LAUSR

Simple Summary Molecular genetic approaches have been developed over the last half-century to identify genetic variation associated with economically important growth performance and carcass characteristics. In the livestock sector, identifying and localizing the genes responsible for each trait, as well as selecting beneficial alleles based on live animal experiments, meat production, and nutritional quality, have played an essential role in improving productivity. The purpose of this study is to examine the association between IGF1 5′UTR polymorphisms and various growth and carcass parameters of meat-type sheep breeds raised in Turkey. A total of eight nucleotide changes were identified that were able to characterize three IGF1 5′UTR variants, and certain variants were associated with variations in chest width and leg circumference. The P1 variants had a leaner profile and the P2 variants had a higher percentage of rack and loin. Nucleotide sequence variations in IGF1 5′UTR could, thus, be exploited for marker-assisted selection in order to enhance growth and production attributes and carcass quality. Abstract This investigation was conducted to determine how the growth and carcass traits of meat-type sheep breeds raised in Turkey are associated with IGF1 5′UTR polymorphisms. Overall, 202 lambs from five breeds were evaluated. We identified eight nucleotide changes (seven substitutions and one deletion) in three variants of IGF1 5′UTR by SSCP analysis and nucleotide sequencing. It was found that the P1 variants had a unique deletion (g.171328230 delT), while the P2 variants were identified by SNPs rs401028781, rs422604851, and g.171328404C > Y. The P3 variants possessed one heterozygous substitution (g.171328260G > R) and three homozygous substitutions (g.171328246T > A, g.171328257T > G, g.171328265T > C) not observed in P1 or P2. Based on the growth and production traits, a statistically significant difference was found only in chest width at weaning (p < 0.01) and leg circumferences at yearling (p < 0.05). The P1 variants showed a leaner profile with a higher Musculus longissimus dorsi, but the differences were not significant (p > 0.05). The P2 variants had a higher percentage of rack (p < 0.01) and loin (p > 0.05). Moreover, there was no discernible difference between variants, even though the P3 variants had a higher percentage of neck and leg and the P1 variants had a higher percentage of the shoulder. It is concluded that nucleotide changes in IGF1 5′UTR could be exploited utilizing a marker-assisted selection technique to increase growth and production attributes, as well as carcass quality traits.