Modeling the effect of the age of dam at calving on the weaning weight of Charolais-Zebu crossbred calves
01 Jul 2009-Revista Brasileira De Zootecnia (Sociedade Brasileira de Zootecnia)-Vol. 38, Iss: 7, pp 1229-1237
TL;DR: O trabalho foi realizado com o objetivo de avaliar alternativas para a modelagem do efeito da idade da vaca ao parto sobre o peso a desmama of bezerros mesticos Charoles-Zebu.
Abstract: The objective of this study was to evaluate alternatives for modeling the age of dam at calving (AOD) effect on the weaning weight of Charolais-Zebu crossbred calves. Data from 56,965 calves were analyzed, using statistical models considering the fixed effects of the contemporary groups, sire and dam genetic groups, and AOD. The AOD effect was fitted to models using annual age classes, and ordinary quadratic to quintic-ordered polynomials (OP) or segmented polynomials (SP) with two, three, four, six and twelve evenly spaced intervals. In the case of segmented polynomials, general linear and quadratic effects and only one quadratic additional term from each knot were considered. The AOD effects were nested within sex of calf in all cases. According to the fitting criteria, the F-test for the reduction of residual sum of squares, coefficient of determination, residual sum of squares and mean of squared residuals, the three interval segmented polynomial (two knots) fitted to the data as well as the more complex polynomials.
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TL;DR: In this paper, the degree of multicollinearity and the variables involved in linear dependence relations in additive-dominant models were assessed based on the variance inflation factor and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables.
Abstract: The objective of this work was to assess the degree of multicollinearity and to identify the variables involved in linear dependence relations in additive-dominant models. Data of birth weight (n=141,567), yearling weight (n=58,124), and scrotal circumference (n=20,371) of Montana Tropical composite cattle were used. Diagnosis of multicollinearity was based on the variance inflation factor (VIF) and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables. The first model studied (RM) included the fixed effect of dam age class at calving and the covariates associated to the direct and maternal additive and non-additive effects. The second model (R) included all the effects of the RM model except the maternal additive effects. Multicollinearity was detected in both models for all traits considered, with VIF values of 1.03 - 70.20 for RM and 1.03 - 60.70 for R. Collinearity increased with the increase of variables in the model and the decrease in the number of observations, and it was classified as weak, with condition index values between 10.00 and 26.77. In general, the variables associated with additive and non-additive effects were involved in multicollinearity, partially due to the natural connection between these covariables as fractions of the biological types in breed composition.
14 citations
Cites background from "Modeling the effect of the age of d..."
...Problems related to multicollinearity in models for estimation of genetic effects in crossbred populations were reported in several studies (Cassady et al., 2002; Roso et al., 2005a; Pimentel et al., 2006; Toral et al., 2009; Lopes et al., 2010)....
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TL;DR: The breed compositions, the individual and maternal heterozygosis, the sex and age of dam at calving were significant sources of residual heteroskedasticity and the a posteriori means for heritabilities and sire and dam classifications were altered due to genetic and residual heterotasticity.
Abstract: The objective of the present study was to analyze models with genetic and/or residual heteroskedasticity for genetic evaluation of the weaning weight of Charolais-Zebu crossbred calves. Weaning weight data from 56,965 crossbred calves were analyzed using animal models with different combinations of genetic and residual heteroskedasticity and/or homoskedasticity. The inference on a posteriori distributions of genetic parameters were by the Monte Carlo method via Markov chains. The model with genetic and residual heteroskedasticity was the best fit on the data. Groups of animals with different genetic compositions, expressed as percentages of Charolais-Zebu breed alleles and individual and maternal heterozygosis, had different genetic variances. These genetic variances could be modeled by linear functions of the Charolais and Zebu genetic variances and the variance attributed to segregation. The breed compositions, the individual and maternal heterozygosis, the sex and age of dam at calving were significant sources of residual heteroskedasticity. The a posteriori means for heritabilities and sire and dam classifications were altered due to genetic and residual heteroskedasticity.
4 citations
TL;DR: Evaluated alternatives for modeling the interaction between age of dam at calving and the dam genetic group (DGG) on the weaning weight (W225) of Charolais-Zebu (Ch-Z) crossbred calves found the CLA model provided the best fit.
Abstract: The objective of this study was to evaluate alternatives for modeling the interaction between age of dam at calving (AOD) and the dam genetic group (DGG) on the weaning weight (W225) of Charolais-Zebu (Ch-Z) crossbred calves. Data from 56,965 crossbred calves were analyzed by the least square method. Regression coefficients for age of dam at calving were estimated nested into each class of the dam genetic group (CLA model); for age of dam at calving × dam Charolais percentage (age of dam at calving × FCh) and age of dam at calving × dam heterozygosity (age of dam at calving × FH) (FChFH model); for age of dam at calving × dam Charolais percentage (FCh model); for age of dam at calving × FH (FH model); or only for age of dam at calving (NINT model). Segmented polynomials were used to model the general shape of the age of dam at calving effect and its interaction with dam genetic group. The knots were at 6.33 and 10.66 years of age of dam at calving and general linear and quadratic coefficient regression and specific quadratic coefficient regression after each knot were fitted. The regression coefficients were estimated nested within sex of the calf in all situations. According to the F test for sum of squared residuals differences, the inclusion of the age of dam at calving × FH interaction did not improve the fit of the model and the CLA model provided the best fit. However, the estimates of the age of dam at calving and dam genetic group interaction from the CLA model for dam genetic group × sex of the calf classes with few records were not appropriate, but the estimates of the age of dam at calving and dam genetic group interaction from the FCh model for those classes were appropriate. The differences were small in the estimates of the age of dam of calving and dam genetic group interaction from the CLA or FCh models for dam genetic group × sex of the calf classes with many records.
3 citations
Cites background or methods from "Modeling the effect of the age of d..."
...The general form of the AOD effect in [1] defined in years with centesimal precision, was modeled by segmented polynomials with general linear and quadratic and specific quadratic effects, starting from the knots at 6.33 and 10.66 years of age, according to the recommendation by Toral et al. (2009)....
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...Additional information on this database can be obtained in Toral et al. (2009)....
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TL;DR: The interaction between the calf genetic group and its contemporary group is pointed out to represent a significant part of the variation observed for the weaning weight of the Charolais-Zebu crossbred calves, and the effects of alleles' percentage from theCharolais breed and the heterozygosity, individual and maternal can be modeled by using the multiple regression.
Abstract: This study was carried out to evaluate some alternatives for modeling of genetic and environmental effects influencing the weaning weight of Charolais-Zebu crossbred calves. The weaning weight data of 56,965 calves with alleles' percentage from the Charolais breed varying from 23% to 66% were used. The models under comparison differed for the inclusion of the individual and maternal additive and non-additive genetic effects, as well as the way to model those effects (multiple regression or discrete variable). The inclusion of the interaction between the calf genetic group and its contemporary group was also evaluated as a random uncorrelated effect. The adjustment criteria pointed out the interaction between the calf genetic group and its contemporary group to represent a significant part of the variation observed for the weaning weight of the Charolais-Zebu crossbred calves, and the effects of alleles' percentage from the Charolais breed and the heterozygosity, individual and maternal, can be modeled by using the multiple regression.
2 citations
01 Jan 2012
TL;DR: In this article, the degree of multicollinearity and the variables involved in linear dependence relations in additive-dominant models were assessed based on the variance inflation factor and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables.
Abstract: The objective of this work was to assess the degree of multicollinearity and to identify the variables involved in linear dependence relations in additive-dominant models. Data of birth weight (n=141,567), yearling weight (n=58,124), and scrotal circumference (n=20,371) of Montana Tropical composite cattle were used. Diagnosis of multicollinearity was based on the variance inflation factor (VIF) and on the evaluation of the condition indexes and eigenvalues from the correlation matrix among explanatory variables. The first model studied (RM) included the fixed effect of dam age class at calving and the covariates associated to the direct and maternal additive and non-additive effects. The second model (R) included all the effects of the RM model except the maternal additive effects. Multicollinearity was detected in both models for all traits considered, with VIF values of 1.03-70.20 for RM and 1.03-60.70 for R. Collinearity increased with the increase of variables in the model and the decrease in the number of observations, and it was classified as weak, with condition index values between 10.00 and 26.77. In general, the variables associated with additive and non-additive effects were involved in multicollinearity, partially due to the natural connection between these covariables as fractions of the biological types in breed composition.
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TL;DR: There was a significant interaction between cow age and period for milk production and between management and cow age for protein content, and adult cows showed higher ESD content, followed by the young cows, first calf and old cows.
Abstract: The objective of this work was to evaluate the production and composition of milk of beef cows of four genetic groups, including Charolais (C), Nellore (N), CN crossbreds daughters of C bulls, and NC crossbreds, daughters of N bulls, maintained on native pasture and submitted to different managements during pre-weaning: supplemented with rice bran (.7% of the body weight) and weaned at 42 or 63 days postpartum, or non supplemented and weaned at 63 days. The cow age varied from 3 to 12 years, being classified as: first calf, young, adult and old cows. The data were submitted to variance analysis, the statistic model included management, cow genetic group, cow age and period effects and the interactions among these factors. Lactose and fat contents were not influenced by the factors studied. There was a significant interaction between cow age and period for milk production and between management and cow age for protein content. Supplemented cows showed higher milk production (3.85 vs 3.25 L/day), total dry extract content - EST (12.18 vs 11.83%) and nonfat dry extract content - ESD (8.75 vs 8.57%). The milk production declined as the lactation period advanced, and the reduction was more accentuated in the non supplemented cows. CN crossbred cows produced more milk (4.17 L/day) than the straigthbreds, not differing from the NC crossbred (3.76 L/day). N cows showed milk production similar to the C cows, respectively, 3.16 and 3.11 L/day. However, N cows milk was of better quality, including protein (3.16 vs 2.86%), EST (12.52 vs 11.46%) and ESD (8.87 vs 8.49%). Adult cows showed higher ESD content, followed by the young cows, first calf and old cows, being 8.86; 8.62; 8.62 and 8.54%, respectively.
42 citations
TL;DR: The julian birth date is an important effect on ADG and should be included in the model and a segmented polynomial function may be preferable to a discrete parameterization.
Abstract: The objective of this work was to study the effects of age of dam (AOD), age of calf (AOC) and Julian date of birth (DOB) on the average daily gain (ADG) from birth to weaning period of Nellore breed animals. The data were analyzed by restricted maximum likelihood, using the animal model. The model included the direct effects of contemporary group (CG), AOD, AOC and DOB, and the direct effects (animal), maternal, permanent environmental and residue. The covariates were defined using segmented polynomials. In view of higher association between the AOC and DOB effects and of the importance of these effects on ADG, estimates with these two effects as a whole were selected. The correlation value between AOC and DOB of -0.60 was a poor indicator of the problems, being the three-dimensional plot very useful. The AGD was significantly influenced by linear and quadratic effects of calf age. The usual way to obtain adjusted weaning weights through AGD can not be adequate for this data set. The julian birth date is an important effect on ADG and should be included in the model and a segmented polynomial function may be preferable to a discrete parameterization.
11 citations
01 Jan 1996
6 citations
"Modeling the effect of the age of d..." refers background in this paper
...Further details on the growth traits of crossbred Charolais-Zebu calves can be obtained in Alencar et al. (1998) and Trematore et al. (1998)....
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Journal Article•
TL;DR: Os procedimentos de avaliacao genetica multirracial produzem predicoes geneticas aditivas mais acuradas, permitem a comparacao direta de animais de diferente composicao racial e viabilizam o melhoramento genetico aditivo e nao-aditivo em populacoes multirraciais.
Abstract: A disponibilidade de grandes bases de dados em associacoes de diferentes racas e cruzamentos de bovinos,e a demanda crescente dos produtores por avaliacoes geneticas dos animais de racas puras e cruzados tem renovado o interesse na implementacao de procedimentos de avaliacao genetica multirracial. Na maioria das associacoes de criadores dos Estados Unidos esta sendo aplicada a avaliacao genetica de animais puros e cruzados.O Brasil, com sua enorme populacao bovina (167 milhoes),composta amplamente por Zebu e seus cruzamentos (80%),e muitas grandes e bem estruturadas empresas (varias com dez mil animais ou mais), e provavel que possua um expressivo numero de bases de dados apropriadas para ser analisado por meio de procedimentos de avaliacao genetica multirracial. Comumente, no entanto, neste pais sao usados procedimentos de avaliacao genetica intra-racial independentemente da composicao genetica das populacoes bovinas. Os procedimentos intra-raciais ignoram os efeitos geneticos nao-aditivos entre racas, e assumem que os parâmetros geneticos sao os mesmos em todos os grupos raciais. Os procedimentos de avaliacao genetica multirracial incluem ambos os aspectos, assim, eles sao preferiveis aos intra-raciais para avaliar geneticamente populacoes compostas por animais puros e cruzados. Os procedimentos de avaliacao genetica multirracial produzem predicoes geneticas aditivas mais acuradas, permitem a comparacao direta de animais de diferente composicao racial e viabilizam o melhoramento genetico aditivo e nao-aditivo em populacoes multirraciais. No entanto, esses procedimentos sao computacionalmente mais complexos, requerem maior numero de parâmetros geneticos e apresentam problemas de confundimento e multi colinearidade. Neste artigo, caracterizam-se as populacoes multirraciais, discutem-se modelos de avaliacao genetica, procedimentos e tarefas para sua implementacao, e, quando relevante, apresentam-se comentarios gerais sobre a situacao multirracial no Brasil.
PALAVRAS-CHAVE: Bovinos, cruzamento, avaliacao genetica, multirracial, predicao.
6 citations
"Modeling the effect of the age of d..." refers background in this paper
...…matings of individuals with the same genetic composition and of some crosses, such as the F2, characterized an incomplete multiracial population (Elzo & Borjas, 2004), that can occur because, in this commercial population, the crossings are directed to produce animals with a predetermined…...
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