Effects of Tasco in Alleviation of Heat Stress in Beef Cattle

A study was conducted to evaluate the influence of Ascophyllum nodosum (Tasco) on rectal temperature, respiration rates, and in situ NDF disappearance in cattle exposed to elevated ambient temperature. Twenty-four Angus crossbred steers (average BW = 300.6 kg) were randomly assigned to treatments using a 2 × 2 factorial arrangement: 1% Tasco vs. no Tasco (control), and thermoneutral (TN) vs. heat load (HL) conditions. Three steers in each room were assigned to the Tasco vs. control treatment. In period 1 (10 d), steers were acclimated to chambers at TN (19°C) conditions. Subsequently, for periods 2 and 3, HL was maintained at a daytime high of 36°C and a nighttime low of 19 and 31°C, respectively. For period 4, temperature conditions (TN and HL treatments) were reversed and period 2 HL conditions were imposed. In periods 2 (P < 0.09) and 4 (P < 0.05), Tasco lowered DMI. In period 2, the control steers had greater (P < 0.0001) differences between maximum and minimum rectal temperatures than steers in the Tasco treatment; this difference occurred between d 4 and 8 for the HL group. In periods 2 and 3, the maximum and minimum differences in respiration rate values were greater (P < 0.05) under HL conditions for the Tasco vs. control treatment. In period 4, the maximum respiration rate response to HL tended to be greater (P = 0.07) under HL conditions for the control vs. Tasco treatment. In period 2, a trend existed for steers in the Tasco treatment to have a greater (P < 0.1) rate of in situ NDF disappearance than control steers. In conclusion, Tasco appeared to reduce rectal temperature for 3 to 4 d.