title: Genetic analysis of fat-to-protein ratio, milk yield and somatic cell score of Holstein cows in Japan in the first three lactations by using a random regression model.
abstract: We estimated the genetic parameters of fat-to-protein ratio (FPR) and the genetic correlations between FPR and milk yield or somatic cell score in the first three lactations in dairy cows. Data included 3,079,517 test-day records of 201,138 Holstein cows in Japan from 2006 to 2011. Genetic parameters were estimated with a multiple-trait random regression model in which the records within and between parities were treated as separate traits. The phenotypic values of FPR increased soon after parturition and peaked at 10 to 20 days in milk, then decreased slowly in mid- and late lactation. Heritability estimates for FPR yielded moderate values. Genetic correlations of FPR among parities were low in early lactation. Genetic correlations between FPR and milk yield were positive and low in early lactation, but only in the first lactation. Genetic correlations between FPR and somatic cell score were positive in early lactation and decreased to become negative in mid- to late lactation. By using these results for genetic evaluation it should be possible to improve energy balance in dairy cows.
authors.affiliation: Animal Breeding and Reproduction Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Nishiura
authors.affiliation: Animal Breeding and Reproduction Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Sasaki
authors.affiliation: Livestock Improvement Association of Japan, Tokyo, Japan.
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Aihara
authors.affiliation: Animal Breeding and Reproduction Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Japan.
authors.forename: Hisato
authors.initials: H
authors.lastname: Takeda
authors.affiliation: Animal Breeding and Reproduction Research Division, NARO Institute of Livestock and Grassland Science, Tsukuba, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Satoh
mesh_terms: D000818:Animals; D002417:Cattle / Q000378:metabolism* / Q000502:physiology*; D004734:Energy Metabolism; D005223:Fats / Q000032:analysis*; D005260:Female; D007564:Japan; D007774:Lactation / Q000235:genetics* / Q000378:metabolism*; D008892:Milk / Q000166:cytology / Q000378:metabolism*; D008894:Milk Proteins / Q000032:analysis*; D015233:Models, Statistical; D036801:Parturition; D012044:Regression Analysis; D013997:Time Factors
chemical_list: D005223:Fats; D008894:Milk Proteins
keywords: dairy cow; fat-to-protein ratio (FPR); genetic parameter; random regression model