title: Single nucleotide polymorphisms in the growth hormone and insulin-like growth factor-1 genes are associated with milk production, body condition score and fertility traits in dairy cows.
abstract: The somatotrophic axis (GH-IGF) is a key regulator of  animal growth and development, affecting performance traits that include milk  production, growth rate, body composition, and fertility. The aim of this study  was to quantify the association of previously identified SNPs in bovine growth  hormone (GH1) and insulin-like growth factor 1 (IGF-1) genes with  direct performance trait measurements of lactation and fertility in  Holstein-Friesian lactating dairy cows. Sixteen SNPs in both IGF-1 and GH1 were genotyped across 610 cows and association analyses were carried out  with traits of economic importance including calving interval, pregnancy rate to  first service and 305-day milk production, using animal linear mixed models  accounting for additive genetic effects. Two IGF-1 SNPs, IGF1i1 and IGF1i2, were significantly associated with body condition score at  calving, while a single IGF-1 SNP, IGF1i3, was significantly  associated with milk production, including milk yield (means ± SEM; 751.3 ±  262.0 kg), fat yield (21.3 ± 10.2 kg) and protein yield (16.5 ± 8.0 kg) per  lactation. Only one GH1 SNP, GH33, was significantly associated  with milk protein yield in the second lactation (allele substitution effect of  9.8 ± 5.0 kg). Several GH1 SNPs were significantly associated with  fertility, including GH32, GH35 and GH38 with calving to  third parity (22.4 ± 11.3 days) (GH32 and GH38 only), pregnancy  rate to first service (0.1%) and overall pregnancy rate (0.05%). The results of  this study demonstrate the effects of variants of the somatotrophic axis on  milk production and fertility traits in commercial dairy cattle.
authors.affiliation: Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Athenry, Co. Galway, Ireland. michael.mullen@teagasc.ie
authors.forename: M P
authors.initials: MP
authors.lastname: Mullen
authors.forename: C O
authors.initials: CO
authors.lastname: Lynch
authors.forename: S M
authors.initials: SM
authors.lastname: Waters
authors.forename: D J
authors.initials: DJ
authors.lastname: Howard
authors.forename: P
authors.initials: P
authors.lastname: O'Boyle
authors.forename: D A
authors.initials: DA
authors.lastname: Kenny
authors.forename: F
authors.initials: F
authors.lastname: Buckley
authors.forename: B
authors.initials: B
authors.lastname: Horan
authors.forename: M G
authors.initials: MG
authors.lastname: Diskin
mesh_terms: D000818:Animals; D001823:Body Composition / Q000235:genetics*; D002417:Cattle / Q000235:genetics* / Q000502:physiology; D005260:Female; D005298:Fertility / Q000235:genetics*; D005838:Genotype; D013006:Growth Hormone / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007774:Lactation / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D011401:Promoter Regions, Genetic
chemical_list: C073294:growth hormone, bovine; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone