Avaliação da persistência na lactação da raça Guzerá, utilizando modelos de regressão aleatória

Freitas, L.S.; Silva, M.A.; Verneque, R.S.; Valente, Bruno D.; Corrêa, G.S.S.; Ferreira, R.F.; Peixoto, Maria Gabriela Campolina Diniz; Santos, G.G.

doi:10.1590/s0102-09352010000200021

Cited by 8 publications

(3 citation statements)

References 13 publications

(2 reference statements)

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“…The amplitudes of variation in the heritability estimates of the models ranged from 0.20 to 0.33, with the lowest heritability estimates obtained for TDMY in the eighth month and the highest in the second or third month. Freitas et al (2010), who also evaluated data on the Guzerat breed, found similar results but observed the highest heritability values at the start of lactation. Hereditability estimates similar to those in the present study, obtained using Wilmink and AS functions, were reported by Herrera et al (2008) and Pereira et al (2010), with values varying from 0.15 to 0.33 for TDMY of Gyr cows.…”

Section: Resultssupporting

confidence: 52%

Comparison of random regression models to estimate genetic parameters for milk production in Guzerat (Bos indicus) cows

Santos

Peixoto²,

Aspilcueta-Borquis³

et al. 2013

Genet. Mol. Res.

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ABSTRACT. Random regression models have been widely used to estimate genetic parameters that influence milk production in Bos taurus breeds, and more recently in B. indicus breeds. With the aim of finding appropriate random regression model to analyze milk yield, different parametric functions were compared, applied to 20,524 test-day milk yield records of 2816 first-lactation Guzerat (B. indicus) cows in Brazilian herds. The records were analyzed by random regression models whose random effects were additive genetic, permanent environmental and residual, and whose fixed effects were contemporary group, the covariable cow age at calving (linear and quadratic effects), and the herd lactation curve. The additive genetic and permanent environmental effects were modeled by the Wilmink function, a modified Wilmink function (with the second term divided by 100), a function that combined third-order Legendre polynomials with the last term of the Wilmink function, and the Ali and Schaeffer function. The residual variances were modeled by means of 1, 4, 6, or 10 heterogeneous classes, with the exception of the last term of the Wilmink function, for which there were 1, 3, 6, or 10 classes. The models gave similar hereditability estimates, ranging from 0.20 to 0.33. Genetic correlations between adjacent records were high values (0.83-0.99), but they declined when the interval between the test-day records increased, and were negative between the first and last records. The model employing the Ali and Schaeffer function with six residual variance classes was the most suitable for fitting the data.

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Section: Resultssupporting

confidence: 52%

Comparison of random regression models to estimate genetic parameters for milk production in Guzerat (Bos indicus) cows

Santos

Peixoto²,

Aspilcueta-Borquis³

et al. 2013

Genet. Mol. Res.

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“…Referring to the Zebu breeds, some studies have been conducted referring to estimates of genetic parameters and comparisons among lactation, repeatability, or random regression models with the Gyr breed Herrera et al, 2008;Ledic et al, 2002). Freitas et al (2010) estimated genetic parameters for TDMY and persistency of lactation measurements for a Guzerat population in Brazil, using random regression models. Nevertheless, studies are still scarce for the Guzerat breed.…”

Section: Introductionmentioning

confidence: 99%

Genetic parameters for test-day milk yield, 305-day milk yield, and lactation length in Guzerat cows

et al. 2013

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a b s t r a c tMilk production in tropical environments requires the use of crossbreeding systems including breeds well adapted to harsh conditions, but with lower productivities when compared to specialized breeds. Besides the genetic improvement for milk production, lactation lengths also need to be studied for most of these breeds. Accordingly, genetic parameters were estimated for 305-day cumulative milk yield (MY305), test-day milk yield (TDMY), and lactation length (LL) using information from the first lactations of 2816 Guzerat cows selected for milk production in 28 herds in Brazil. Contemporary groups were defined as herd, year and season of the test for TDMY, and as herd, year and season of calving for MY305 and LL. Variance components were estimated with the restricted maximum likelihood method under a multi-trait animal model. Heritabilities estimated for TDMY ranged from 0.16 to 0.24, and were 0.24 and 0.12 for MY305 and LL, respectively. Genetic correlations were high and positive, ranging from 0.51 to 0.99 among TDMY records, from 0.81 to 0.98 between each TDMY and MY305, and from 0.71 to 0.94 between each TDMY and LL. Genetic parameters obtained in this study indicated the possibility of using test-day records for the prediction of breeding values for milk yield in this population of the Guzerat breed. The use of TDMY as selection criteria would result in indirect gains in MY305 and LL. However, the highest response to selection for MY305 would be obtained by direct selection for this trait.

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“…These characteristics have a significant correlation with the others for being associated to components that explain a small proportion of linear trait variability in cattle, The reason for proposing the discard is that variables highly correlated to the major components of higher variance (eigenvalues lower than 0.7) represent practically insignificant variation, and therefore they do not contribute to selection. However, heritability estimates and genetic correlations must be taken into account, as the characteristics for discarding may have higher heritability than those with which they correlate favorably (FREITAS et al, 2010). This fact may cause the selection to be only based on the selected characteristics (meaning those present in the first ten main components) may lead to lower genetic gains.…”

Section: Resultsmentioning

confidence: 99%

Phenotypic evaluation of trait types in Guzerá cows of different calving orders

Júnior

Rangel

Lima

et al. 2017

SCA

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The objective of this study was to evaluate the effect of parity on linear trait types in Guzerá cows using multivariate techniques. Data were collected from 68 purebred Guzera females, young (1 st and 2 nd calving order) and adults (3 rd to 7 th calving order). Measurements were collected using a tape measure, a hypometer, a 40 cm graduated ruler and a 180° protractor. PRCOMP procedure of the R program was used for analyzing the main components. The variables related to rump (height, angularity, ileum and ischium length and width), body (length), udder (height of posterior ligament) and milk production were more important to explain the phenotypic variation in Guzerá cattle. Young Guzerá cows had lower body length, narrower rumps, better udder ligaments and lower milk yield than adult cows. Key words: Dairy cattle. Multivariate. Zebu cattle. ResumoObjetivou-se avaliar a efeito da ordem de parto, por meio de técnicas multivariadas, sobre as características lineares de tipo de vacas da raça Guzerá. Foram utilizados dados de 68 fêmeas da raça Guzerá, puras de origem, jovens (1ª e 2ª ordem de parto) e adultas (3ª a 7ª ordem de parto). As medidas foram coletadas com auxílio de fita métrica, hipômetro, régua graduada de 40 cm e transferidor de ângulos 180°. Para as análises de componentes principais utilizou-se o procedimento PRCOMP do programa R. As variáveis relacionadas à garupa (altura, angulosidade, comprimento e largura de íleo e ísquios), corpo (comprimento), úbere (altura do ligamento posterior) e produção de leite apresentaram maior importância para explicar a variação fenotípica de bovinos Guzerá. Vacas jovens da raça Guzerá apresentaram menor comprimento corporal, garupas mais estreitas, melhores ligamentos de úbere e menor produção de leite que as vacas adultas. Palavras-chave: Bovinocultura leiteira. Multivariada. Zebuínos.

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Avaliação da persistência na lactação da raça Guzerá, utilizando modelos de regressão aleatória

Cited by 8 publications

References 13 publications

Comparison of random regression models to estimate genetic parameters for milk production in Guzerat (Bos indicus) cows

Comparison of random regression models to estimate genetic parameters for milk production in Guzerat (Bos indicus) cows

Genetic parameters for test-day milk yield, 305-day milk yield, and lactation length in Guzerat cows

Phenotypic evaluation of trait types in Guzerá cows of different calving orders

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