Currently in Uruguay, several experiments of crossbreeding and synthetic breeds are being developed with the inclusion of East Friesian (EF), Finnsheep (F) and Texel (T) meat breeds. The milk production and udder morphology of 57 ewes (8 F, 24 EF and 25 T breeds) from three flocks were evaluated. A total of 161 records (24 F, 68 EF and 69 T breeds) were collected in three test-day controls with average days in milk (DIM) 21, 40 and 60. The ewes were randomly assigned to four experimental groups and separated from the lambs during 4 hours in a good pasture. Before that, it was allowed the nursing of the lambs and the ewes were manual milked to empty their udders. Glandular cistern area (CA) were recorded by ultrasonography (from the side area of the udder) after intramuscular injection of 1 I.U. of synthetic oxytocin, followed by mechanic milking to record the milk weight (MW) and quality (protein-P% and fat-F% percentages). All the traits were adjusted for the effects age of the ewe (1-3), type of lambing (1-2), breed (F, EF, T) and DIM and the square of DIM (both as covariables). Correlation between the residuals of CA and MW from these models were computed. EF showed a wider CA (35.7±2.0 cm2) than F (25.0±3.4) and T (28.4±2.6 cm2) breeds. This was expected because EF is a dairy breed selected to be tolerant to long milking intervals. However, no differences (P>0.05) were observed for milk production (F 382±47; EF 430±29; T 392±37 ml). The F and T breeds showed higher (P0.05) F% (7.0±0.4; 6.9±0.3 and 6.5±0.2, respectively). The correlation between CA and MW residuals were 0.48 F, 0.42 T and zero (P>0.05) for EF breeds. These findings would indicate a greater proportion of alveolar production in the EF breed and/or a better response to the release of milk by the oxytocin injection than the non-dairy breeds. Though, further research would help to determine the breed?s differences between milk production and quality, as their conversion into kilograms of lambs weaned.