Genetic variation in the growth hormone (GH) gene influences postnatal growth and placental structure in indigenous...

This study investigated the association between growth hormone (GH) gene polymorphism and postnatal growth and placental traits of Tuj sheep over a 3-year period (2020-2022) at the Atatürk University Sheep Research Farm, Erzurum. The genotype-phenotype association analyses comprised Tuj ewes and their progeny. The polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method using the Hae-III restriction enzyme was applied to identify GH gene variants. Three genotypes were detected: LL (49.0 %), LV (39.0 %), and VV (11.0 %). The mean birth weights were 4.45 kg (LL), 4.52 kg (LV), and 4.36 kg (VV); the weaning weights were 14.80, 15.55, and 14.43 kg, respectively; and the average daily gains were 0.213, 0.226, and 0.209 $\mathrm{kg}{d}^{-1}$ , respectively. Although the GH genotype had no significant association with birth weight ( $p>0.05$ ), it was significantly associated with weaning weight ( $p<0.05$ ) and daily live weight gain ( $p<0.01$ ). The present study involves an analysis of the placental traits (placental area, placental weight, and placental efficiency). The results indicated that there were no statistically significant relationships between the GH genotype and placental traits ( $p>0.05$ ). The study revealed a significant effect of parity on placental area ( $p<0.05$ ). Twin lambs demonstrated a higher placental weight than single lambs ( $p<0.05$ ). No significant differences were identified between lamb sex and placental traits. The LV genotype in Tuj ewes was found to be associated with slightly higher growth performance and had favorable indicators for placental traits in comparison with the LL and VV genotypes. These findings suggest that GH gene polymorphism could serve as a potential genetic marker for improving growth performance in Tuj sheep populations.