IGF-I gene polymorphism, but not its blood concentration, is associated with milk fat and protein in Holstein dairy cows

E. Bonakdar, H.R. Rahmani, M.A. Edriss and B.E. Sayed Tabatabaei
Published August 31, 2010
Genet. Mol. Res. 9 (3): 1726-1734 (2010)
DOI 10.4238/vol9-3gmr874

About the Authors
E. Bonakdar, H.R. Rahmani, M.A. Edriss and B.E. Sayed Tabatabaei

Corresponding author:
H.R. Rahmani
E-mail: hrahmani@cc.iut.ac.ir


We estimated the allele and genotype frequencies of IGF-I/SnaBI gene polymorphism and the concentration of this protein in Holstein dairy cows. We also examined the association with milk yield (305-day milk yield) and milk components (fat and protein percentage, and 305-day milk protein and fat yield). Blood IGF-I levels were measured and genotyping was performed on 250 Holstein cows of four different herds. In the association studies, traits of interest were analyzed using the GLM procedure of SAS; means of the IGF-I level among genotypes were compared by the LSMeans test. The AB and AA genotypes were the most (0.583-0.661) and least (0.083-0.192) frequent in the herds, respectively; the frequency of the BB genotype ranged from 0.201 to 0.333. The frequency of the A allele ranged from 0.375 to 0.495, while the frequency of the B allele ranged from 0.504 to 0.625, being the dominant allele. The mean level of IGF-I was 107 ± 22 ng/mL for all groups, without any significant correlation with the production traits. Association of IGF-I/SnaBI genotypes with percentage of fat and protein in the milk was relatively high (P < 0.1 and P < 0.05, respectively); the AB genotype was superior to AA and BB genotypes. We concluded that this marker should be considered for milk component selection in Holstein dairy cattle.

Key words: Dairy Holstein; Gene polymorphism; Milk protein; Milk fat; IGF-I.

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