Transient Treatment of Pregnant Merino Ewes with Modulators of Cortisol Biosynthesis Coinciding with Primary Wool Follicle Initiation Alters Lifetime Wool Growth

The study investigated the impact of transient manipulation of maternal cortisol levels on the wool characteristics of Merino sheep. Pregnant ewes were treated with either metyrapone (a cortisol inhibitor) or betamethasone (a cortisol analogue) during a critical period of fetal wool follicle development (Days 55-65 post-conception). Lambs exposed to metyrapone in utero exhibited hairier birthcoats, a 10% increase in staple length, and reduced crimp frequency for the first three shearings compared to control and betamethasone groups (P < 0.05). Gene expression analysis indicated up-regulation of genes involved in hair and skin development. The findings suggested that altering maternal cortisol levels during key developmental windows could have long-term effects on wool production traits in Merino sheep.