Feed Intake Response to Changes in Environmental Temperature and Dietary Energy in Roosters

Abstract

The objective of this study was to determine the response characteristics of feed intake following an abrupt change in environmental temperature or dietary energy. A 2 x 2 factorial design was used with 23 and 30° C. environmental temperatures and dietary energy levels of 200 and 300 kcal. metabolizable engery (M.E.) per 120 gm. feed. Five months old roosters were maintained in individual cages. After receiving the treatments for seven months the environmental temperatures were abruptly switched (23 to 30 and 30 to 23° C). Eight weeks later the diets were abruptly switched (200 to 300 and 300 to 200 M.E. kcal.).Significant differences in feed intake due to environmental temperature and dietary energy existed prior to the switches. The switch of environmental temperatures resulted in an immediate inverse change in feed intake. The magnitude of the difference due to temperature was less after the switch than before. An immediate inverse change in feed intake also resulted when the diets were switched. However, in this case the magnitude of the difference due to diet was almost the same after the switch of diets as before. Thus, abrupt changes in dietary energy caused a more marked and precise response in feed intake than abrupt changes in environmental temperature. From this study it was concluded that the thermostatic and chemostatic mechanisms exert control over feed intake not only on a short term basis but also to some extent on a long term basis. With the temperature and dietary energy treatments used in this study, the effect of the chemostatic mechanism was more pronounced than the thermostatic mechanism in controlling feed intake. Heat increment of the feed appeared to be more involved with the cessation than the initiation of feeding.