Defining breeding goal and strategy for Dalagh Sheep.

In this study, (Co)variance components and genetic parameters for production and reproduction traits in Dalagh sheep were estimated using multivariate animal model analysis with DFREML procedure on collected records during period of 1988 to 2009 in Dalagh breeding station in Gorgan. 4 flocks with 1155 head of breeding ewe during annual cycle of production in extensive production system were used to determine breeding objectives and relative economic values. Stochastic simulation was used to produce base population size of 100 to 300 from a large population with multivariate normal distribution. The direct heritability of birth weight(BW), weaning weight(WW) and 6- month weight(6MW) based on the most appropriate model were assessed to be 0.22, 0.37 and 0.28, respectively. Heritability for average daily gain from birth to weaning(ADG0-3) and average daily gain from weaning to 6- month weight(ADG3-6), and Kleiber ratio from birth to weaning(KR0-3) and kleiber ratio from weaning to 6 month (KR3-6) were estimated to be 0.26, 0.13, 0.18 and 0.23, respectively. heritability of number and weight of born lambs' traits was estimated 0.000 and 0.009and for number and weight of weaning lambs traits was estimated 0.019 and 0.137. The highest relative economic values gained from maximum profit approach were calculated for six-mounth weight , survival rate of ewe and conception rate and the lowest of them were related to ewe's live weight and replacement weight. The genetic gain and profitability were increased with increasing flock size and decreasing proportion of ram. The rate of inbreeding was increased with reducing proportion of ram. To prevent excessive inbreeding in herd, small herds must be merged. The fourth index was introduced as the most appropriate selection index for Dalagh sheep by comparision of different indexes and Duncan test. The fourth index was only contained total lamb weight weaned per ewe exposed. Key Words: Genetic parameters, Economic weight, Breeding objective, Selection index, Dalagh sheep