Ag-reml Estimation of Genetic Parameters for Total Milk Yield in Sicilo-sarde Sheep

Genetic parameters were estimated for total milk yield of a Sicilo-Sarde flock (INRAT (Tunisian National Institute of Agronomic Research) Experiment Station, Béja) for 881 lactations. Total milk yields were calculated from 8220 bimonthly test day records using the Fleischmann method. Animals included in the relationship matrix were 363 ewes and 83 rams. Estimates were from the use of univariate, analytical gradients, restricted maximum likelihood procedures (VCE package). Least squares analyses showed significant effects of year-season, age of ewe, and lambing type on milk yield, with the year-season being the most important factor. Genetic estimates agreed closely with those obtained previously in this population and were lower than those obtained in other dairy sheep populations. Heritability and proportion of permanent environmental variance were 0.14 ± 0.06 and 0.19 ± 0.06 respectively. Genetic and phenotypic variation coefficients reached 7.6% and 23.4% respectively. Our results indicated that efforts should focus on improving the level of management and starting an adequate selection programme, in order to improve milk yield and to repair decreases in milk production level observed in the actual conditions of SiciloSarde breed.