THE PRKAG3 GENE POLYMORPHISMS AND THEIR ASSOCITATIONS WITH GROWTH PERFORMANCE AND BODY INDICES IN BARKI LAMBS

ABSTRACT
In this study the polymorphisms rof a variable fragment located between exon 4 and exon 6 of the ovine protein kinase adenosine mono-phosphate activated gamma 3 (PRKAG3) gene were detected in 59 males and 62 females of Barki lambs using the polymerase chain reaction-single strand conformational polymorphism (PCR-SSCP) analysis, followed by cloning and sequencing the detected SSCP banding patterns.
The associations of PRKAG3 gene polymorphisms with growth traits (birth weight, weaning weight, pre-weaning daily gain, marketing weight and post-weaning daily gain) and body indices (body mass index, skeletal muscle index, body index and relative body index) were tested using general linear models of SAS (2000). The models included animal genotype, gender of lamb and parity of ewe as fixed effects. Age at weaning was included as a covariate in the models assessing the effect of PRKAG3 genotype on pre-weaning daily gain and weaning weight as well as age at marketing was included in the models assessing the effect of PRKAG3 genotype on post-weaning daily gain, marketing weight and body indices.
Three genotypes (AA, AB and BB) were identified with frequencies of 0.26, 0.50 and 0.24, respectively. These genotypes were derived from two alleles (A and B) with frequencies of 0.51 and 0.49, respectively. The variation in PRKAG3 gene showed significant associations with marketing weight (P ˂ 0.05), post-weaning daily gain (P ˂ 0.01), skeletal muscle index (P ˂ 0.05) and body mass index (P ˂ 0.01). The presence of B allele was associated with heavier marketing weight (P ˂ 0.05), faster post-weaning daily gain (P ˂ 0.01) and higher body mass index (P ˂ 0.01) and skeletal muscle index (P ˂ 0.05).
The presented results give valuable information to select for B allele and against A allele of PRKAG3 gene to improve marketing weight and muscularity of Barki lambs.