About this webinar

Recorded On: Wednesday, March 25, 2020

Presented By: Kaitlyn Sarlo Davila, Ph.D Candidate at The University of Florida

Heat stress is a major limiting factor of beef cattle production. Over 40% of the world’s beef cattle reside in tropical or subtropical climates known for their hot and humid conditions. When cattle experience heat stress they exhibit lower feed intake, reduced pregnancy rates and in extreme cases even death. In the U.S. alone, heat stress results in a loss of $369 million a year due to reduced animal performance. The overall goal of this project is to develop genomic tools to select for animals with superior thermal adaptation.

In order to unravel the genetic architecture underlying heat tolerance this project utilizes 2,800 animals from a Bos indicus and Bos taurus crossbred population. Thermotolerance is a quantitative trait controlled by many genes and under environmental influence and it is also difficult and expensive to measure. These challenges can be overcome by collecting precise phenotypes on many of the underlying traits that contribute to an animal’s thermal adaptation. Under heat stress, cattle primarily lose heat via cutaneous evaporation at the skin-hair coat interface. Many factors affect the efficiency of evaporative cooling including sweating capacity, sweat gland properties and hair coat properties. This project not only measured continuous core body temperature of cattle in the crossbred population under low, average, and high heat stress conditions using iButton technology but also measured sweating rate and collected skin biopsies and hair samples. The skin biopsies were processed into histology slides, from which dermis thickness, sweat gland size, sweat gland number and sweat gland depth were measured. Hair samples were measured for length and diameter. These skin and hair properties have been found to have significant effects on the core body temperature under heat stress.

Once thermotolerance had been described by these precise phenotypes, the genetic variants underlying these traits were characterized using genome wide association studies (GWAS) utilizing SVS. Several promising selection candidates have been identified for the hair traits through these methods. We intend to leverage the SVS software to also identify selection candidates and putative functional mutations for skin properties and ultimately perform a meta-analysis on the results of the multiple GWAS to determine the relationship of the sub phenotypes of thermotolerance to each other and also to other pertinent beef production traits.