Aldosterone and ADH response to heat and dehydration in cattle

Abstract

The effect of heat (35 degrees C) and dehydration under heat (30 h) on plasma levels of antidiuretic hormone (ADH) and aldosterone was studied on four nonpregnant dry Holstein cows. Heat exposure caused a rapid significant rise in plasma ADH without significant changes in hematocrit (Hct), small but significant increase in urine output and a significant reduction in total plasma protein. Dehydration under heat caused a sharp increase in ADH levels associated with a significant decrease in urine output and a significant increase in plasma protein, blood Hct, and serum osmolality. A significant reduction in plasma aldosterone level was observed after 24 h of heat exposure. This was associated with a slight rise in urinary sodium excretion and a significant reduction in serum sodium. Both serum and urinary potassium concentrations were significantly lower under heat. Dehydration resulted in a slow rise in aldosterone but did not reach thermoneutral level. This is probably due to the inhibitory effect of higher serum sodium observed during dehydration on plasma aldosterone secretion. The rise in ADH and decrease in aldosterone during heat exposure may explain why cattle are one of the few species that do not concentrate urine during heat exposure.

Effect of water restriction and environmental temperatures on metabolic rate and physiological parameters in sheep

“…The trends did reflect fluctuations in blood haemoglobin. To some degree, it is similar to previous reports that dehydration under heat stress resulted in a significant rise in PCV (El-Nouty et al 1980;Igbokwe 1993). However, temperature does not seem to induce major changes in blood PCV, on the basis of the present study and other published research (El-Nouty et al 1980;Igbokwe 1993).…”

“…To some degree, it is similar to previous reports that dehydration under heat stress resulted in a significant rise in PCV (El-Nouty et al 1980;Igbokwe 1993). However, temperature does not seem to induce major changes in blood PCV, on the basis of the present study and other published research (El-Nouty et al 1980;Igbokwe 1993). Hossaini-Hilali et al (1993) reported that haematocrit increased during 48 h starvation in goats, which is not consistent with the present results where there were no significant effects of fasting on blood PCV.…”

“…Dehydration under warm conditions reduced plasma volume as water was taken up by the tissue in mammals (Schaefer et al 1990) and also induced an increase in secretion of aldosterone and cortisol to maintain fluid balance (El-Nouty et al 1980;Schneider 1990). Indices of dehydration include increases of PCV and Hb concentration with increased time off feed and water and plasma osmolality increases in sheep and lactating goats during water deprivation (Laden et al 1987;Dahlborn et al 1988;Olsson and Dahlborn 1989;Abdelatif and Ahmed 1994).…”

Temperatura ambiente e concentrações séricas de cortisol em suínos em crescimento-terminação

“…Normal values were reached after 48 hours, remaining until the end of the stress condition. Other researches verified great decrease 4 or no effect of heat stress on the corticoid levels 5 regardless duration or intensity. This can be an indication of individual inability to regulate cortisol secretion when stress condition is applied.…”

The effect of sudden solar exposure on thermophysiological parameters and on plasma prolactin and cortisol concentrations in male Creole goats

“…3b) (Macfarlane, 1976 ;El Nouty et al, 1980 These results and the thermoregulation failure observed in animals treated with an inhibitor of prolactin secretion at the hottest hours of the day (Berbigier, Sergent, and Ravault, 1985) …”