Production loss due to heat stress is a major concern in the livestock industry. Dairy cattle are especially susceptible to heat stress. Milk production loss due to heat stress accounted for about 1.2 billion dollars in 2010 (Lundeen, 2014). Heat stress occurs when combinations of environmental parameters (temperature, airspeed, relative humidity, etc) reach levels where the animal struggles to release internally produced heat. Implementing mitigation strategies to reduce heat stress has been a crucial need as dairy housing has transitioned from pasture to indoor housing systems.

Currently, limited recommendations exist directing producers towards implementing one cooling system over another, specific to the climate in their region. In order to maximize production, producers need the most optimal cooling system in their operation in order to reduce heat stress. To assist producers in heat stress mitigation decision making, a thermal interaction model was developed to quantify heat dissipation from a dairy cow’s core to her surrounding environment using procedures and parameters from published thermal balance models. Environmental input parameters used for the model were taken from typical meteorological year (TMY3) data sets.

The objectives of this research were to: (i) analyze the thermal environment’s ability to reduce heat stress in dairy cattle in selected regions using TMY3 data, (ii) model Holstein cattle subjected to evaporative cooling + airspeed, and direct water sprinkling + airspeed cooling systems by region, (iii) create a universal barn/cooling system model to apply to selected regions with given TMY3 data inputs, and (iv) develop contour maps with optimal cooling system recommendations throughout the United States.

A thermoregulation model was developed combining equations from previous models to analyze a cow in her ambient environment in a barn to determine if she is heat stressed using various cooling strategies. The model was tested in two stations in California (SN:723890) and Wisconsin (SN:726435). The model’s predictions were within one standard deviation of field data. Once the model was validated, the model was ran for all 215 TMY3 Class 1 stations and contour maps of the U.S. were created for producers to determine which cooling strategy is the most economical in their region.

The results from this work show that CCI is a better thermal index than using THI and that the MVCE and LVCE cooling strategies are the most economical cooling strategy for dairy cattle housing when the milk price is fixed at $0.363 kg-1, water price is fixed at $0.0015 gallon-1 and energy cost is fixed at $0.12 kW-hr-1. Multiple maps were made for each of the eight cooling strategies that producers can use with a developed equation to determine which cooling strategy is the most economical for their region.