infrared thermographer is a practical and efficient tool for monitoring SST in horses.     

阿维菌素与氟虫腈对小菜蛾3龄幼虫体温调节的影响

研究了阿维菌素与氟虫腈对小菜蛾3龄幼虫体温调节的影响。22±1℃温度下试虫经农药浸叶法处理24 h,再转入32±1℃条件。自转入新环境后1.0 min开始至试验结束,阿维菌素处理试虫体温都显著低于对照试虫(P<0.05),说明阿维菌素在所设浓度下影响试虫的体温调节能力;但氟虫腈处理过的试虫与对照体温无明显差异(P>0.05),表明在该浓度下氟虫腈对试虫体温调节影响较小。     

Monitoring the development of thermoregulation in poultry embryos and its influence by incubation temperature

The general purpose of this review is to show the stage of the development of peripheral and central nervous thermoregulatory mechanisms in poultry embryos at the end of incubation, and the impact of long-term changes in incubation temperature. Methods are described which (a) allow continuous measurement of peripheral thermoregulatory mechanisms simultaneously with the body temperature of the embryo, and (b) can be used for identification of changes in the sensitivity of the central controller of body temperature during the development as well as after prenatal temperature experiences. Further, a method for characterisation of ‘critical periods’ in the development of the respective body function is introduced.The results of our investigations were discussed in relation to the following general rules:(a) The development of peripheral and central nervous thermoregulatory mechanisms begins in the course of the prenatal ontogeny. At the end of incubation poultry embryos have all the prerequisites to react to changes in incubation temperature. Regarding the peripheral thermoregulatory mechanisms the most sensitive parameter for characterization of the developmental level of embryonic thermoregulation is the deep body temperature.(b) Functional systems of the organism develop from open loop system without feedback control into closed system controlled by feedback mechanism. Acute changes in the environmental conditions (e.g. incubation temperature) induce as a rule, initially uncoordinated and immediately non-adaptive reactions. Later the uncoordinated (immediately non-adaptive) reactions change into coordinated (adaptive) reactions, probably with closing of the regulatory system (‘critical period’). Environmental manipulation of immature physiological mechanisms could be used for characterization of ‘critical periods’ of the respective system. Monitoring of changes in the reactions of thermoregulatory mechanisms on the applied changes in incubation temperature during different perinatal time windows could help to limit ‘critical periods’ in the development of the thermoregulatory system.(c) During this ‘critical periods’, the actual environment modulates the development of the respective physiological control systems for the entire life period. Perinatal epigenetic temperature adaptation could be a tool to adapt poultry embryos or hatchlings to later climatic conditions. For detection of immediate and long-term effects of perinatal epigenetic temperature adaptation (‘imprinting’ of the thermoregulatory system) recordings of changes in neuronal hypothalamic thermosensitivity as well as in neuronal response on temperature stress are useful and have to be verified by identification of the respective effector genes and epigenetic changes in its expression.     

Swimming depth and thermal history of individual Atlantic salmon (Salmo salar L.) in production cages under different ambient temperature conditions

Salmon production cages at sites with a pronounced thermal stratification give individual fish an opportunity to choose their thermal environment. The behavioural responses of individual salmon to such stratification, however, are poorly documented. Information about spatial distributions and temperature experience of individual Atlantic salmon (initial weight 1.5 kg) was gathered over a period of 4 months (mid-August to early-December) using data storage tags. Fish were stocked at normal or high densities in triplicate 2000 m³ production cages at 5.6–14.5 (ND) or 15.7–32.1 (HD) kg m^− 3, and valid data were collected for 12 ND and 11 HD salmon. There were large inter- and intra-individual variations in swimming depth, with indications that the salmon performed behavioural thermoregulation in an attempt to maintain body temperature within the range of 8–20 °C. Stocking density influenced the average swimming depth and body temperature, indicating competition for preferred thermal space in periods of unfavourably high temperature (towards 20 °C) in large parts of the cage volume. Analysis of temporal behavioural patterns demonstrated a higher variability during day than night and that 60 to 70% of the individuals displayed cyclic diel patterns in either swimming depth or body temperature in at least one out of three sub-periods. The results are discussed in relation to bio-energetic and thermal stress theory and possible consequences for growth variation in salmon cages. Generally, this study suggests that individual swimming depth and body temperature is in part a response to available temperature interacting with stocking density and time of day, while some individual variation cannot be ascribed to the measured variables.     

Use of Water for Swimming and its Relationship to Temperature and Other Factors in Farm Mink (Mustela vison)

An investigation into swimming behaviour and its relationship to outdoor temperature was conducted in 40 ranch mink. Two different cage sizes were used and all animals had access to a basin filled with water 15 cm deep. During the years 1994-1998, water loss from the basin and temperatures at a nearby weather station were recorded once a week. In the last year 11 mink were video-recorded for 24 h. Using the monthly average daily water loss as an indicator, swimming activity showed a clear annual variation over 4 years and was positively correlated with average monthly temperature. With regard to swimming activity, a large individual variation existed: average water loss varied from 10 ml to nearly 4 litres per day, with those in large cage units having the greatest water loss. The video-recordings confirmed this variation: the number of swims ranged from zero to 177 during 24 h and there was an indication of more swimming bouts in the mink in the large cage units. The duration of swims varied from 2 to 55 s per bout. The relationship between swimming and general activity is discussed, along with the importance of water for swimming as a means of thermoregulation.     

Skin histology and its role in heat dissipation in three pinniped species

Background

Pinnipeds have a thick blubber layer and may have difficulty maintaining their body temperature during hot weather when on land. The skin is the main thermoregulatory conduit which emits excessive body heat.

Methods

Thorough evaluation of the skin histology in three pinniped species; the California sea lion-Zalophus californianus, the Pacific harbor seal-Phoca vitulina richardsi, and the Northern elephant seal-Mirounga angustirostris, was conducted to identify the presence, location and distribution of skin structures which contribute to thermoregulation. These structures included hair, adipose tissue, sweat glands, vasculature, and arteriovenous anastomoses (AVA). Thermal imaging was performed on live animals of the same species to correlate histological findings with thermal emission of the skin.

Results

The presence and distribution of skin structures directly relates to emissivity of the skin in all three species. Emissivity of skin in phocids (Pacific harbor and Northern elephant seals) follows a different pattern than skin in otariids (California sea lions). The flipper skin in phocids tends to be the most emissive region during hot weather and least emissive during cold weather. On the contrary in otariids, skin of the entire body has a tendency to be emissive during both hot and cold weather.

Conclusion

Heat dissipation of the skin directly relates to the presence and distribution of skin structures in all three species. Different skin thermal dissipation patterns were observed in phocid versus otariid seals. Observed thermal patterns can be used for proper understanding of optimum thermal needs of seals housed in research facilities, rescue centers and zoo exhibits.     

Infrared skin temperature measurements for monitoring health in pigs: a review

Infrared temperature measurement equipment (IRTME) is gaining popularity as a diagnostic tool for evaluating human and animal health. It has the prospect of reducing subject stress and disease spread by being implemented as an automatic surveillance system and by a quick assessment of skin temperatures without need for restraint or contact. This review evaluates studies and applications where IRTME has been used on pigs. These include investigations of relationships between skin, ambient and body temperatures and applications for detecting fever, inflammation, lesions, ovulation, and stress as well as for meat quality assessment. The best skin locations for high correlation between skin temperature and rectal temperature are most likely thermal windows such as ear base, eye region and udder. However, this may change with age, stressors, and biological state changes, for example, farrowing. The studies performed on pigs using IRTME have presented somewhat discrepant results, which could be caused by inadequate equipment, varying knowledge about reliable equipment operation, and site-specific factors not included in the assessment. Future focus areas in the field of IRTME are suggested for further development of new application areas and increased diagnostic value in the porcine and animal setting in general.