Published literature regarding the effects of heat stress on food
intake of cattle is confusing. Worstall and Brody (1953) report that
forage intake of Bos indicus heifers was reduced when these cattle
were exposed to ambient temperatures of 35 °C; Allen et al. (1963)
reported that Bos indicus heifers did not decrease their intake of food
at 39 °C; Brody et al. (1955) reported that a diurnal temperature
variations between 21 °C and 38 °C had no effect on the food intake of
Jersey cows Rogerson (1960) on the other hand reported that ambient
temperatures of 40 °C depressed the food intake of Zebu cattle (Bos
indicus) Hereford cattle (Bos taurus) and cross-bred cattle. The explanation
for these different results is probably found in differences
associated with the experimental design, such as diet, acclimation
periods and duration of experiment. We present here the results of a
comparative study covering a series of different ruminant species
(non-domestic and domestic; arid adapted and non-arid adapted) and
investigated under varying conditions relating to dehydration and
exposure to heat stress. From these studies, it is clear that the food
intake of cattle and goats was depressed following exposure to an
intermittent heat load at 40 °C temperatures, while the food intake of
the other species was not affected. During these treatments all the
experimental animals showed a slight increase in body temperature
(of between 2–3 °C). This temperature lability resulted in storage of
heat. They did not however become hyperthermic.