The effect of both environmental and management related stressors on fertility is discussed. While environmental heat as a stressor is significant in disrupting normal reproductive cyclicity, management induced stress is becoming more important when related to the requirements of modern production methods. Deviations in hormonal patterns are noted, and the clinical manifestations brought about by these changes are described. Since reproduction is the ultimate measure of an animal's ability to adapt to an ever changing external milieu, as well as forming the basis of life-time productivity, research should be aimed at obtaining greater clarity of the hormonal interactions involved. The role of neurotransmitters in these physiological mechanisms should not be overlooked. Psychobiological studies must be extended so as to provide a positive input into management procedures that should be used in intensive production units for optimal fertility and productivity.