Feed form and nutritional level for rearing growing broilers in thermoneutral or heat stress environments

Many endurance athletes perform specific blocks of training in hot environments in “heat stress training camps.” It is not known if physiological threshold heart rates measured in temperate conditions are reflective of those under moderate environmental heat stress. A total of 16 endurance-trained cyclists and triathletes performed incremental exercise assessments in 18°C and 35°C (both 60% relative humidity) to determine heart rates at absolute blood lactate and ventilatory thresholds. Heart rate at fixed blood lactate concentrations of 2, 3, and 4 mmol·L−1 and ventilatory thresholds were not significantly different between environments (P > .05), despite significant heat stress-induced reductions in power output of approximately 10% to 17% (P < .05, effect size = 0.65–1.15). The coefficient of variation for heart rate at these blood lactate concentrations (1.4%−2.9%) and ventilatory thresholds (2.3%−2.7%) between conditions was low, with significant strong positive correlations between measurements in the 2 environments (r = .92–.95, P < .05). These data indicate heart rates measured at physiological thresholds in temperate environments are reflective of measurements taken under moderate environmental heat stress. Therefore, endurance athletes embarking on heat stress training camps can use heart rate–based thresholds ascertained in temperate environments to prescribe training under moderate environmental heat stress.

Download Full-text

Raising productivity of cereal crops in dry and heat stress environments remains a breeding challenge.

CAB Reviews Perspectives in Agriculture Veterinary Science Nutrition and Natural Resources ◽

10.1079/pavsnnr202116008 ◽

2021 ◽

Vol 16 (008) ◽

Author(s):

Sangam L. Dwivedi

Keyword(s):

Heat Stress ◽

Agricultural Production ◽

Green Revolution ◽

Cereal Crops ◽

Plant Genes ◽

Stress Environments

Abstract 'Green Revolution' genes have led to the release of input-responsive cultivars, resulting in multifold productivity increases in rice and wheat. Declining precipitation, increased intensity of drought and rising temperature are casting uncertainty over agricultural production. As noted in this mini review, plant genes when over-expressed allow cereals to produce grains in drought- and heat-prone sites.

Download Full-text

Computer Simulation of Thermoregulatory Responses to Heat Stress: A Future Work Design and Training Tool

Proceedings of the Human Factors Society Annual Meeting ◽

10.1177/107118137702100212 ◽

1977 ◽

Vol 21 (2) ◽

pp. 142-146

Author(s):

Jerry R. Duncan

Keyword(s):

Heat Stress ◽

Skin Temperature ◽

Absolute Difference ◽

Mean Skin Temperature ◽

Body Segment ◽

Minute Exposure ◽

Blood Flows ◽

Thermoregulatory Responses ◽

Stress Environments ◽

And Task

A mathematical model of human thermoregulation was developed to simulate thermoregulatory responses of man exposed to heat stress environments. The model was validated with experimental results of a man pedalling in environments of 35 and 45°C dry-bulb and 33 mm Hg water vapor pressure. The model inputs of body segment temperatures, thermal characteristics, basal blood flows, basal heat production, and of environmental and task characteristics permitted the model to be “individualized” for a specific subject, environment, and task. The model outputs of body segment temperatures, blood flows, and sweat loss at designated intervals permitted observation of the dynamic thermoregulatory responses over a 60 minute exposure period. The model was successful in predicting the change in thermal responses of a clothed man working in heat stress environments. Over the 60 minute exposure at 45°C the mean absolute difference between experimental and simulated values of head skin temperature was 0.28°C. The difference for trunk mean skin temperature was 0.12°C; for body mean skin temperature, 0.29°C; and for internal body temperature, 0.53°C.

Download Full-text