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Vega-Murillo V.E.,Research Center Regional Golfo Centro | Rios-Utrera A.,Campo Experimental la Posta | Montano-Bermudez M.,CENID Fisiologia y Mejoramiento Animal | Martinez-Velazquez G.,Sitio Experimental El Verdineno
Tropical and Subtropical Agroecosystems | Year: 2012

Covariance components and genetic parameters were estimated in Simmental, Simbrah and Simmental x Zebu calves fitting six alternative models to birth weight (BW; n=105,297), 205-day weight (WW; n=82,752) and 365-day weight data (YW; n=49,450) provided by Asociación Mexicana de Criadores de Ganado Simmental Simbrah, A.C. Models ranged from a model which included direct additive genetic effects (Model 1) to a model which included direct and maternal additive genetic effects, their covariance and maternal permanent environmental effects (Model 6). Fixed effects were: contemporary group, age of dam, proportion of Simmental genes, heterozygosity and recombination losses. Estimates of direct and maternal heritability varied between alternative models. Due to the problems associated with the estimation of the direct-maternal correlation, which was extremely high (absolute value), Model 4, which included both dams' genetic and permanent environmental effects in addition to direct additive genetic effects, was considered to be the most appropriate for all traits. Application of any of the other models would result in inaccurate expected progeny differences, affecting selection efficiency. Model-4 estimates of direct heritability, maternal heritability and of the ratio of maternal permanent environmental variance to the total phenotypic variance were: 0.17, 0.01 and 0.03; 0.14, 0.02 and 0.04; and 0.15, 0.01 and 0.01 for BW, WW and YW, respectively. Source


Rios-Utrera A.,Campo Experimental la Posta | Vega-Murillo V.E.,Campo Experimental la Posta | Martinez-Velazquez G.,Sitio Experimental El Verdineno | Montano-Bermudez M.,CENID Fisiologia y Mejoramiento Animal
Tropical and Subtropical Agroecosystems | Year: 2011

Six models to estimate genetic parameters for birth weight (BW), weaning weight adjusted to 205 days (W205), and yearling weight adjusted to 365 days (W365) were compared. Model A included direct genetic effects. Model AP allowed for direct genetic and permanent environmental effect of the dam. Model AM included direct genetic and maternal genetic effects. Models AMC and AMP were the same as Model AM but they also allowed for the covariance between direct and maternal genetic effects, and the common environmental effect due to the dam, respectively; and Model AMCP was fitted for all three random effects plus the covariance between direct and maternal effects. Models were compared using the likelihood ratio text. The AMC model was selected to be the most appropriate for BW and W205, whereas Model A was chosen for W365. When maternal effects were included, direct genetic variance and direct heritability estimates were reduced for BW and W205. Direct heritability estimates with appropriate models were: 0.13, 0.21 and 0.20 for BW, W205 and W365. Heritability of maternal effects with appropriate models was: 0.15 and 0.32 for BW and W205, and direct-maternal genetic correlations with appropriate models were: -0.67 and -0.69 for BW and W205, respectively. Source


Utrera A.R.,Instituto Nacional de Investigaciones Nucleares | Velazquez G.M.,Sitio Experimental El Verdineno | Murillo V.E.V.,Instituto Nacional de Investigaciones Nucleares | Bermudez M.M.,CENID Fisiologia y Mejoramiento Animal
Revista Mexicana De Ciencias Pecuarias | Year: 2012

Genetic effects for growth traits of Mexican Charolais and Charbray cattle estimated with alternative models. Data recorded from 1997 to 2009 by the Charolais-Charbray Herd Book of Mexico were analyzed with six different animal models to estimate genetic parameters for birth weight (n=105,599), weaning weight adjusted to 205 d (n=89,111) and yearling weight adjusted to 365 days (n=55,284). Model 1 included direct additive genetic effects of the animal. Model 2 allowed for a common environmental effect due to the dam, fitting it as an additional random effect. Model 3 included the animal's direct genetic effect, and the dam's maternal genetic effect, assuming a covariance equal to zero between them. Model 4 was the same as Model 3 but it also allowed for a common environmental effect due to the dam. Model 5 is identical to Model 3, but included a covariance between direct and maternal genetic effects. Model 6 was fitted for all three random effects plus the covariance between direct and maternal genetic effects. Compared with any of the other models, the most complete model (Model 6) substantially reduced the -2log L (P<0.05), providing the best fit for the three growth traits. Comparison between Model 1 and Model 6 across traits showed that Model 1 yielded smaller estimates of direct genetic variance, in contrast with results from previous studies. However, estimates of the residual variance for Model 1 were significantly greater than estimates for Model 6. Source


Pech C.I.V.M.,Campo Experimental Mococha | Vazquez J.A.T.,CENID Fisiologia y Mejoramiento Animal | Zepeda A.B.,Sitio Experimental El Verdineno | Utrera A.R.,Campo Experimental la Posta | And 4 more authors.
Revista Mexicana De Ciencias Pecuarias | Year: 2012

Genetic parameters for growth traits of Katahdin lambs were estimated using six variants of the animal model. Data on birth weight (BW; n= 13,099), weaning weight adjusted to 75 d (WW; n=11,509) and postweaning weight adjusted to 120 d (AW; n=6,886) were collected for seven years (2004-2010) in 20 states across Mexico. Analyses were carried out by ignoring or including maternal effects. The simplest model included the direct additive genetic effect as the only random effect. The most complete model included direct and maternal genetic effects, their covariance, and the maternal permanent environmental effect. Selection of the best model was based on likelihood-ratio test. When maternal effects were not taken into account, estimates of direct heritability and direct genetic variance were overestimated for all traits. Direct heritability estimates for the best model were 0.18 ± 0.03, 0.30 ± 0.04, and 0.20 ± 0.05 for BW, WW and AW, respectively. Maternal heritability estimates also varied depending on the model; estimates ranged from 0.05 to 0.23, 0.00 to 0.12, and 0.09 to 0.25 for BW, WW and AW. Ignoring maternal effects in the model would result in inaccurate genetic evaluation for growth traits in Katahdin sheep. Source

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