Cutaneous Moisture Loss in the Bovine during Heat Exposure and Catecholamine Infusion

An experiment was conducted to determine the effect of environmental heat exposure and catecholamine infusion on cutaneous moisture loss, pulse rate and rectal temperature. Five non-lactating Holstein cows housed in climatic chambers were allowed 3 weeks to adjust at 18 C, 50% RH and then exposed to 18 C, 50% RH and 35 C, 50% RH temperature treatments. At each temperature, saline, epinephrine and norepinephrine solutions were infused intravenously for 6 hours. Epinephrine was infused at a dosage rate of 0.25 mcg/kg/ min. At 18 C, epinephrine increased cutaneous moisture loss 300%, pulse rate 29% and rectal temperature 0.8%. At 35 C, epinephrine increased cutaneous moisture loss 55%, pulse rate 20%, but rectal temperature was not affected. The overall analysis indicated the increase in rectal temperature during epinephrine infusion was an environmental temperature effect and the increase in pulse rate a drug effect. The increase in cutaneous moisture loss during heat exposure and epinephrine infusion was explained in terms of the “blood flow-interstitial fluid volume theory”, which was proposed as a mechanism for cutaneous moisture loss in bovines.