title: A new way to measure milk yield persistency: a genetic point of view with application to Gyr (Bos indicus) cattle.
abstract: The objective of this work was to estimate genetic parameters for a measure of persistency of milk yield and to evaluate its association with 305-d cumulative milk yield and lactation length. 12 346 records from 8202 dairy Gyr cows including lactations up to fifth calving were used. The measure of persistency was obtained from one of the parameters of a quadratic model that describes the cumulative yield across lactation as a function of days in milk. A three-trait multivariate analysis was done. Heritability and repeatability for persistency were 0.08 and 0.21, respectively. Deviance Information Criterion provided evidence that the additive genetic covariance between the measure of persistency studied and 305-d cumulative yield is zero. Genetic correlations between persistency and lactation length were 0.50 and 0.27 for first or all lactations, respectively. Milk yield persistency as measured in this study has low heritability. Selection for persistency can increase lactation length. The measure of milk yield persistency studied here is genetically independent of total milk yield and can be included in routine genetic evaluations of dairy cattle.
authors.affiliation: Departamento de Zootecnia,Faculdade de Ciências Agrárias e Veterinárias,Universidade Estadual Paulista,Rodovia Carlos Tonnani,Km 5,CEP 14870 -000 Jaboticabal,SP,Brazil.
authors.forename: Rodrigo Junqueira
authors.initials: RJ
authors.lastname: Pereira
authors.affiliation: Departamento de Zootecnia,Faculdade de Ciências Agrárias e Veterinárias,Universidade Estadual Paulista,Rodovia Carlos Tonnani,Km 5,CEP 14870 -000 Jaboticabal,SP,Brazil.
authors.forename: Denise Rocha
authors.initials: DR
authors.lastname: Ayres
authors.affiliation: Instituto de Zootecnia,Rodovia Carlos Tonanni,Km 94,CEP 14160-900,Sertãozinho,SP,Brazil.
authors.forename: Lenira
authors.initials: L
authors.lastname: El Faro
authors.affiliation: Instituto de Zootecnia,Rodovia Carlos Tonanni,Km 94,CEP 14160-900,Sertãozinho,SP,Brazil.
authors.forename: Aníbal Eugênio
authors.initials: AE
authors.lastname: Vercesi Filho
authors.affiliation: Embrapa Gado de Leite,Rua Eugênio do Nascimento,610,Bairro Dom Bosco,CEP 36038-330,Juiz de Fora,MG,Brazil.
authors.forename: Rui da Silva
authors.initials: Rda S
authors.lastname: Verneque
authors.affiliation: Departamento de Zootecnia,Faculdade de Ciências Agrárias e Veterinárias,Universidade Estadual Paulista,Rodovia Carlos Tonnani,Km 5,CEP 14870 -000 Jaboticabal,SP,Brazil.
authors.forename: Lucia Galvão
authors.initials: LG
authors.lastname: de Albuquerque
mesh_terms: D000818:Animals; D002417:Cattle / Q000235:genetics* / Q000502:physiology*; D005260:Female; D007774:Lactation / Q000235:genetics / Q000502:physiology*; D008892:Milk; D008954:Models, Biological; D013997:Time Factors
keywords: Bayesian inference; dairy cattle; genetic parameters; persistency