title: Genetic associations between milk fat-to-protein ratio, milk production and fertility in the first two lactations of Thai Holsteins dairy cattle.
abstract: The aims of this study were to estimate, simultaneously, the genetic parameters of test-day milk fat-to-protein ratio (FPR), test-day milk yield (MY), and days-open (DO) in the first two lactations of Thai Holsteins. A total of 76 194 test-day production records collected from 8874 cows with 8674 DO records between 2001 and 2011 from different lactations were treated as separated traits. The estimates of heritability for test-day FPR in the first lactation showed an increasing trend, whereas the estimates in the second lactation showed a U-shape trend. Genetic correlations for FPR-DO and MY-DO showed a decreasing trend along days in milk (DIM) in both lactations, whereas genetic correlations for FPR-MY increased along DIM in the first lactation but decreased in the second lactation. Genetic correlations of FPR between consecutive DIM were moderate to high, which showed the effectiveness of simultaneous analyses. Selection of FPR in the early stage has no adverse effect on MY and DO for the first lactation but has a negative effect on MY and positive effect on DO for the second lactation. This study showed that genetic improvement of the energy balance using FPR, MY and DO with multi-trait test day model could be applied in a Thailand dairy cattle breeding program.
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand.
authors.forename: Somsook
authors.initials: S
authors.lastname: Puangdee
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand.
authors.forename: Monchai
authors.initials: M
authors.lastname: Duangjinda
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand.
authors.forename: Wuttigrai
authors.initials: W
authors.lastname: Boonkum
authors.affiliation: Department of Animal Science, Faculty of Agriculture, Khon Kaen University, Thailand.
authors.forename: Suporn
authors.initials: S
authors.lastname: Katawatin
authors.affiliation: Department of Livestock Development, Bureau of Biotechnology in Livestock Production, Thailand.
authors.forename: Sayan
authors.initials: S
authors.lastname: Buaban
authors.affiliation: Faculty of Agricultural Technology, Songkhla Rajabhat University, Songkhla, Thailand.
authors.forename: Mongkol
authors.initials: M
authors.lastname: Thepparat
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics*; D004734:Energy Metabolism; D005223:Fats / Q000032:analysis*; D005260:Female; D005298:Fertility / Q000235:genetics*; D056726:Genetic Association Studies; D007774:Lactation / Q000235:genetics*; D008892:Milk / Q000737:chemistry*; D008894:Milk Proteins / Q000032:analysis*; D013785:Thailand
chemical_list: D005223:Fats; D008894:Milk Proteins
keywords: FPR; Thai Holsteins; days open; genetic parameters; negative energy balance