Phenotypic Responses to Selection for Ultrafine Wool in Uruguayan Yearling Lambs

This study evaluated the phenotypic trends for wool and growth traits of fine Merino genetic nucleus in Uruguay. Data were collected from one-year-old lambs over a twenty-year period (1999–2018). The overall aim selection flock was to reduce fiber diameter with concomitant increases fleece live weights. Traits analyzed included (FD), greasy weight (GFW), coefficient variation FD (CVfd), staple length (SL), scoured yield (SY), post-shearing (LW), eye muscle area (EMA) fat thickness (FAT). approximately 5300 male female analyzed. During period, decreased by 3 µm, whereas GFW LW increased at least 0.5 3.0 kg, respectively. There interactions between sex individual year all traits. Except FAT, other affected dam age. indicates that program applied resulted reductions LW. Therefore, results indicate it is possible produce ultrafine semi-extensive grazing systems without compromising economically relevant lambs.