Differences in body temperature, cell viability, and HSP-70 concentrations between Pelibuey and Suffolk sheep under heat stress

Abstract

Pelibuey and Suffolk sheep were compared as to their capacity to regulate body temperature under environmental hyperthermia by measuring their differences in cellular response to heat stress (HS). In a first experiment, seven Pelibuey and seven Suffolk ewes were kept in a climatic chamber for 6 h daily during 10 days (temperatures within the 18 to 39.5 °C range). As chamber temperature rose, sheep rectal temperature increased in both groups, but to a lesser extent in Pelibuey (0.3 °C) than in Suffolk sheep (0.7 °C) (P < 0.05). In a second experiment, cellular viability was assessed using cultured blood mononuclear cells from 15 Pelibuey and 15 Suffolk sheep. They were incubated at 37 °C for 24 h (control) or 43 °C for 6 h followed by 18 h at 37 °C (HS). In a third experiment, another blood mononuclear cells culture from eight Pelibuey and eight Suffolk sheep was kept at 37 °C for 15 h; these were subsequently cultured for 6 h at 37 °C (controls) or 43 °C (HS). Next, HSP-70 concentration was determined. HS reduced the percentage of viable cells to a greater extent in Suffolk [37 °C (73.7 %) vs. 43 °C (61.9 %); P < 0.05] than in Pelibuey sheep [37 °C (74.9 %) vs. 43 °C (66.7 %); P > 0.05]. HS significantly increased HSP-70 average concentrations for both breeds at 43 °C. A significant effect was observed for the breed by temperature interaction (P < 0.05) caused by a greater difference between Pelibuey and Suffolk at 43 °C (2.85 vs. 0.53 ng/mL, respectively; P < 0.05) than at 37 °C (0.05 vs. 0.03 ng/mL, respectively; P > 0.05). In conclusion, Pelibuey sheep show more effective body temperature regulation under conditions of environmental hyperthermia. Also, cell viability after HS was higher in Pelibuey than in Suffolk, an effect that could be mediated by an HSP-70-related mechanism.

Effects of summer heat stress on physiological variables, ovulation and progesterone secretion in Pelibuey ewes under natural outdoor conditions in an arid region

“…This discrepancy in results could be attributed to the fact that wool breed ewes were mainly used in these previous studies (breeds not adapted to warm climates); meanwhile, in the present study hair breed sheep were used (adapted to HS). Compared with wool breeds, hair sheep breeds have showed enhanced thermoregulatory mechanisms which allow them a greater tolerance to increasing environmental temperatures (Tabarez-Rojas et al 2009;Romero et al 2013). Other possible reasons for the lack of HS effect on the presence of estrous and ovulation in Pelibuey ewes may be the low number of animals used; consequently similar studies involving larger sample sizes should be carried out to confirm our findings.…”

“…Some studies state that, compared with wool breeds, hair sheep breeds can easily adapt to high environmental temperatures because they tend to reduce their metabolic heat production and their breathing is slower and deeper (Ross et al 1985;Romero et al 2013); likewise, they have high synthesis of heat shock protein-70 in their cells (Romero et al 2013). Results of this study suggest that the elevated respiratory rate may operate as a physiological adaptation mechanism to dissipate body heat in thermal-stressed Pelibuey ewes.…”

“…Previous For live weight and body condition score, no differences (P > 0.05) were observed between the initiation and termination of the experimental period each season. studies done in hair (Neves et al 2009;Tabarez-Rojas et al 2009;Romero et al 2013) and wool (Marai et al 2007;Alhidary et al 2012) breeds also indicated an increase in average values of these physiological variables because of the high environmental temperatures. Increased rectal temperature by HS effect was attributed to the body heat gain from the elevated environment temperatures and metabolic heat production, while the result of respiratory frequency reflects a physiological adjustment done by ewes to dissipate the excess body heat (Silanikove 2000).…”

Role of Heat Shock Proteins in Livestock Adaptation to Heat Stress

“…[45][46][47][48] In farm animals, elevation in HSP70 and HSP90 was observed in sheep, buffalo, cattle, broilers and goats. 11,49,50 The highest level of plasma HSP70 and PBMC HSP70 mRNA transcript expression was reported in Osamanabadi goats exposed to heat and nutritional stress as compared to the control goat which was maintained in the shed and fed ad libitum.…”

Biological responses of feedlot cattle to heat load

“…Additionally it is well supported that the heat tolerance of tropically adapted breeds, i.e. Bos indicus, extends to the cellular level (Hansen, 2004;Basiricò et al, 2011;Romero et al, 2013).…”