Are locally adapted goats able to recover homeothermy, acid-base and electrolyte equilibrium in a semi-arid region?

摘要

The objective of this study was to evaluate the thermoregulatory responses, acid-basic and electrolytic equilibrium of locally adapted goats under natural heat conditions in a semi-arid region. Ten (10) Caninde goats aged between 2 and 3 years, non-lactating, non-pregnant and having a body weight (B-w) of 22.90 +/- 2.70 kg were used in this study. Air temperature (A(T)) and relative humidity (R-H) were measured, and the radiant heat load (RHL) was subsequently calculated. Rectal temperature (R-T), respiratory rate (R-R), sweating rate (S-R) and heat shock (S) were recorded at 1-h intervals for 24 continuous hours. Hydrogen potential (pH), partial pressure of carbon dioxide (PCO2), partial pressure of oxygen (PO2), bicarbonate (HCO3), base excess (BE), total carbon dioxide concentration (TCO2), oxygen saturation (SO2), sodium (Na+) and potassium (K+) were recorded at three moments during the day (5 a.m.; 1 p.m.; 6 p.m.). There were also significant differences between the means of hours of the day for A(T) and R-H. R-R was the thermoregulatory response which most closely followed RHL, with important elevations in the periods between 10 a.m. to noon. It was observed that the goats activated their SR mechanism before R-R, more precisely between the hours of 9 a.m. and 1 p.m. The acid-base and electrolytic equilibrium for the goats which showed great association with the first components contributed the most to the total variation of the data. The most important variables in the adaptive profile of these animals in order of importance were: SO2, PO2, R-R, R-T, S-R, HCO3, BE, TCO2 and pH. An association between all variables grouped in each period was observed, where the thermoregulatory responses in the periods of 5 a.m. and 6 p.m. were closer than when compared to 1 p.m., showing a physiological return to the initial state. Therefore, the variation in thermoregulatory responses, acid-base and electrolytic equilibrium indicated that the goats have the ability to recover after a challenging environmental condition.