Cows, as well as other animals, are naturally cooled by evaporation, radiation, respiration, convection, and conduction. Dairy cows, in particular, attempt to maintain desired core temperatures through the processes of evaporation (skin), respiration (breathing), radiation (emittance), convection (transfer of thermal energy by air movement), and conduction (contact between surfaces where one surface has a higher thermal energy level than the other surface).
Evaporation as a means to release excess thermal energy is dramatically limited by the surrounding humidity. When humidity levels are high, there is little range for evaporation of water, whether excreted through the skin, on the tongue, or from application of water to the animal, i.e. soaker and misting systems that apply water on the animal and which are commonly used in most dairy operations. Under conditions of humidity saturation, there can be no effective evaporation.
Respiration can expel thermal energy via the elevated temperature of the exhaled air and its moisture. However, under conditions of high temperature, the inhaled air can actually increase the heat intake of the animal (air over critical core temperature of 101.5° F. to 103° F.). Again, in a near or saturated humidity condition, the benefit of evaporation in conjunction with the breathing is severely limited from the animal's lungs.
Radiation as a means to expel excessive core heat is limited in conditions where the cow is either confined full-time or the cow is outside where there is typically not a clear night sky for energy to radiate from the animal to a body of lower energy. In fact, in many animal confinement structures the major radiation that occurs is from the daytime higher temperature of the underside of the roof to a cooler surface, the animal. This is illustrated by metal roofing for a dairy barn that can easily reach 160° F. in summer periods, while the dairy cows in question have a lower energy level of the normal skin temperature of approximately 99° F. This means the cows are receptors of energy, not emitters. Clouds and high humidity, as well as being indoors, can severely limit any ability for a cow to radiate energy.
Convection, or cooling by air movement over the animals, is limited by the temperature of the moving air, the animal in question, grouping of the animals, distance from the air movement equipment, and other internal building design constraints. If the air is at or above the desired surface skin temperature, there is no beneficial direct energy transfer. Close crowding of animals defeats convection transfer, i.e. no air movement over the higher thermal energy surface, means no transfer. In fact, still air has an assigned insulating or thermal resistance value (R-Value).
In most dairy operations, cows are housed in confinement structures called ‘free stall barns’. In geographical areas where the average air temperatures are high, these barns are typically open on the sides and ends to provide for air circulation. However, during periods of high temperature and/or humidity, the cooling effects on the animals through evaporation, radiation, respiration, and convection are severely limited.
As is well known to those in the industry, the most common method used in dairy operations to abate the effects of heat stress on their animals is to install fans to circulate air as well as water soaking and/or misting systems. Current evaporative and convective systems (fans or other air movement means) for the auxiliary cooling of confined animals have severe limitations due to the effects of the local wet bulb temperature, ambient temperature, and the ability for artificial convective cooling to supplement the natural processes of the subject animal.
Moreover, utilizing fans and misting to cool dairy cows and other confined animals during the summer months places a large demand for electricity during the peak operational hours on the power grid, as well as placing a large demand on the water source for the various soaking and misting system operations. The associated high energy costs and high water usage of this type of animal cooling, which in some states is becoming cost-prohibitive, has resulted in an urgent need for an alternative method of cooling livestock during weather above the desired ambient temperature (68° F. for cows). Additionally, conventional cooling has severe limitations to the available heat transfer pathways used by animals.
Moreover, conventional cooling methods for dairy cattle utilizing fans and misting/soaking during the summer months cause inherent health problems with the cattle. A wide range of research has proven that as a direct result of misting and soaking for cattle cooling purposes, the incidence of mastitis and lameness of dairy cattle significantly increases during the summer months. This results in lost milk production and/or involuntary culling of problematic cattle resulting in a significant financial loss. The economic consequences to dairy producers from heat stress conditions can be lost milk production, poor reproductive performance, and increased health problems. Therefore, there is a need for an improved means of cooling livestock in animal farm operations that significantly reduces these associated health problems as a direct result of the conventional cooling methods currently in use
Moreover, in areas with severe cold weather conditions, there is a significant requirement and desire to be able to provide supplemental heat to the animal to maintain food-to-output ratios in a profitable range. Excessive cold conditions lead to physical impacts to dairy cows, including freezing of teats, that leads to severe losses in milk production as well as overall health. Although there are known systems for providing supplemental heat to animal confinement facilities, this invention provides a simple supplemental heating and cooling system.