<b>Differential </b><b>T</b><b>ranscriptomics and </b><b>M</b><b>etabolomics Analyses of the </b><b>S</b><b>kin of </b><b>C</b><b>oarse and </b><b>F</b><b>ine Liaoning Cashmere Goats</b>

Secondary follicles (SFs) in cashmere goats determine cashmere yield and quality and are regulated by a variety of genes, signaling pathways, and metabolic pathways. The aim of this study was to identify these regulatory factors and elucidate the SF growth mechanism as well as develop strategies to improve cashmere quality and yield. In this study, we categorized four hundred 18-month-old female Liaoning cashmere goats into coarse and fine hair types according to Chinese Cashmere Classification Standard GB18267-2013 (with 16.0–18.5 μm diameters classified as coarse and 14.5–16.0 μm as fine). Subsequently, the diameters and lengths of the cashmere fibers were measured. We then selected six goats with traits similar to those in each of the two groups for further analyses. Fiber diameters between the groups were significantly different (P&lt;0.05), but average lengths were not (P&gt;0.05). Metabolomics analysis revealed 211 differentially expressed genes between the groups, including FGF18, KRT36, KRT79, and AWAT2, which were enriched in the PPAR and glycerol-lipid metabolism signaling pathways that regulate the growth and development of hair follicles and sebum secretion. Fifty differentially expressed metabolites were detected in the skin, including melatonin, which regulates cellular ion channels and participates in neurological channels by enriching ABC transporter protein pathways, amino acid biosynthesis and metabolism, and arachidonic acid metabolism. Ion channels are involved in the neuroendocrine and immune systems of the body and indirectly regulate hair growth and development.