title: Effect of lactation length adjustment procedures on genetic parameter estimates for buffalo milk yield.
abstract: The objectives of this study were to estimate the genetic parameters for milk yield unadjusted and adjusted for days in milk and, subsequently, to assess the influence of adjusting for days in milk on sire rank. Complete lactations from 90 or 150 days of lactation to 270 or 350 days in milk were considered in these analyses. Milk yield was adjusted for days in milk by multiplicative correction factors, or by including lactation length as a covariable in the model. Milk yields adjusted by different procedures were considered as different traits. Heritability estimates varied from 0.17 to 0.28. Genetic correlation estimates between milk yields unadjusted and adjusted for days in milk were greater than 0.82. Adjusting for days in milk affected the parameter estimates. Multiplicative correction factors produced the highest heritability estimates. More reliable breeding value estimates can be expected by including short length lactation records in the analyses and adjusting the milk yields for days in milk, regardless of the method used for the adjustment. High selection intensity coupled to the inclusion of short length lactations and adjustment with multiplicative factors can change the sire rank..
authors.affiliation: Departamento de Zootecnia, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista "Julio de Mesquita Filho", Jaboticabal, SP, Brazil.
authors.forename: Fernando
authors.initials: F
authors.lastname: Baldi
authors.forename: Monyka Marianna Massolini
authors.initials: MM
authors.lastname: Laureano
authors.forename: Daniel Gustavo Mansan
authors.initials: DG
authors.lastname: Gordo
authors.forename: Annaiza Braga
authors.initials: AB
authors.lastname: Bignardi
authors.forename: Rusbel Raul Aspilcueta
authors.initials: RR
authors.lastname: Borquis
authors.forename: Lucia Galvão
authors.initials: LG
authors.lastname: de Albuquerque
authors.forename: Humberto
authors.initials: H
authors.lastname: Tonhati