The data of monthly recording on 1464 ewes of the Bulgarian dairy synthetic population (BDSP) with 1648 lactations, reared in 8 farms for 2 year period were compared the measured 120 days milk yield for the milking only period with an interval of 30 days (mlk120) and the predicted one based on 2 test days (P120). The milk yield varied for mlk120 from 13.9 to 222.8 L, and for P120 from 44.5 to 228.7 L. Each trait was analysed with repeatability mixed model. The following genetic parameters were found: genetic variances, respectively 90.5 and 88.8 L2, phenotypic variances 563.1 and 489.4 L2, heritabilities 0.16 and 0.18, repeatability coefficients 0.41 and 0.34. The breeding value (EBV) was used as a selection criterion. When P120 EBV was breeding criterion, with 30% of the potential dams of the next replacement generation of lambs, the wrong ranking was 13.2% compared to mlk120 and with 50% of potential dams the wrong ranking was 7.2%. Possible reasons for the wrong ranking of the ewes were analysed. The predicted milk yield P120 could be used for selection in the flocks for their own replacement. Potential ram-dams could also be selected in the same way, but they have to be reared and contolled in farms with monthly milk recording.
Genetic estimates at monthly and short-cut control of the sheep milk production