Heat loss efficiency and HSPs gene expression of Nellore cows in tropical climate conditions.

Adaptation is a relevant characteristic to be understood in livestock animals in order to maintain and raise productivity. In Brazil, the Nellore beef cattle are widely disseminated and well-adapted breed that present good thermoregulatory characteristics for tropical environment conditions. Conversely, the physiological and cellular mechanisms required for thermoregulation and thermotolerance in this breed are still limited. The aim of this study was to comprehend the heat loss efficiency at the whole animal level and heat shock response at the cellular level of Nellore cows in tropical climate conditions. Healthy purebred Nellore cows were classified according to their capacity to lose body heat as Efficient or Inefficient based on vaginal temperature which was continuously monitored by data-loggers. Rectal, tail, and ocular temperatures, sweating rate, and respiratory frequency were collected to assess other thermoregulatory responses. Peripheral mononuclear cells were used for gene expression of heat shock proteins 60, 70, and 90 induced by in vitro heat treatments at 38, 40, and 42 °C. In our findings, the Efficient cows presented higher sweating rates compared to Inefficient cows that presented higher rectal temperature with greater amplitude of vaginal temperature profile. Transcription of the HSP genes was stable at 38 and 40 °C and decreased for all HSP genes at 42 °C. In conclusion, the Nellore efficiency to lose heat was mainly associated with their sweating capacity and cellular thermotolerance confirmed by the maintenance of heat shock proteins transcripts under heat stress. Taken together, this knowledge contributes as a future key for genetic selection of adapted animals.

Termografia infravermelha da superfície ocular como indicador de estresse em suínos na fase de creche / Infrared thermography of the ocular surface as stress indicator for piglets postweaning

Desmama é uma fase crítica na vida do suíno devido a separação materna e a introdução de uma dieta seca. A termografia infravermelha medida na região ocular se mostra como um indicador confiável para a condição de estresse pontual de suínos. O objetivo deste estudo foi determinar a relação entre medidas de termografia infravermelha da superfície ocular e de cortisol em situações de estresse em leitões na pós desmama. Foram avaliados 66 leitões, uma vez por semana, durante sete semanas, em dois períodos do dia (7h e 15h) com medidas de temperatura superficial ocular, temperatura superficial do dorso e amostras de saliva para determinação de cortisol salivar. A análise estatística contemplou os efeitos fixos de semana e período do dia e sua interação e correlações de Pearson para relação entre termografia ocular, temperatura superficial e cortisol a 5% de significância. Cortisol salivar não diferiu entre os períodos, mas foi superior nas três primeiras semanas após o desmame (P<0,05). Nas duas primeiras semanas após a desmama o cortisol apresentou correlação alta e positiva (P<0,05) com a temperatura ocular máxima (0,89) e a temperatura superficial do dorso (0,80). As duas temperaturas superficiais apresentaram uma associação moderada positiva (r=0,41; P<0,0001) durante todo o período experimental. Este estudo destaca que a temperatura de superfície ocular obtida por meio da termografia infravermelha pode ser um indicador de temperatura de superfície corporal e estado de bem-estar de leitões em fase de creche, além de ser um método não invasivo e de rápida mensuração. Entretanto, mais pesquisas são necessárias para aprofundar a relação entre temperatura ocular e cortisol durante estresse crônico.(AU)

Weaning is a critical phase in pigs' life due to maternal separation and the introduction of a new diet. Infrared thermography measurement taken in the ocular region appears to be a reliable indicator of the stress condition of the pig. The aim of this study was to evaluate the relationship between ocular surface temperature by infrared thermography and cortisol in piglets post weaning. Sixty-six piglets were evaluated once a week, during 7 weeks, in two periods of the day (7am and 15pm) and ocular surface temperature and dorsal surface temperature were collected using a thermographic camera and a laser surface thermometer, respectively. Saliva was also collected to determine salivary cortisol. Statistical analysis included fixed effects of week and period of the day and their interaction, and relationship between thermography, dorsal surface temperature and cortisol were done by Pearson's correlations with 5% significance level. Salivary cortisol did not differ between periods, but it was higher in the first three weeks after weaning (P<0.05). During the first two weeks after weaning cortisol presented high and positive correlation (P<0.05) between ocular surface temperature (0.89) and dorsal surface temperature (0.80). The two superficial temperatures had a moderate and positive association (r=0.41; P<0.0001) during all experiment. This study highlights that the ocular surface temperature obtained through infrared thermography can be a superficial body temperature indicators, besides being a non-invasive and fast method of measurement. However, more research is needed to deepen the relationship between ocular surface temperature and cortisol during chronic stress.(AU)