Invited review: Physiological and behavioral effects of heat stress in dairy cows

Abstract

Animal welfare can be negatively affected when dairy cattle experience heat stress. Managing heat stress has become more of a challenge than ever before, due to the increasing number of production animals with increased milk yield, and therefore greater metabolic activity. Environmental temperatures have increased by 1.0°C since the 1800s and are expected to continue to increase by another 1.5°C between 2030 and 2052. Heat stress affects production, reproduction, nutrition, health, and welfare. Means exist to monitor and evaluate heat stress in dairy cattle, as well as different ways to abate heat, all with varying levels of effectiveness. This paper is a summary and compilation of information on dairy cattle heat stress over the years.

Heat stress on microbiota composition, barrier integrity, and nutrient transport in gut, production performance, and its amelioration in farm animals

“…Moreover, a threat in global rise of environmental temperature has compelled research for better understanding of HS response mechanisms of animals and its mitigation. High environmental temperatures adversely affect the well-being, production and welfare of animals [3,4]. Overall, production performances of all types of livestock species including poultry are adversely affected by HS due to decreased feed intake with reduced nutrient utilization and feed efficiency resulting in considerable economic losses [5,6].…”

“…Heat stress in animal production systems can cause alterations in the normal microbial communities and epithelial structures in the intestine, which may lead to greater colononization of pathogenic and undesirable microbiota [12]. There are many reviews focusing biochemical, cellular and metabolic changes that occur during thermal stress [13], production performance and welfare [2,14,15] along with HS mitigation strategies [3,4]. This review mainly focuses on the effect of HS on gut microbiota composition and intestinal health including mucosal morphology, barrier and nutrient transport functions, immunity and antioxidant status in the intestine with some discussion on the production performance and dietary HS mitigation strategies in livestock and poultry.…”

Automated Monitoring of Panting for Feedlot Cattle: Sensor System Accuracy and Individual Variability

“…Heat stress has been traditionally monitored using the visual assessment of an animal’s response evoked by high ambient temperatures and 25 °C has been suggested as a threshold after which both dairy [ 15 ] and beef [ 16 ] cattle experience heat stress. However, a threshold of 22 °C [ 17 ] has also been suggested for feedlot cattle.…”

Recent Advances on Early Detection of Heat Strain in Dairy Cows Using Animal-Based Indicators: A Review

“…Cows can maintain a balance of heat production and heat dissipation in the thermoneutral zone (TNZ), in which cows perform the lowest physiological and immune costs, and the highest productivity [1]. When the thermal environment exceeds TNZ and suppresses the efficiency of non-evaporative heat loss, evaporative heat loss, or both [3,4], various mechanisms are activated in dairy cows to dissipate excess heat and maintain homeothermy [5]. In the present review, "heat stress" represents the sum of external stressors, forcing the animal to exceed its TNZ.…”

“…However, production loss is more likely a result of heat strain than an early indicator [7] and usually lags the changing environment by about two days [16,17]. In fact, heat strain includes both short-and long-term responses from vasodilation that happens instantly to gradual physiological adaptation [1,5]. Recently, many efforts have been made to use more sensitive physiological indicators to help detect heat strain in the early stage [18,19].…”