Estimation of Individual Heterosis for Lamb Growth in Ghezal and Mehraban Sheep

Data on 361 lambs of Mehraban (n=90), Ghezel (n=92), Ghezel × Mehraban (n=87), and Mehraban × Ghezel (n=92, sire breed listed first) were used to estimate individual Heterosis for lamb growth. The obtained results demonstrated that lambs of purebreds of Ghezel and Mehraban showed the highest and the lowest birth weight, respectively (P < 0.05). Crossbred lambs of Mehraban × Ghezel showed significantly higher (P < 0.05) average birth weight per ewe than Ghezel × Mehraban. Purebred Mehraban lambs showed the lowest total and average six month old weight per ewe (P < 0.05) but the average and total six month old weight per ewe of Ghezel was not different than crossbreds groups of Ghezel × Mehraban and Mehraban × Ghezel lambs (P?0.05). Individual heterosis for the average birth weight, total birth weight, average six month old weight and total six month old weight was estimated to be -0.37, -0.30, 0.22 and -1.03%, respectively (P?0.05).