Association of GH/<i>HaeIII</i> polymorphism with growth and developmental traits of Morkaraman sheep

Abstract. This study investigated the impact of GH gene polymorphism in Morkaraman ewes on placental traits and lamb development characteristics across three years (2020–2022) at Atatürk University Sheep Farm, Erzurum. PCR–RFLP method with HaeIII endonuclease was used to identify GH gene polymorphism. Two genotypes were found in Morkaraman sheep: AA (50.40 %) and AB (49.60 %). Ewes with AA and AB genotypes showed birth weights of 4.32 and 4.43 kg, weaning weights of 14.32 and 15.42 kg, and daily gains of 209 and 223 g, respectively. While GH genotype did not significantly affect birth weight, it significantly influenced weaning weight (p&lt;0.01) and daily live weight gain (p&lt;0.05). Placental characteristics examined included placental weight, surface area, efficiency, total cotyledon numbers, cotyledon length and width, cotyledon efficiency, total cotyledon weight, and density. Genotype showed no significant effect on placental traits, but parity significantly affected placental area (p&lt;0.05). While lamb sex had no impact, delivery type significantly influenced placental weight (p&lt;0.05). Genotype showed highly significant effects (p&lt;0.01) on total cotyledon area, weight, and density among cotyledon characteristics. The present study found that Morkaraman ewes with the AB genotype of the GH gene revealed superior growth and placental characteristics, with their lambs also exhibiting enhanced growth traits. The results of the study indicate that beneficial genotypes can be identified from birth, thus leading to the development of improved breeding strategies.