ENVIRONMENTAL AND GENETIC EFFECTS ON PRODUCTION TRAITS OF EWES ORIGINALLY FROM DISTINCT ENVIRONMENTS

Wool production and reproductive performance components of similar genotypes, brought from distinct production areas, were evaluated during five years trial at similar environments, such as, joining season and stocking rate on winter improved pasture. The least squares means revealed that the origin (breed) effect concentrated upon the Corriedale ewes wool production, whereas in Romney females it affected the reproductive performance. In the abscence of interaction between origin (breed) and year for most variables, it was assumed that the farm management procedures and/or selection criteria applied on hoggets were determinant of the subsequent lifetime production within each genotype examined. Expecting a better reproductive performance in Romneys, mainly rate of lambs born, weaned and lambs weaning weight, comments were made on the selection criteria employed on this breed over many years. The work has demonstrated that "property of origin (breed)" of sheep composing any experiment aiming at breed comparisons, should be considered as a potential factor capable of biasing information on productive aspects.