DNA Sequence and Haplotype Variation Analyses of Circadian Clock Genes and Their Effects on Phenotypes in the Turkey, Meleagris gallopavo

Present study was planned to compare the phenotypic variation of performances traits among commercial (CC) and heritage varieties of turkeys. Information about heritage turkey varieties continues to be limited. In addition, the emerging turkey genome sequence provides a unique opportunity to understand the DNA sequence variation and its associations with performance traits. The turClock, turPer3, turCry1 and turCry2 genes were screened and evaluated for its association with their performance traits. As expected, CC turkeys were superior to heritage birds in performance for most of the traits evaluated. However, heritage turkeys showed better reproductive performances compared to CC turkeys. A total of 41 SNPs were identified from the genes that screened. The haplogroups in the turClock gene were significantly associated with body weight (BW) at 309 d of age, feed conversion ratio (FCR) for 34 - 68 d and 69 - 159 d, egg production and average egg weight (P " 0.05). The haplogroups developed from turPeriod-3 gene were significantly associated with BW at 231 d of age, average daily gain (ADG) for 160 - 231 d, FCR for 69 - 159 d and 160 - 231 d, egg production traits, semen quality traits and plasma melatonin concentration (P " 0.05). In the turCry1 gene, haplogroups were significantly associated with ADG for 35 - 68 d, FCR for 160 - 231 d and 34 - 231 d, egg production and ejaculate volume (P " 0.05). The haplogroups identified from turCry2 gene were significantly associated with BW at 34, 68 and 231 d of age, ADG for 160 - 231 d, FCR for 34 - 68 d, average egg weight (P " 0.05). These findings reveal that phenotypic variation observed in growth and reproductive parameters among turkeys could be used for selecting birds for future breeding programs. DNA sequence variations at the nucleotide and haplotype levels are associated with some of growth, reproductive parameters and plasma melatonin of turkeys. Thus DNA sequence variations that identified of the circadian genes may have some regulatory role in the molecular mechanism of the circadian clock which may affect the circadian rhythm of the animal.