The effects of chronic exposure to elevated environmental temperature on intestinal morphology and nutrient absorption in the domestic fowl ( Gallus domesticus)

Abstract

1. 1. Exposure of growing broiler chickens to elevated environmental temperature (35°C) for two weeks, markedly reduced food intake (29%) and growth rate (37%) compared to birds maintained at 22°C. 2. 2. These changes in growth were accompanied by increased in vivo jejunal uptakes of galactose (36%) and methionine (50%) measured per unit intestinal dry weight. 3. 3. Both the electrogenic (phloridzin sensitive) and non-electrogenic (phloridzin insensitive) components of galactose absorption were increased by 24 and 52% respectively during the chronic heat stress. 4. 4. The size of the absorptive compartment may be reduced by the heat stress as reflected by decreased villus heights (19%) and wet (26%) and dry (31%) weights per unit length of jejunum. 5. 5. It is suggested that the changes in hexose and amino acid during chronic exposure to elevated ambient temperature may reflect adaptations to optimise nutrient absorption in the face of reduced nutrition and decreases in the size of the absorptive compartment. A functional hypothyroidism (plasma luminal T3 decreased by 66%) associated with heat stress may contribute to the observed alterations in jejunal structure and function.