Temperature Humidity Index for Growing Tom Turkeys

Temperature-humidity effects on physiological responses of tom turkeys were investigated using a twodimensionalrotatable central composite design. Eight temperature-humidity combinations were evaluated from 23 to40C and 40 to 90% RH. Response surfaces for mean, variation, and slope of core body temperature, CO2 production,and moisture production were used to assess level of stress at each of four ages. Temperature and humidity wereapproximately equal in their effects on physiological responses of 6-wk-old turkeys. Above 10 weeks of age, temperaturedecreased in relative significance as a stressor, and humidity appeared to be a more important factor in the birds abilityto maintain homeothermy.