Título:	Adjustment of lactation curves of Holstein cows from herds of Minas Gerais, Brazil.
Autoria:	AZEVEDO JUNIOR, J. GONÇALVES, T. de M. SOUZA, J. C. de RODRIGUEZ, M. A. P. COSTA, C. N. CARVALHEIRA, J. G. V.
Afiliação:	Jairo Azevedo Junior, UFLA; Tarcisio de Moraes Gonçalves, UFLA; José Camisão de Souza, UFLA; Mary Ana Petersen Rodriguez, Universidade Estadual de Montes Claros; CLAUDIO NAPOLIS COSTA, CNPGL; Julio Gil Vale Carvalheira, Universidade do Porto, Portugal.
Ano de publicação:	2018
Referência:	Journal of Agricultural Science, v. 10, n. 2, 2018.
Páginas:	14 p.
Conteúdo:	Abstract Random regression models (RRM) differ in terms of the functions used to describe the shape of lactation curves. The aim was to compare random regression models under different functions to describe the lactation curves from Holstein cows in herds of the state of Minas Gerais. A database of 28,118 production records was analyzed using the test-day records of 4,230 first parity cows from five herds. The Wilmink, Ali & Schaeffer and Legendre polynomial (orders 4, 5 and 6) functions were adjusted in RRM to model the mean production trend (fixed) and genetic and permanent environmental (random) effects. The residual variances were assumed to be constant throughout lactation. Analyses were performed using the AIREMLF90 program. Except for the model with the polynomial function of order 5, all models converged. The Wilmink function showed lower values for criteria based on the -2log (L), AIC and BIC. The model with the Legendre polynomial of order 6 showed lower residual variance. Heritability estimates were similar between functions, ranging from 0.07 to 0.18 and were higher from 215 days of lactation. From 155 days of lactation, genetic and permanent environmental correlations between successive controls are of high magnitude. The Wilmink function is the most suitable for the study of milk yields from primiparous Holstein cows. The selection of animals is possible from 155 days of lactation on. Permanent environmental effects have greater influence on the milk production at the end of lactation of primiparous cows and should be considered since they are important and may be cumulative throughout lactation.
NAL Thesaurus:	Dairy cattle Heritability
Palavras-chave:	Models comparison Permanent environmental effects Random regression model
Digital Object Identifier:	10.5539/jas.v10n2p1
Tipo do material:	Artigo de periódico
Acesso:	openAccess
Aparece nas coleções:	Artigo em periódico indexado (CNPGL)