title: IGF-I gene polymorphism, but not its blood concentration, is associated with milk fat and protein in Holstein dairy cows.
abstract: 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.
authors.affiliation: Department of Animal Science, College of Agriculture, Isfahan University of Technology, Isfahan, Iran.
authors.forename: E
authors.initials: E
authors.lastname: Bonakdar
authors.forename: H R
authors.initials: HR
authors.lastname: Rahmani
authors.forename: M A
authors.initials: MA
authors.lastname: Edriss
authors.forename: B E
authors.initials: BE
authors.lastname: Sayed Tabatabaei
mesh_terms: D000818:Animals; D002417:Cattle; D005223:Fats / Q000378:metabolism*; D005260:Female; D005838:Genotype; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism*; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D008894:Milk Proteins / Q000378:metabolism*; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D005223:Fats; D008894:Milk Proteins; D007334:Insulin-Like Growth Factor I