Body temperature and thermoregulatory behaviour of the lizard Ameiva ameiva in Central Amazonian forests

Body temperatures and thermoregulatory behaviour of the teiid lizard Ameiva ameiva inhabiting the edge and the understory were studied in Central Amazonian forests Despite of differences in the thermal profile of the habitates. the mean body temperature was the some for active lizards observed at the edge or inside the forest. where only slight peculiarities in thermoregulatory behaviour were observed. A. ameiva is capable of maintaining body temperature significantly above microhabitat temperature.

Um Modelo para a Determinação do Equilíbrio Térmico de Bovinos em Ambientes Tropicais

An equation based on heat transfer theory was presented to estimate the rate of heat loss from cattle exposed to a tropical environment, specified by the air temperature, humidity, solar radiation, and wind speed. The animals' variables (sweating rate, rectal temperature, respiratory rate, surface temperature, haircoat color, and body weight) were considered together with environmental variables (air temperature and humidity, solar radiation, wind speed, and globe temperature). The equation allows the prediction of (a) the metabolic heat production level necessary to balance heat losses under specified environmental conditions; (b) the combination of environmental factors that provide a determined heat flux between a given animal and its environment.

The comparative efficacy of yohimbine and atipamezole to treat amitraz intoxication in dogs

This study compared the efficacy of yohimbine with atipamezole, a new α2-adrenergic antagonist, to treat canine amitraz intoxication. Thirty dogs were divided equally into 3 groups (A, AY, and AA). Group A received 2.5% amitraz iv at 1 mg/kg; Group AY received the same dose of amitraz followed 30 min later by 0.1 mg/kg (2 mg/mL) yohimbine iv; and Group AA received the same dose of amitraz followed 30 min later by 0.2 mg/kg (5 mg/mL) atipamezole iv. Temperature, heart rate, respiratory frequency, mean arterial pressure, degree of sedation, mean time of tranquilization and diameter of pupils were monitored for 360 min. Sedation, logs of reflexes, hypothermia bradycardia, hypotension, bradypnea and mydriasis were observed in Group A, with 3rd eyelid prolapse, increased diuresis and vomiting in some animals. Yohimbine reversed all alterations induced by amitraz, but induced significant cardiorespiratory effects such as tachycardia and tachypnea. Atipamezole was a useful antagonist for amitraz, with less cardiorespiratory effects, suggesting its potential role as an alternative treatment of amitraz intoxication in dogs.

Metabolic, ventilatory, and hygric physiology of the gracile mouse opossum (Gracilinanus agilis)

We present the first complete study of basic laboratory-measured physiological variables (metabolism, thermoregulation, evaporative water loss, and ventilation) for a South American marsupial, the gracile mouse opossum (Gracilinanus agilis). Body temperature (Tb) was thermolabile below thermoneutrality (Tb = 33.5°C), but a substantial gradient between Tb and ambient temperature (Ta) was sustained even at Ta = 12°C (Tb = 30.6°C). Basal metabolic rate of 1.00 mL O2 g-1 h-1 at Ta = 30°C conformed to the general allometric relationship for marsupials, as did wet thermal conductance (5.7 mL O2 g-1 h-1 °C-1). Respiratory rate, tidal volume, and minute volume at thermoneutrality matched metabolic demand such that O2 extraction was 12.4%, and ventilation increased in proportion to metabolic rate at low T a. Ventilatory accommodation of increased metabolic rate at low Ta was by an increase in respiratory rate rather than by tidal volume or O2 extraction. Evaporative water loss at the lower limit of thermoneutrality conformed to that of other marsupials. Relative water economy was negative at thermoneutrality but positive below Ta = 12°C. Interestingly, the Neotropical gracile mouse opossums have a more positive water economy at low Ta than an Australian arid-zone marsupial, perhaps reflecting seasonal variation in water availability for the mouse opossum. Torpor occurred at low Ta, with spontaneous arousal when . T b > 20°C. Torpor resulted in absolute energy and water savings but lower relative water economy. We found no evidence that gracile mouse opossums differ physiologically from other marsupials, despite their Neotropical distribution, sympatry with placental mammals, and long period of separation from Australian marsupials. © 2009 by The University of Chicago. All rights reserved.

Influence of environmental temperature, dietary energy level and sex on performance and carcass characteristics of pigs

Pigs are quite sensitive to high environmental temperatures and the thermoregulation mechanisms represent great expenses in energy for heating loss, reducing animal well-being and production performance, and altering carcass quality. The aim of this study was to assess the effects of sex and dietary energy level in growing-finishing pigs submitted to characteristic seasonal variation of temperature in subtropical humid climate, and to propose a mathematical model to predict growth performance and carcass characteristics. Twenty-eight crossbred growing-finishing pigs were randomly allotted to twelve treatments, in a 2x2x3 factorial trial (2 sex; 2 environmental conditions, and 3 energy levels). Heat stress condition (climatic chamber) showed temperatures of 31 oC at 7:00 and 22 oC at 17:00 (maximum of 33 °C) and thermal comfort condition (stall) showed temperatures of 18 °C at 7:00 and 24 °C (maximum of 27 °C). Pigs were fed ad libitum with diets containing 12.2 (low), 13.6 (medium) and 15.0 (high) MJ ME/ kg DM. Voluntary feed intake, daily weight gain, and final body weight were higher (P<0.01) at thermal comfort condition and were influenced by sex (P<0.01) in growing pigs. Feed to gain ratio decreased as the energy level increased (P<0.01), with values of 2.67, 2.59, and 2.32 (12.2, 13.6, and 15.0 MJ ME/kg DM, respectively). There was energy level and sex interaction only for daily weight gain. Regarding finishing pigs, environmental conditions also showed effects (P<0.01) on voluntary feed intake, daily weight gain, and final body weight. Performance of pigs was better at thermal comfort condition. Feed to gain ratio values were 3.55, 3.42, and 2.95 for low, medium, and high energy level, respectively. Interactions between energy level and sex were observed for voluntary feed intake, daily weight gain, and final body weight (P<0.05). Carcass yield and quality were affected by environmental condition and dietary energy level. Both hot and cold carcass weight increased as energy of ration increased. Cold carcass weight increased by 1.142 kg/MJ EM whereas backfat thickness was up to 252 mm/MJ EM. Longissimus thoracis muscle thickness was around 16 mm smaller in pigs under heat stress, but lean content was 2.68% higher in those animals. Regression equations were proposed to predict the performance values in the different situations studied.

Gaseous neurotransmitters and their role in anapyrexia

Mammals keep their body temperature (Tb) relatively constant even under a wide range of ambient temperature variation. However, in some particular situations it may be beneficial to increase or to decrease Tb. For instance, under hypoxic conditions, a regulated drop in Tb (anapyrexia) takes place which has been reported to be crucial for survival in a number of different species. This review highlights major advances in the research about nitric oxide (NO) and carbon monoxide (CO-where data are relatively less abundant), before focusing on the role played by these gaseous neuromediators in thermoregulation, under the conditions of euthermia and anapyrexia. Available data are consistent with the notion that both NO and CO, acting on the CNS, participate in thermoregulation, with NO decreasing Tb and CO increasing it. However further studies are required before definitive conclusions can be made as to their physiological mechanisms of action.

Serotonergic neurons in the nucleus raphé obscurus are not involved in the ventilatory and thermoregulatory responses to hypoxia in adult rats

The medullary raphé is an important component of the central respiratory network, playing a key role in CO2 central chemoreception. However, its participation in hypoxic ventilatory responses is less understood. In the present study, we assessed the role of nucleus raphé obscurus (ROb), and specifically 5-HT neurons confined in the ROb, on ventilatory and thermoregulatory responses to hypoxia. Chemical lesions of the ROb were performed using either ibotenic acid (non-specific lesion; control animals received PBS) or anti-SERT-SAP (5-HT specific lesion; control animals received IgG-SAP). Ventilation (VE; whole body plethysmograph) and body temperature (Tb; data loggers) were measured during normoxia (21% O2, N2 balance) and hypoxia exposure (7% O2, N2 balance, 1h) in conscious adult rats. Ibotenic acid or anti-SERT-SAP-induced lesions did not affect baseline values of VE and Tb. Similarly, both lesion procedures did not alter the ventilatory or thermoregulatory responses to hypoxia. Although evidence in the literature suggests a role of the rostral medullary raphé in hypoxic ventilatory responses, under the present experimental conditions our data indicate that caudal medullary raphé (ROb) and its 5-HT neurons neither participate in the tonic maintenance of breathing nor in the ventilatory and thermal responses to hypoxia. © 2013 Elsevier B.V.

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. © 2013 Elsevier B.V.

Ecologia termal da jararaca-ilhoa, Bothrops insularis (Serpentes, Viperidae): um estudo em condições naturais

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Fatores causais do grau de limpeza de vacas leiteiras e suas relações com a contagem de células somáticas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Determinantes da resposta termofílica pós-prandial em Crotalus durissus terrificus (Squamata: Viperidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morfologia e taxonomia de Atractus latifrons (Günther, 1868) (Serpentes: Dipsadidae) e seu relacionamento mimético com corais verdadeiras na Amazônia

A coloração animal é um importante atributo biológico com diferentes funções relacionadas às estratégias de vida adotadas pelos indivíduos no ambiente, como a termorregulação, a defesa e a comunicação inter e intraespecífica. O mimetismo é talvez, um dos mais importantes mecanismos biológicos de comunicação, frequentemente envolvendo similaridade de cor com conotação defensiva. Os sistemas miméticos refletem um complexo processo de evolução, que acentua semelhanças morfológicas ou comportamentais entre duas ou mais espécies, garantindo vantagens adaptativas em pelo menos uma delas. Apesar de comum entre os invertebrados, o mimetismo também pode ser observado em grupos de vertebrados como lagartos e serpentes, por exemplo. Dentre os exemplos mais comuns de mimetismo em serpentes são descritas as relações entre os corais verdadeiras e falsas. A falsa-coral, Atractus latifrons (Günther, 1868) é endêmica da Amazônia e ocorre nos territórios de Brasil, Colômbia, Guiana Francesa, Peru, Suriname e Venezuela. Em função da semelhança cromática de seus diferentes padrões, esta espécie foi relacionada à algumas espécies de corais verdadeiras do gênero Micrurus que também apresentam distribuição amazônica. Embora a variação cromática desta espécie tenha sido relatada por alguns autores, algumas questões sobre o polimorfismo intraespecífico e sua relação com a distribuição geográfica, assim como a relação mimética com as corais verdadeiras de Micrurus ainda não foram estudadas. Com o objetivo de contribuir com a elucidação destas questões, este estudo foi organizado em dois capítulos: no primeiro capítulo, intitulado “Variação morfológica e taxonomia de Atractus latifrons (Günther, 1868) (Serpentes: Dipsadidae)”, foram apresentadas as variações da morfologia externa e hemipeniana da espécie, incluindo sua redescrição e descrição do holótipo, além das descrições dos padrões cromáticos e análise de dimorfismo sexual; e no segundo capítulo, intitulado “Relações miméticas entre Atractus latifrons e corais verdadeiras na Amazônia”, foram identificados os possíveis modelos miméticos para A. latifrons, inferindo suas relações miméticas através da análise de co-ocorrência e apresentando mapas de distribuição dos padrões miméticos entre as espécies envolvidas.

Conforto térmico e eficiência da inseminação artificial em tempo fixo em búfalas leiteiras mantidas em sistemas silvipastoris na Amazônia Oriental

O trabalho foi desenvolvido na U.P.A. “Senador Álvaro Adolpho”, Embrapa Amazônia Oriental, Belém, Pará (1º25¢ S 48º26¢ O), local de tipo climático Afi (quente e úmido). O objetivo foi avaliar o uso de sistemas silvipastoris (SSP) como ferramenta de manejo para proporcionar maior conforto térmico a búfalas leiteiras, e incrementar sua eficiência reprodutiva após a utilização da inseminação artificial em tempo fixo. Foram utilizados dois SSP´s, durante dois períodos do ano, onde: Período 1 (Abril a Junho), com maior precipitação pluviométrica e Período 2 (Setembro a Novembro), com menor precipitação pluviométrica. Foram mensuradas a freqüência cardíaca (FC), freqüência respiratória (FR), temperatura retal (TR) e movimentos ruminais (MR), sempre às 9h00min. O índice de conforto animal foi calculado conforme a fórmula: ICA = TR/38,33 + FR/23. Os animais de cada sistema foram tratados com dois diferentes protocolos para sincronização do estro e ovulação, formando os Grupos SSP 1/Ovsynch, SSP 2/Ovsynch (estro sincronizado com Ovsynch), SSP 1/Prog e SSP 2/Prog (estro sincronizado com Ovsynch + 1g de progesterona intravaginal). Os ovários de todas as búfalas foram monitorados por ultra-sonografia no D0, D7 e D9 e as búfalas foram inseminadas no D10 (D0=dia do início da sincronização). As médias de FC foram de 57,35±8,24 bat/min no Período 1 e 62,48 ±7,79 bat/min no Período 2 (P<0,01). A FR média foi de 25,66 ±10,53 mov/min no Período 1 e de 33,38 ±18,23 mov/min no Período 2 (P<0,01). Os animais mantidos no SSP 1 apresentaram TR superior aos do SSP 2 (39,02 ±0,53ºC versus 38,65 ±0,41ºC, P<0,01). As médias do ICA variaram entre 1,89 e 3,55. No Período 1 obteve-se variação de 1,89 a 2,42 e média de 2,12 ±0,46. No Período 2, a média do ICA foi de 2,46 ±0,79, com variação de 1,91 a 3,55. Houve diferença significativa das médias de ICA entre os períodos (P<0,01). O diâmetro do folículo dominante no D9 foi superior para os animais que receberam progesterona (10,40 ±1,22 mm versus 12,21 ±3,42 mm; P=0,05). A taxa de prenhez total foi de 48,21%, sendo que no Período 1 houve 56,66% de fêmeas gestantes, contra 38,46% no Período 2 (SSP1/Ovsynch: 40,0%; SSP2/Ovsynch: 38,46%; SSP1/Prog: 46,66% e SSP2/Prog: 69,23%; P>0,05). Com base nos resultados, ressalta-se a importância do manejo do ambiente físico para a criação de bubalinos na Amazônia Oriental, o que pode evitar gastos energéticos para a termorregulação animal e possibilitar melhores índices reprodutivos.

Aspectos fisiológicos de Chrysomya megacephala (F.) (Diptera: Calliphoridae): metabolismo energético, termorregulação e neurofisiologia

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Termografia infravermelho na estimativa de conforto térmico de frangos de corte

Poultry facilities must provide an environment that ensures thermal comfort allowing the animal to express its genetic potential for production; and new tools are being applied to measure the thermal comfort, especially thermal cameras. The objective of this study was to evaluate the association of the surface temperature of the birds with those from the facilities, and estimate the sensible heat transfer. For this, the thermal conditions of rearing in two aviaries with different ventilation systems, during the period of March to April 2011 were recorded. The aviaries were divided into six quadrants for the registration of surface temperatures obtained using an infrared thermal camera. In each quadrant the ambient temperature, relative humidity and wind velocity during the obtention of images were also recorded. It was observed that the surface temperatures of birds are associated with the surface temperature of the rearing facilities (side curtains, roof and litter). In aviary with negative pressure higher wind speeds compared to the conventional one were recorded and; therefore, allowed a higher sensible heat transfer by birds, suggesting that this provided better conditions for thermal comfort.