Genetic Parameters For Weaning Weight Research Articles

Estimation of direct and maternal genetic parameters for weaning weight in Hungarian Simmental cattle

The aim of the current research was to estimate variance components and genetic parameters of weaning weight in Hungarian Simmental cattle. Weaning weight records were obtained from the Association of Hungarian Simmental Breeders. The dataset comprised of 44,278 animals born from 1975 to 2020. The data was analyzed using the restricted maximum likelihood methodology of the Wombat software. We fitted a total of six models to the weaning weight data of Hungarian Simmental cattle. Models ranged from a simple model with animals as the only random effect to a model that had maternal environmental effects as additional random effects as well as direct maternal genetic covariance. Fixed effects in the model comprised of herd, birth year, calving order and sex. Likelihood ratio test was used to determine the best fit model for the data. Results indicated that allowing for direct-maternal genetic covariance increases the direct and maternal effect dramatically. The best fit model had direct and maternal genetic effects as the only random effect with non-zero direct-maternal genetic correlation. Direct heritability, maternal heritability and direct maternal correlation of the best fit model was 0.57, 0.16 and -0.78 respectively. The result indicates that problem of (co-)sampling variation occurs when attempting to partition additive genetic variance into direct and maternal components.

Genetic evaluation of weaning weight and udder score in Nellore cattle

The aim of this study was to estimate genetic parameters for weaning weight (WW) and udder score (US) of 186,151 Nellore animals raised in extensive systems. The (co)variance components and estimated breeding values (EBVs) were obtained by two-trait analyses using Bayesian inference. The maternal effect (ME) was expressed as the maternal additive genetic variance of the calf's weaning weight (WW). The direct heritabilities were 0.13 ± 0.012 and 0.23 ± 0.012 for WW and US, respectively. The maternal heritability was 0.11 ± 0.012 for WW. The genetic correlations between WW and US (0.48 ± 0.053), WW and ME (0.41 ± 0.067), and US and ME (0.31 ± 0.041) were positive and moderate. Cows with maternal udder scores (US_M) 3 and 4 showed higher EBVs for ME (2.58 ± 0.070 and 2.88 ± 0.214, respectively) and their progeny had higher EBVs for WW (4.58 ± 0.058 and 5.07 ± 0.168) and US (0.20 ± 0.001 and 0.26 ± 0.005). The genetic trends demonstrate genetic progress in the selection program over the years, with values of 0.19 kg and 0.01 points for WW and US, respectively. The genetic trend in ME was 0.04 kg for WW. In addition, a positive genetic correlation was observed between these traits, as well between the traits and ME, i.e., selection would result in positive genetic gains. The use of US_M may help improve body weight and udder quality in the progeny. Furthermore, the trends indicate that the selection adopted on the farms has been effective in promoting genetic progress.

Estimation of genetic parameters for weaning weight of Awassi lambs by using classical and Bayesian methods

The aim of this study was to estimate variance components and genetic parameters with six different animal models and two approaches (Bayesian and classical) on weaning weight (WW) of Awassi lambs. For this purpose, the data were obtained from Sheep and Goat Breeders' Associations of Osmaniye in Turkey. The data of 4971 progenies (from 80 rams and 1917 ewes) born between 2012 and 2016 raised under traditional conditions were evaluated. Year/season, sex, birth type, dam age, and flock size were fixed effects. All these effects except birth type were found statistically significant (P < 0.01). The overall least squares mean of weaning weight (WW) was obtained as 17.93 ± 0.05 kg. Variance components and genetic parameters were estimated by MCMC algorithms with R (for Bayesian approach) and by REML procedure with MTDFREML (for classical approach) programs. The Akaike information criterion (AIC), the log likelihood function (-2logL), and deviance information criterion (DIC) values were taken as criteria to choose the best model. Direct heritabilities of WW ranged from 0.20 to 0.35 across the models. The genetic correlation between additive genetic effect and maternal effect ranged from 0.00 to 1.00. The results were found similar across methodologies and maternal additive genetic variance resulted in lower than direct additive genetic variance. According to this study, both approaches are suitable for estimation of genetic parameters in the case of low sample size. However, the Bayesian approach, becoming increasingly popular, may be feasible to estimate variancecovariance components and genetic parameters.

Estimation of Genetic Parameters for Wool Traits in Angora Rabbit

Different genetic parameters for weaning weight and wool traits were estimated using restricted maximum likelihood (REML) in Angora rabbits. Total wool yield of first (I), second (II) and third (III) clips were taken as a separate trait under study. The records from more than 2,700 animals were analysed through fitting six animal models with various combinations of direct and maternal effects. A log likelihood ratio test was used to select the most appropriate model for each trait. Direct heritability estimates for the wool traits were found to be moderate to high across different models. Heritability estimates obtained from the best model were 0.24, 0.22, 0.20 and 0.21 for weaning weight, clip I, II and III; respectively. Maternal effects especially due to permanent environment had higher importance at clip I and found to be declining in subsequent clips. The estimates of repeatability of doe effect on wool traits were 0.44, 0.26 and 0.18 for clip I, II and III; respectively. Weaning weight had moderately high genetic correlations with clip I (0.57) and II (0.45), but very low (0.11) with clip III. Results indicated that genetic improvement for wool yield in Angora rabbit is possible through direct selection. Further, weaning weight could be considered as desirable trait for earliest indirect selection for wool yield in view of its high genetic correlation with wool traits.

Effect of pre-weaning selection on estimates of genetic parameters and breeding values for post-weaning growth rate of beef bulls on test

Data on South African Angus cattle consisting of 45 259 records on weaning weight (WWT), 4 360 records on average daily gain from on-farm test (ADG-D) and 1 118 from centralized test (ADG-C) were analyzed to evaluate the effect of pre-weaning selection on estimates of genetic parameters and subsequent estimated breeding values (EBV) for post-weaning average daily gain. (Co)variance components and genetic parameters for weaning weight (WWT), ADG-C and ADG-D were estimated by REML procedures fitting three different animal models. Model 1 was a univariate model of WWT, ADG-C or ADG-D and did not account for the effect of pre-weaning selection on post-weaning ADG. Model 2 was a two-trait model of WWT and either ADG-C or ADG-D. Model 3 was a multi-trait animal model including WWT, ADG-C and ADG-D. Estimates of heritability for ADG-C were 0.39 +/- 0.080, 0.42 +/- 0.060 and 0.44 +/- 0.010 from Model 1, 2 and 3 respectively. Corresponding estimates for ADG-D were 0.18 +/- 0.020, 0.19 +/- 0.020 and 0.21 +/- 0.020 respectively. Rank correlations based on EBVs for ADG-C for all bulls were 0.92, 0.83 and 0.94 for Model 1 vs. Model 2, Model 1 vs. Model 3, and Model 2 vs. Model 3, respectively and they indicated a possible re-ranking of bulls when including or excluding a correlated pre-weaning trait. Rank correlations for ADG-D also followed a similar trend. Inclusion of pre-weaning information in genetic analysis for post-weaning average daily gain is necessary to account for selection at weaning.

Associações genéticas entre pesos e características reprodutivas em rebanhos da raça Nelore

Dados de 14.918 animais da raça Nelore nascidos entre 1991 e 2000, provenientes de rebanhos localizados nas regiões Sul e Sudeste do País, foram utilizados para estimar componentes de co-variância, herdabilidade e correlações genéticas de peso ao desmame (PD), peso a 1 ano de idade (PA), peso ao sobreano (PS), peso ao primeiro parto (PPP), idade ao primeiro parto (IPP) e dias para o primeiro parto (DP). As estimativas dos componentes de co-variância e dos parâmetros genéticos foram obtidas pelo método de máxima verossimilhança restrita, em análises multivariadas. As herdabilidades estimadas para PD, PA, PS, PPP, IPP e DP foram de 0,26; 0,30; 0,34; 0,35; 0,14 e 0,07, respectivamente. Correlações genéticas negativas foram estimadas entre pesos medidos em diferentes idades e IPP, as quais variaram de -0,31 a -0,16. Do mesmo modo, as estimativas de correlação genética entre PD × DP (-0,09); PA × DP (-0,13); PS × DP (-0,17) e PPP × DP (-0,16) foram negativas, embora de menor magnitude. As correlações genéticas estimadas entre as características de crescimento e a IPP foram favoráveis. Assim, a seleção para aumento de peso deve promover redução da IPP. A alta correlação genética estimada entre IPP e DP (0,73) indica que o uso de DP na seleção de bovinos de corte pode promover resposta correlacionada favorável na idade ao primeiro parto.

Selection of a suitable data set and model for the estimation of genetic parameters of the weaning weight in beef cattle

Abstract. The objective of this paper was to select a suitable data subset and statistical model for the estimation of genetic parameters for weaning weight of beef cattle in the Czech Republic. Nine subsets were tested for the selection of a suitable subset. The subsets differed from each other in the limit of sampling criteria. The most suitable subset satisfied these conditions: at least 5 individuals per each sire, 5 individuals per HYS (herd, year, season), 2 sires per HYS, and individuals per dams that have at least one half-sister and two offspring (n = 4 806). The selection of a suitable model was carried out from 10 models. These models comprised some of the random effects: direct genetic effect, maternal genetic effect, permanent maternal environment effect, HYS, sire × herd or sire × year interaction, and some of the fixed effects: dam’s age, sex (young bull, heifer × single, twin born), HYS, year, herd. The direct heritability (h2a) ranged from 0.06 to 0.17, of maternal heritability (h2m) from 0.03 to 0.06. The genetic correlations between the direct and maternal effect (ram) were in the range of –0.15 –0.42.

Aspectos genéticos do peso à desmama e de algumas características reprodutivas de fêmeas Nelore

Estimaram-se os parâmetros genéticos do peso à desmama ajustado para 240 dias de idade (PD240), da idade ao primeiro parto (IPP), da idade ao segundo parto (ISP) e do primeiro intervalo de partos (PIEP) em animais da raça Nelore, pelo método da máxima verossimilhança restrita, utilizando-se o aplicativo MTDFREML, sob modelo animal. As estimativas de herdabilidade incluindo somente uma variável foram: 0,48±0,20; 0,27 ±0,15; 0,14±0,16; e 0,03±0,13, respectivamente, para PD240,, IPP, ISP e PIEP. As correlações genéticas estimadas entre IPP e ISP e PIEP foram de 0,97 e -0,92, respectivamente. A correlação genética entre ISP e PIEP foi de -0,82. As correlações genéticas entre PD240 e IPP, ISP e PIEP foram -0,20, 0,00 e 1,00, respectivamente.

Variance and covariance components for weaning weight for Herefords in three countries.

Records from the Hereford Associations of the United States (USA), Canada, and Uruguay were used to estimate genetic and phenotypic variances and covariances for weaning weight. Estimation was done using a complete animal model, relatively large data sets, and the same methodology for the three countries in order to determine whether genetic parameters for weaning weight were homogeneous across environments. Data were composed of 2,322,722, 487,661, and 102,986 edited weaning weight records for USA, Canada, and Uruguay, respectively. Ten samples were obtained from each country by eliminating data from small herds with fewer than 500 records, selecting herds at random from the entire data set after removing the small herds, and then retaining the direct-sire-connected contemporary groups within each sample. The final sample sizes ranged from 9,832 to 46,377 records. An accelerated EM-REML algorithm was used in estimating the (co)variance components in each sample. The estimates were pooled by calculating the arithmetic mean of the 10 samples from within each country. Direct and maternal (in parentheses) heritability estimates were .24 (.16), .20 (.16), and .23 (.18) for USA, Canada, and Uruguay, respectively. Maternal heritabilities reported here are nearly 50% smaller than the values currently used in national genetic evaluation for the breed, which were estimated using sire-maternal grandsire models. Covariance between direct and maternal was negative in all countries, accounting for 6, 8, and 10% of the total phenotypic variation, and the total dam effect was 32.5, 37.0, and 34.0% in USA, Canada, and Uruguay, respectively. Total heritabilities were similar among the countries, with values of .19, .19, and .17 for the three respective countries. The similarity of genetic and environmental parameters across the three countries suggests that joint genetic evaluation is feasible across environments provided that the genotype x environment interaction is negligible and can be ignored.

Comparison of models to estimate maternal effects for weaning weight of Swiss Angus cattle fitting a sire×herd interaction as an additional random effect

Field data of Swiss Angus cattle were used to explore the consequences of including in the model additional random effects, such as maternal effects and a sire×herd interaction (SH), on the estimates of genetic parameters for weaning weight. Data were analysed using Restricted Maximum Likelihood (REML), applied to animal models comprising fixed effects of herd, year of birth, month of birth, sex, birth type, age of dam and age of calf at weaning. All investigated models included a random direct genetic effect, but differed for combinations of random maternal genetic and permanent environmental effects as well as for direct-maternal genetic covariance and for sire×herd interaction. The models including SH effect fitted the data significantly better (P<0.01) than those ignoring the interaction. Ignoring SH effect resulted in a strong negative correlation between additive direct and maternal effects. The models including SH resulted in reduced estimates of direct and maternal genetic variance and of direct-maternal genetic covariance and, consequently, in a less negative correlation between direct and maternal genetic effects. With the inclusion of SH effect in the model, the direct-maternal covariance was no longer statistically significant. The SH variance represented only 7% of the phenotypic variance but accounted for a great amount of the covariance between direct and maternal genetic effects estimated ignoring SH.

Estimates of genetic parameters for weaning weight of beef cattle accounting for direct-maternal environmental covariances

Restricted Maximum Likelihood algorithm estimates of (co)variance components due to maternal effects as well as a regression on maternal phenotype were obtained for seven weaning weight data sets of Australian and New Zealand beef cattle. Fitting such regression, analyses accounted for environmental covariances between dams and their offspring. Results show a substantial, negative regression on maternal phenotype (up to −0.2) for Hereford field data, accompanied by small, negative estimates of a direct-maternal genetic covariance. In contrast, for Angus and Limousins, the direct-maternal genetic covariance was clearly more important than its environmental counterpart, i.e., for these breeds an estimate of the direct-maternal genetic correlation of about −0.5 could not be attributed to a negative environmental relationship which previously had not been modeled correctly. Fitting a sire × herd-year interaction as an additional random effect increased the likelihood dramatically for all data sets. While estimates of the regression on maternal phenotype were little affected, fitting the interaction reduced estimates of the direct-maternal genetic covariance, substantially so for Angus and Limousin, reducing (absolute value) estimates of the corresponding correlations to −0.3 to −0.2.

Estimation of genetic variance and covariance components for weaning weight in Simmental cattle.

The objectives of this study were to estimate genetic parameters for weaning weight of Simmental cattle from data without selective reporting and to examine heterogeneity of parameters with a multiple trait approach. Heterogeneity of (co)variance components (VC) by sex is accounted for in national genetic evaluations for Simmental cattle. Completely reported data were split into bull, heifer, and steer populations to obtain VC estimates. Estimates of direct-maternal genetic correlation were negative, which suggests that selective reporting was not a cause of a negative correlation in Simmental data. However, analyzing only data for males does not account for selection on females and vice versa. Heterogeneous VC for sex were evaluated by analyzing Simmental data using a multiple trait model where male and female data were treated as two traits. Estimates of heritability of direct (maternal) effects were .19 (.07) and .25 (.12) and estimates of the direct-maternal genetic correlation were -.05 and -.20 for males and females, respectively. The multiple trait model fit the data better (P < .01) than the model under the assumption of homogeneous VC.