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

Abstract

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.

Silvopastoral system is an alternative to improve animal welfare and productive performance in meat production systems

“…However, during the autumn, heifers of the silvopastoral system reached basal levels of cortisol (5–10 ng/mL) 36 , while cows maintained cortisol levels above baseline 37 in both systems. Although a reduction in gene expression of HSP90AA1 in cows allocated in shaded pastures was expected, levels did not differ nor were influenced by variation of climatic conditions, being similar to that found in zebu cattle 38 . It is possible that signaling of thermal stress at the cellular level occurs due to a cumulative exposure, as already reported in some studies 12 , 16 , 39 , and it should be considered that these effects may become evident only after longer periods of animal exposure to the stressor stimulus.…”

Análise de parâmetros fisiológicos e perfil de expressão de genes associados ao estresse térmico e eficiência alimentar em bovinos das raças Nelore e Caracu

“…In the present study, the expression levels of the HSP70 gene were similar between the groups formed and between the breeds studied. Similar HSP70 gene expression results have been reported in Nelore females subjected to heat stress, with no difference between heat-tolerant and non-tolerant animals (Hooper et al, 2019). The expression levels of the HSP70 gene did also not differ between Simmental and Angus animals (Rocha et al, 2019).…”

“…Differences in HSPD1 and HSP90AA1 relative expression were observed between Caracu and Nelore breeds, corroborating that zebu cattle are naturally adapted to different climatic conditions. Hooper et al (2018), in a study of Nelore cows, described the expression of HSPD1 fluctuating from 0.93 (42 °C) to 1.20 (40 °C), while we observed that the relative expression of HSPD1 ranged from 0.17 to 7.87 in Nelore and from −1.91 to 6.97 in Caracu steers during sun exposure (36.35 °C to 41.96 °C) in all months studied.…”

“…We demonstrated that breed and treatment did not influence the relative expression of HSPA1A. Hooper et al (2018) also did not find significant differences in the expression of hsp70 in Nelore cows that were efficient or inefficient at dissipating heat. , in a study on Tharparkar (zebu cattle) bull sperm, did not detect significant differences in HSPA1A expression between the summer and winter seasons.…”

“…The HSP90AA1 upregulation during heat stress resulted from fast induction of hsp90 protein translation to protect the cells from heat stress (Collier et al, 2008). Previous studies also reported that HSP90AA1 is upregulated owing to climatic conditions and physiological characteristics in taurine and zebuine cattle breeds Kumar et al, 2015;Hooper et al, 2018). The lower expression of HSP90AA1 detected in February can be associated with physiological parameters and climatic conditions.…”