Effect of the &amp;lt;i&amp;gt;IGF-I&amp;lt;/i&amp;gt; gene polymorphism on growth, body size, carcass and meat quality traits in Coloured Polish Merino sheep

Sławomir Mroczkowski,Bronisław Borys,Ewa Grochowska,Piotr Janiszewski,Jan Knapik

doi:10.5194/aab-60-161-2017

Abstract

Abstract. Insulin-like growth factor I, encoded by the IGF-I gene, plays a role in cell growth and differentiation, embryogenesis, metabolism regulation, skeletal growth, and protein synthesis. The aims of this study were to investigate the polymorphism in the 5′ flanking region of the IGF-I gene and evaluate associations between the single-nucleotide polymorphism (SNP) in this gene and growth, body size, carcass and meat quality traits in Coloured Polish Merino sheep. In total 78 live and post mortem traits were investigated. Polymorphism in the IGF-I gene was identified with the use of the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) method in 305 Coloured Polish Merino sheep. In association studies, traits of interest were analysed with the use of the MIXED and GENMOD procedures of the SAS statistical package. Two alleles named A and B, and two IGF-I genotypes – AA and AB – were detected. The A allele and the AA genotype were predominant, with the frequencies of 91.6 and 83.3 %, respectively. The IGF-I genotype was found to have a highly significant effect on fore shank weight (P = 0.006), kidney fat class (P = 0.002) and EUROP fat class (P = 0.005). Furthermore, the IGF-I genotype significantly affected external fatness of carcass class (P = 0.038), drip loss (P = 0.049), and subjective assessment of meat colour (P = 0.043), and it tended to be associated with longissimus dorsi (LD) muscle width (P = 0.063) and flavour (0.067). Concluding, the IGF-I gene could be considered as a candidate gene of selected carcass and meat quality traits in sheep.

Highlights

Insulin-like growth factor I (IGF-I) is a polypeptide hormone that is encoded by the IGF-I gene and is similar in molecular structure to insulin
IGF-I participates in the somatotrophic axis together with growth-hormone-releasing hormone (GHRH), growth hormone (GH), insulin-like growth factor II (IGF-II), and their associated binding proteins (BPs) and receptors (GHRHR, GHR, insulin-like growth factor I receptors (IGF-IR) and IGF-IIR)
None of the analyses showed any significant effect of the IGF-I genotype on the abovementioned characteristics; the IGF-I gene polymorphism tended to be associated with longissimus dorsi (LD) muscle width (P = 0.063)

Summary

Introduction

Insulin-like growth factor I (IGF-I) is a polypeptide hormone that is encoded by the IGF-I gene and is similar in molecular structure to insulin. IGF-I is believed to mediate a wide spectrum of biological responses such as cell growth and differentiation, embryogenesis, metabolism regulation, skeletal growth, and protein synthesis (Baxter, 1986; Clemmons et al, 1987; Froesch et al, 1985). For these reasons, the IGF-I gene is considered as a functional candidate for a number of production traits, i.e. growth, carcass and meat quality traits in livestock. Lamb body weight is one of the factors that regulate incomes from meat

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