Heat Stress in Dairy Cattle: Major Effects and Practical Management Measures for Prevention and Control

Abstract

Open Access Review Article ways by which animals can get rid of their thermal body load: conduction, convection, radiation (Figure 1). In the zone I-III the animal can maintain a constant body temperature; in zone I-II and zone II-III heat production and heat loss is regulated. In zone I-II, heat production increases in order to maintain homeostasis. Zone II-III is the thermo-neutral zone, where heat loss is kept constant. Factors other than climate (e.g. ration, milk yield level, activity) determine the heat production in that zone [2]. The temperature points II and III are the lower and upper critical temperatures respectively, beyond which cold stress and heat stress respectively occur. When temperature increases beyond a given critical limit, the non-evaporative ways of heat loss appear to be far less efficient. And if temperature rises even more, the cow changes from a non-evaporative to an evaporative way. However, the latter is strongly dependant on the level of air humidity. The thermo-neutral zone of dairy cows in full lactation is, roughly speaking, between-5°C and +20°C for adult dairy cows Abstract Over the past years we have experienced several periods of heat waves, sometimes of short, other times of longer duration. This phenomenon will, most probably, be more frequent in the years to come. Heat waves may have detrimental effects on cattle production, health, welfare and reproduction. The question is whether cattle farmers and even veterinarians are sufficiently prepared and instructed to counteract or, even better, prevent the negative effects of heat stress in their cattle. This paper reviews the most relevant issues associated with the occurrence of heat stress, and provides practical measures to counteract and prevent the negative effects of heat stress in cattle.