Genetic trend for milk and fat productions for Holstein cattle in Minas Gerais State

Revista Brasileira de Zootecnia

Durães, Marcus Cordeiro²  Teixeira, Nilson Milagres²  Valente, José²  Barra, Ricardo Bertola¹  Freitas, Ary Ferreira de² 

[1] Associação de Criadores de Gado Holandês de Minas Gerais;Embrapa Gado de Leite, Juiz de Fora

关键词: animal model;    genetic parameters;    maximum likelihood   IntroduçãoDesde a década de 50;    em várias partes do mundo;    vêm sendo divulgadas estimativas de ganhos genéticos anuais ou tendências genéticas;    empregando-se diferentes metodologias de estimação;   

DOI  :  10.1590/S1516-35982001000100011

学科分类：兽医学

来源: Universidade Federal de Vicosa

【 摘 要 】

- The objective of this work was to estimate the genetic trends for milk and fat yields of Holstein Dairy Cattle, in Minas Gerais State, Brazil. The statistical analyses were made by means of mixed models, using restricted maximum likelihood and animal model. The fixed effects studied were: herd-year-season at calving and linear and quadratic effect of age at calving besides the animal and residual random effects. The genetic trends were obtained by regression of the breeding value on the year of birth of cows. Records used in the analyses were 18,482 first lactations of cows born from 1986 to 1996. The genetic trends for milk and fat yield were 18.4 and 0.6 kg, respectively. The average of milk and fat yields were 5083 ± 50 to 6876 ± 51 kg, and from 172.6 ± 1.7 to 228.5 ± 1.7 kg, respectively. The breeding values estimated were negative in 1986 and 1987, and positive thereafter, with accentuate increase in the last years. This is an indication that milk farmers of Minas Gerais State have been taking strategies in order to increase the milk productions.

【 授权许可】

CC BY-NC