Evolución de la producción y características de calidad de lana de primer vellón de animales Merino Australiano en un esquema de mejora genética por resistencia a parasitosis gastrointestinales

One of the main limitations in the sheep industry in Uruguay are gastrointestinal parasitosis. The two species most involved are Haemonchus contortus and Trichostrongylus colubriformis. However, to alleviate this problem there are various strategies. This work was carried out at the Estación Experimental Facultad de Agronomía Salto (EEFAS), in which a selection program for resistance to gastrointestinal parasitosis is carried out, in which national and foreign genetics are introduced. The objective was to analyze how the selection for the trait of resistance to gastrointestinal parasitosis affects the production of wool in quantity and quality, specifically the father effect on the production of lambs. Data from first shearing of a total of 717 Australian Merino lambs born in EEFAS from 2015 to 2020 were used. Analysis was done on dirty fleece weight (PVS), clean fleece weight (PVL), diameter (DIAM), body weight (PC), staple length (LM) and egg count per gram of feces (HPG). The phenotypic, genetic, and environmental trend for PVS and PVL increased, for DIAM there were no significant variations. The behavior for LM was similar to PC and their trends were upward. For HPG, a slight drop in the phenotypic effect was observed, while it presented a more accentuated negative genetic effect. All the variables increased and decreased in the years of study, mainly due to genetics, since the environment had little influence. By adding genetics directed to a trait (resistance) and selecting animals solely for that trait, the other variables are indirectly modified. The study determined that by adding genetics directed to a trait, it can be improved and then stabilize the other variables through a selection that is not only directed to the trait of interest, but also considers the other traits of productive interest.