The US dairy industry loses millions of dollars every year due to problems associated with high heat load such as reduced milk production and cattle mortality. Although dairy farmers provide their cattle with heat abatement resources (shade, sprayed water, fans), economic losses associated with heat load indicate a problem is ongoing in the US dairy industry, suggesting the strategies used are not effectively cooling the cows. In fact, little is known about how heat abatement resources are provided in commercial situations (i.e., quantity and quality), nor their effectiveness. Thus, identifying dairy cattle experiencing high heat load and adopting appropriate mitigation strategies can lead to improvements in animal welfare and profitability. In addition to finding more effective heat abatement strategies for cattle, changes in weather patterns have raised concerns about the use of potable water in agriculture. In the US, 75% of the large dairies use sprayed water to relieve heat load during summer. The widespread use of water indicates that there are opportunities to improve the efficiency of water use and cow cooling. Aspects of spray management (i.e., flow rate, temperature threshold the spray is activated and timing) can affect the quantity of water used; however, their effects of cooling effectiveness are variable. For example, using higher flow rates increases water use but that does not necessarily translate into more cooling. Manipulating timing has a potential to affect water use and cooling effectiveness – as it is connected to how the spray cools the cows. The objectives of this dissertation were to describe the provision of heat abatement resources as well as behavioral and physiological responses to heat load in commercial dairies, and to evaluate the cooling effectiveness of different spray strategies. In Chapter 1, I investigated the accuracy of sampling strategies to measure responses to heat load in lactating cows during the warmest part of the day. In this study, I found that behavioral and physiological responses can be sampled as often as every 30 min without compromising the accuracy of results. In Chapter 2, I describe the diversity of provision of heat abatement resources and cattle responses to heat load on 10 commercial dairy farms in CA. The results of this assessment indicated that some CA dairies were doing well while others faced challenges. Respiration rates, for example, could be as low as 65 to as high as 95 breaths/min and were positively related to inactivity. In addition, the quantity of water used to spray cows ranged from 0 to 25.6 liters/h per cow and it was a product of different flow rates, spray timing and cow:nozzle ratio. Chapters 3 to 5 evaluate the effects of different spray timing strategies on cow cooling. First, I tested the effects of time on and off, thus, strategies varying in quantity of water use, in restrained cattle. Next, I evaluated the combined effects of different flow rates and timing (using the same water volume) on behavior, physiology and production in cows housed in a freestall barn. Spraying cows for longer (Chapter 3 and 4) or reducing time off (Chapter 4), thus, using more water, reduced heat load more effectively in cattle than strategies that required less water (2.5 vs. 64 L of water per application, Chapter 3; 20 vs. 33 L of water/h per cow, Chapter 4). When spraying cows the same quantity of water, timing did not affect cooling effectiveness (Chapter 4 and 5). On the other hand, using a higher flow rate (22 vs. 33 L of water/h per cow), tended to improve cow cooling and milk production. However, these differences were small and their biological relevance is unclear, especially in this situation, where all cows were relatively cool. My dissertation has provided insight into heat abatement in dairy cattle: methodology to study it, the range of provision on commercial farms and new information about how spray management affects dairy cattle behavior and physiology. Happily, I have identified clear ways to mitigate heat load in arid, hot conditions, but the challenge about how to reduce water use, while still ensuring that cows are cool, remains.

The objective of this research was to design and test a novel conductive cooling system for controlling heat stress in lactating dairy cows by circulating chilled water through modified DCC waterbeds (Dual Chamber Cow Waterbeds). The system was tested to determine (1) the heat flux between the cooled waterbeds and the cows; (2) the production benefit to heat-stressed dairy cows; (3) the sensitivity of moisture accumulation and heat flux to type and thickness of bedding; and (4) the potential economic benefit. The calculated heat flux of the system was 439 W/m2 when the temperature of the circulating water in the waterbeds was 4.5oC and was 382 W/m2 when the circulating water temperature was 10.0oC. This was for live cows and about 1 cm of sawdust bedding. This amount of heat flux is significant compared to the amount of metabolic heat a lactating cow must lose. Conductively cooling the cows with 4.5°C water decreased core body temperature by 1.0°C (p

Environmental stress is one of the most significant factors affecting livestock performance and health, and it is only expected to increase with effects of global warming. Environmental Physiology of Livestock brings together the latest research on environmental physiology, summarizing progress in the field and providing directions for future research. Recent developments in estimating heat stress loads are discussed, as well as key studies in metabolism, reproduction, and genetic expressions. Environmental Physiology of Livestock begins with a survey of current heat indexing tools, highlighting recent discoveries in animal physiology, changes in productivity levels, and new technologies available to better estimate stress response. Using this synopsis as a point of orientation, later chapters hone in on major effects of heat stress, including changing metabolic pathways and nutrient requirements, endocrine regulation of acclimation to environmental stress, and reduced reproductive performance. The text concludes with a thorough discussion of environmental effects on gene expressions, providing important insight for future breeding practices. Environmental Physiology of Livestock is a globally contributed volume and a key resource for animal science researchers, geneticists, and breeders.

This lively book examines recent trends in animal product consumption and diet; reviews industry efforts, policies, and programs aimed at improving the nutritional attributes of animal products; and offers suggestions for further research. In addition, the volume reviews dietary and health recommendations from major health organizations and notes specific target levels for nutrients.

Two strategies to reduce impact of heat stress on high producing dairy cows were examined. The first was to recalculate the temperature-humidity index (THI) using high producing dairy cows under diurnal summer conditions. This re-evaluation confirmed that current THI values underestimate the severity of heat stress levels. Therefore, cooling of dairy cattle during warm summer months should begin at a THI of 68.A second objective involved three studies carried out to evaluate use of niacin in dairy cow rations to improve evaporative heat loss and resistance to heat stress. Niacin is known to cause intense vasodilation in human and lab species. We hypothesized that increasing vasodilation would improve evaporative heat loss in dairy cows. In the first niacin study, supplementation of lactating dairy cows with an encapsulated rumen by-pass form of niacin (NIASHURETM; Balchem Corporation, New Hampton, NY) and proved effective in alleviating some affects of heat stress during mild thermal stress. This was observed through increased evaporative heat loss, increased water intake to support the increased sweating rate, decreased rectal and core temperatures. Past research demonstrated that the possible mechanism for vasodilation affects seen by niacin were most likely due to prostaglandin D secretions. Niacin apparently may act through increased prostaglandin D and E production and secretion by Langerhans cells which then act upon vascular endothelial prostaglandin D receptors to increase vasodilation. Additionally, we and others have now shown that these prostaglandins induced elevated heat shock protein gene expression leading to improved cellular viability under heat stress conditions (42 ðC). No studies have evaluated impact of encapsulated niacin on milk yield and composition during periods of thermal stress under commercial dairy conditions. Therefore, the objective of the last study was to examine the effects of encapsulated niacin during heat stress on milk production and composition as well as core body temperatures under commercial conditions. We concluded that feeding encapsulated niacin did reduce body core temperature but did not increase daily milk yields; however, milk fat and protein percentages were increased thereby, increasing 4% fat- and energy-corrected milk yields significantly when animals were fed encapsulated niacin.

Dr. Anjali Aggarwal is working as a Senior Scientist at National Dairy Research Institute, Karnal (India). She holds a PhD degree in Animal Physiology and is involved in research and teaching at post-graduate level. Her area of research work is stress and environmental physiology. She has more than 50 publications, two technical bulletins, four manuals and many book chapters to her credit. She has successfully guided many post-graduate and PhD students. Her major research accomplishments are on microclimatic modification for alleviation of heat and cold stress, mist and fan cooling systems for cows and buffaloes, and use of wallowing tank in buffaloes. Her work involves the use of technology of supplementing micronutrients during dry period and early lactation to crossbred and indigenous cows for alleviating metabolic and oxidative stress and improved health and productivity. Studies are also done in her lab on partitioning of heat loss from skin and pulmonary system of cattle and buffaloes as a result of exercise or exposure to heat stress. Dr. R.C. Upadhyay is working as Head, Dairy Cattle Physiology Division at National Dairy Research Institute, Karnal (India). He graduated in Veterinary Sciences and obtained his PhD degree in Animal Physiology. His area of recent research is climate change, stress, and environmental physiology. His major research accomplishment is on climate change impact assessment of milk production and growth in livestock. His work also involves studying methane conversion and emission factors for Indian livestock and use of IPCC methodology of methane inventory of Indian livestock. Heat shock protein-70 expression studies in cattle and buffaloes are also done in his lab. Draught animal power evaluation, fatigue assessment, work-rest cycle and work limiting factors form the highlights of his work. Studies on partitioning of heat loss from skin and pulmonary system of cattle and buffaloes and electrocardiographic studies in cattle, buffalo, sheep and goat are also undertaken in his lab. He has more than 75 research papers, four books and several book chapters to his credit. Technologies developed and research done by him include methodology of methane measurement: open and closed circuit for cattle and buffaloes; inventory of methane emission from livestock using IPCC methodology; livestock stress index: thermal stress measurement based on physiological functions; and draught power evaluation system and large animal treadmill system. He received training in Radio-nuclides in medicine at Australian School of Nuclear Technology, Lucas heights, NSW, Australia in 1985 and Use of radioisotopes in cardiovascular investigations at CSIRO, Prospect, NSW, Australia, during 1985-86. He has guided several post-graduate and PhD students. He is recipient of Hari Om Ashram Award-1990 (ICAR) for outstanding research in animal sciences.