M. Bagheri - Department of Genomics and Genetic Engineering, Razi Vaccine and Serum Research Institute (RVSRI), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Islamic Republic of Iran.
M. Moradi-Shahrbabak - Department of Animal Science, University of Tehran, Karaj, Islamic Republic of Iran.
R. Vaez-Torshizi - Department of Animal Science, Tarbiat Mordares University, Tehran, Islamic Republic of Iran.
A. Zahmatkesh - Department of Genomics and Genetic Engineering, Razi Vaccine and Serum Research Institute (RVSRI), Agricultural Research, Education and Extension Organization (AREEO), Karaj, Islamic Republic of Iran.

In this study, ۱۹۷۳-۲۰۰۳ data of ۱۲,۳۲۸ animals from Abbasabad Baluchi Sheep Breeding Station, Iran, were used to estimate genetic and phenotypic correlations between Total Weight of lambs Weaned per Ewe Joined in the first, ۲nd, ۳rd and ۴th lambing (TWW۱/EJ, TWW۲/EJ, TWW۳/EJ, and TWW۴/EJ, respectively), and TWW of the total four lambing (TWWt/EJ). Also, the study aimed to estimate correlations of TWW۱/EJ...TWW۴/EJ and Birth Weight (BW) as well as Weaning Weight (WW). The (co)variance components and genetic correlations were estimated by DFREML procedures. Genetic correlation between TWW۱/EJ and TWWt/EJ was high and positive (۰.۷۶). Genetic correlations of TWW/EJ in different lambing with BW and WW ranged from ۰.۱۶ to ۰.۳۲ and ۰.۹۵ to ۰.۹۷, respectively. Repeatability of TWW/EJ for lambing ۱-۴ was ۰.۱۵. Results suggested that selection for increased lifetime reproductive performance could be based on TWW۱/EJ in the first lambing. Overall, results indicate that TWW/EJ, as an important but sex-limited trait, may be used in selection criterion to indirectly improve the related traits.

Birth weight, Composite traits, Heritability, Weaning weight.