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The present project aimed to improve the number and total weight of lambs at birth, three months, and six months of age, as well as to enhance the daily weight gain rate during different growth periods of Moghani lambs through the implementation of community-based breeding programs. The initial core of this project comprised 13 flocks, 650 ewes, and 52 superior rams. Complete details of the animals and their pedigrees were recorded in designated forms. The recorded traits included body weight at various ages and the daily weight gain rate in the pre-weaning (birth to three months), post-weaning (three to six months), and overall growth (birth to six months) periods, and ewe reproductive traits including twinning rate and the number of lambs born per ewe per lambing. The SAS 9.1 software was used for statistical analysis of the collected data and evaluation of the effect of environmental factors on the studied traits. To estimate genetic parameters, including heritability and genetic and phenotypic correlations of traits, single-trait and two-trait animal models were used in the Wombat software. The effect of fixed environmental factors including year of birth, lamb sex, birth type, dam age, and flock were considered as effective factors. Based on the results, the heritability of birth weight, three-month weight, and six-month weight were estimated to be 0.020, 0.044, and 0.070, respectively. Also, the heritability for daily weight gain in the pre-weaning, post-weaning, and overall growth periods was estimated to be 0.029, 0.015, and 0.065, respectively. Correlation analysis showed that there are positive and significant genetic and phenotypic correlations between most body weight and daily weight gain traits at different ages. The range of phenotypic correlations between different traits varied from -0.171 (between ADG0-3 and ADG3-6 traits) to +0.990 (between ADG0-6 and WG6 traits), and the range of genetic correlations varied from 0.049 (between ADG0-3 and ADG3-6 traits) to 0.992 (between ADG0-6 and WG6 traits). The results of this research showed that training and encouraging livestock breeders to establish improved nucleus flocks and exchange genes is a practical and effective strategy to improve the genetic progress of important economic traits in rural and nomadic livestock breeders' flocks.
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