The long-term goal is to develop the knowledge and tools the cattle industry will use to increase tolerance to heat stress while simultaneously allowing for increased efficiency of production, reproduction, and meat quality. The strategy we propose is to reveal the genetic architecture of traits defining thermal tolerance and productivity in indicine influenced cattle. It is critically important to identify functional variants contributing to thermotolerance without a negative pleiotropic effect on production-fertility related traits. This will allow genomic selection within breeds for superior productivity under hot and humid conditions.Objective 1. Thermotolerance phenotype collection to identify heifers with high and low thermotolerance measures.Objective 2. Determine the nature and magnitude of the genetic and phenotypic relationships between thermotolerance, feed efficiency, and reproductive performance.Objective 3. Identify key-regulator variants for thermotolerance with positive or no pleiotropic effect on production traits using functional genomics in a systems biology approach.Objective 4. Generate whole-genome sequence and gene expression data to define the transcriptome and identify DNA variation for increased heat exchange ability.