Genetic Parameters for Milk Yield and Lactation Persistency Using Random Regression Models in Girolando Cattle.
A total of 32,817 test-day milk yield (TDMY) records of the first lactation of 4,056 Girolando cows daughters of 276 sires, collected from 118 herds between 2000 and 2011 were utilized to estimate the genetic parameters for TDMY via random regression models (RRM) using Legendre's polynomial functions whose orders varied from 3 to 5. In addition, nine measures of persistency in milk yield (PSi) and the genetic trend of 305-day milk yield (305MY) were evaluated. The fit quality criteria used indicated RRM employing the Legendre's polynomial of orders 3 and 5 for fitting the genetic additive and permanent environment effects, respectively, as the best model. The heritability and genetic correlation for TDMY throughout the lactation, obtained with the best model, varied from 0.18 to 0.23 and from -0.03 to 1.00, respectively. The heritability and genetic correlation for persistency and 305MY varied from 0.10 to 0.33 and from -0.98 to 1.00, respectively. The use of PS7 would be the most suitable option for the evaluation of Girolando cattle. The estimated breeding values for 305MY of sires and cows showed significant and positive genetic trends. Thus, the use of selection indices would be indicated in the genetic evaluation of Girolando cattle for both traits.
Facultad de Ciencias Agrarias, Universidad Nacional del Altiplano, Puno 21001, Perú .
Ali William
AW
Canaza-Cayo
Animal Science Departament, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil .
Paulo Sávio
PS
Lopes
Embrapa Gado de Leite, Eugênio do Nascimento Street, 610, Juiz de Fora, MG 36038-330, Brazil .
Marcos Vinicius Gualberto Barbosa
MV
da Silva
Animal Science Departament, Universidade Federal de Viçosa, Viçosa, MG 36570-000, Brazil .
Robledo
R
de Almeida Torres
Embrapa Gado de Leite, Eugênio do Nascimento Street, 610, Juiz de Fora, MG 36038-330, Brazil .
Marta Fonseca
MF
Martins
Embrapa Gado de Leite, Eugênio do Nascimento Street, 610, Juiz de Fora, MG 36038-330, Brazil .
Wagner Antonio
WA
Arbex
Facultad de Ciencias Agrarias, Universidad Nacional del Altiplano, Puno 21001, Perú .
Jaime Araujo
JA
Cobuci
Cattle; Genetic Parameters; Genetic Trend; Lactation Persistency; Legendre’s Polynomials; Random Regression Model