Relationship between wool cortisol, wool quality indices, and climatic variables in Australian Merino Rams from Tasmania

Cobb, Troy
University of Queensland


Australia is the largest producer and exporter of fine quality wool globally, and Merino wool is a significant component of the Australian wool and agricultural industry. Stress cortisol affects the quality of Merino wool growth. Stressors that induce cortisol production are centred around nutrition, disease, and thermal triggers, including climatic variations. This study focuses on how these stressors affect Saxon Merino ram wool phenotypes and production performance. Experimental steps analysed the cortisol levels in Saxon Merino ram wool samples using the ELISA process at the UQ Stress Laboratory, Gatton campus, Queensland. This was followed by statistical analysis using Microsoft Excel with the data from the Bureau of Meteorology (BOM) and the stud operator. The first part of Hypothesis 1 was upheld with a p-value of 8.83E-08, indicating non-normality of the data set; this signified that there were variations in the cortisol levels. The data did not support the second part of hypothesis 1. There was a p-value of 0.42, which indicated no statistically significant correlations between total cortisol levels and the price of Merino wool. The first part of hypothesis 2, was not supported; there was a p-value of 0.156 for Chill Index (CI) and cortisol levels. The second part of hypothesis 2 was supported by alignments between El Nino Southern Oscillation (ENSO) and climate conditions in the Tasmania Midlands region. Effects on wool phenotypes from ENSO cycles were considered to contribute to the wool phenotype quality. It was concluded that there was no correlation between cortisol and price index nor cortisol and thermal indices. Although no direct correlation between cortisol and wool phenotypes was indicated, indirect effects of cortisol presence on wool phenotypes were evident. The climate data did link the climate in Tasmania Midlands to ENSO cycles of Australia between 2010 and 2021. These links explain wool phenotype quality that the statistical analysis did not.