Genetic improvement of wool production in Spanish Merino sheep: genetic parameters and simulation of selection strategies

Wool production of the Spanish Merino breed was analysed after several decades of genetic selection to improve meat production. Genetic parameters (heritability and correlations) were estimated for greasy fleece weight, staple length, crimp frequency and fibre diameter of 1869 Spanish Merino purebred sheep. Heritabilities ranged from 0.08 +/- 0.050 (fibre diameter) to 0.22 +/- 0.060 (staple length), and the genetic correlations ranged from -0.63 +/- 0.159 (crimp frequency - staple length) to 0.75 +/- 0.222 (fibre diameter - staple length). Genetic simulations were developed to show the consequences of eight selection strategies, which included single trait selection on wool traits and liveweight (the current selection criteria) and index selection combining traits. The results show that it is possible to improve wool and growth traits at the same time. Also, our results show there is indirect genetic progress for wool characteristics using the current liveweight selection criterion.