Interplay between stress and reproduction: Novel epigenetic markers in response to shearing patterns in Australian Merino sheep (Ovis aries)

Abstract

In this study, we determined the effect(s) of shearing on Australian Merino ewes (Ovis aries). To test this research question, we used a suite of field and laboratory methods including GPS collars, wool cortisol and novel epigenetic markers identified using Illumina NovaSeq RRBS. Single shorn ewes (n =24) kept on their full fleece throughout the entire gestation period while twice shorn ewes (n =24) had their wool shorn early in gestation. We have discovered one locus (Chr20:50404014) which was significantly associated with different shearing treatments (twice or single shorn ewes), (FDR = 0.005). This locus is upstream of a protein coding gene (ENSOARG00000002778.1), which shows similarities to the forkhead box C1 (FOXC1) mRNA using BLAST searches. We discovered that 36 gene loci were significantly modulated either between different shearing treatments or late vs early pregnancy ewes. Similarly, in lambs we identified 16 annotated gene loci that were significant between late vs early pregnancy. Early shorn ewes grazed 10% higher and maintained stronger body condition. Wool cortisol levels were significantly lower in the early shorn ewes during mid- and late gestation. Lambs bred from twice shorn ewes had on average better visual wool quality parameters in terms of micron, spin finesses and curvature. Collectively, this research provides a new dataset combining physiological, molecular epigenetics and digital tracking indices that advances our understanding of how Merino ewes respond to shearing frequency and this information could guide further research on sheep breeding and welfare. Significance StatementThis study provides novel data on the molecular epigenetic signatures in Merino sheep under exposure to natural environmental and management factors. We have discovered DNA methylation profiles from ewes and lambs that are directly associated with whole- animal physiology, development and growth. The baseline data can provide a useful resource for future research in many key areas such as animal welfare, diseases and climatic resilience that will benefit sheep and wool production.