Journal Article•
Perspectivas da avaliação genética multirracial em bovinos no brasil
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.
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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.
5 citations
Cites background from "Perspectivas da avaliação genética ..."
...…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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TL;DR: The influence of environmental parameters on the physiological responses of purebred and crossbred Nellore calves born in a subtropical region was studied and PT level was significantly higher in NR calves than in NI ones.
Abstract: Estudou-se a influencia de fatores climaticos sobre as respostas fisiologicas de bezerros, puros e cruzados, filhos de vacas da raca Nelore ou de alta mesticagem de Nelore acasaladas com touros das racas Aberdeen Angus (AN), Simental (SN), Canchim (CN) e Nelore (NI e NR). Os bezerros AN, SN, CN e NI foram mantidos em sistema rotacionado intensivo, enquanto o grupo NR foi mantido em sistema extensivo. Os bezerros foram observados de forma direta desde o nascimento ate a primeira mamada, medindo-se a latencia para a primeira mamada (LM). Aproximadamente 24 horas apos o parto, coletaram-se amostras de sangue do bezerro para as dosagens de proteina total (PT), glicose (Gli), triiodotironina (T3), tiroxina (T4), relacao T4:T3, cortisol (Cort) e imunoglobulina G (IgGb), alem das medidas de temperatura retal do bezerro (TR) e dos pesos de vacas e bezerros. Para analise dos efeitos de clima, foram tomadas no dia do nascimento as medidas de temperatura do ar (Temp), umidade do ar (UR) e precipitacao (PRE). Os parâmetros fisiologicos foram estudados pelo metodo dos quadrados minimos com modelos que incluiram os efeitos de ano e mes de nascimento, grupo e sexo do bezerro, categoria da vaca e hora do parto e das interacoes ano × grupo e ano × mes de nascimento, alem das covariaveis peso do bezerro, PRE, Temp, UR e LM. Temp mostrou efeito significativo para as concentracoes de T3, T4, T4:T3 e de Cort. Quanto maior Temp, menores as concentracoes de T3 e de Cort e maiores as de T4 e de T4:T3. LM influenciou os niveis de Cort, PT e IgGb, de modo que, quanto maior LM, maior a concentracao de Cort e menor as de IgGb e PT. Tambem houve efeito significativo de grupo do bezerro sobre PT, que foi maior nos bezerros NR que nos bezerros NI.
2 citations
01 Jun 2011
TL;DR: In this article, the influence of some non-genetic factors on birth (BW) and weaning weight corrected to 205 d (WWA) of Angus calves, 1,999 and 1,574 weights were analyzed.
Abstract: To determine the influence of some non-genetic factors on birth (BW) and weaning weight corrected to 205 d (WWA) of Angus calves, 1,999 and 1,574 weights were analyzed. All the animals were grazing and they were vaccinated against enzootic every six months. The data was analyzed using an analysis of variance under least squares methodology and the statistical model included: year of birth (YB = 1991-2007), season of birth (SB = Cold, Dry and Rainy), parity number (PN = 1, 2, 3,… ≥9 calving) and sex (SX = Males and Females) and the interactions YB*SB, YB*PN and YB*SX. All effects and the interactions affected BW and WWA (P<0,01). The means and standard deviation were 36.2 ± 2.6 and 186.8 ± 30.0 kg, respectively. The differences between the best years (2007) and worse year (1991) to BW was 1.1 kg. Cows of 1, 2 and ≥9 calving had calves less heavy. Male calves weighted more than female to birth and weaning. The interactions that involved YB indicate that the direction and magnitude of the effects are not constant within every year. The interaction YB*SB, YB*PN and YB*SX were important on WWA without being possible to define some tendency or magnitude. All the environmental effect studied was important.
2 citations
Journal Article•
TL;DR: Multibreed genetic evaluation models allow the prediction of animal breeding values in a population of animals of various breed compositions to yield additive and nonadditive animal genetic values, which allow more precise selection decisions and mating plans.
Abstract: Multibreed genetic evaluation models allow the prediction of animal breeding values in a population of animals of various breed compositions. The structure of this type of model depends on the traits to be evaluated and the multibreed population to be analyzed, and they eventually yield additive and nonadditive animal genetic values, which allow more precise selection decisions and mating plans.
1 citations
01 Jun 2011
TL;DR: In this article, the influence of some non-genetic factors on birth and weaning weight corrected to 205 d (WWA) of Angus calves, 1,999 and 1,574 weights were analyzed.
Abstract: To determine the influence of some non-genetic factors on birth (BW)
and weaning weight corrected to 205 d (WWA) of Angus calves, 1,999 and
1,574 weights were analyzed. All the animals were grazing and they were
vaccinated against enzootic every six months. The data was analyzed
using an analysis of variance under least squares methodology and the
statistical model included: year of birth (YB = 1991-2007), season of
birth (SB = Cold, Dry and Rainy), parity number (PN = 1, 2, 3,…
≤9 calving) and sex (SX = Males and Females) and the interactions
YB x SB, YB x PN and YB x SX. All effects and the interactions affected
BW and WWA (P <0,01). The means and standard deviation were 36.2
± 2.6 and 186.8 ± 30.0 kg, respectively. The differences
between the best years (2007) and worse year (1991) to BW was 1.1 kg.
Cows of 1, 2 and ≤9 calving had calves less heavy. Male calves
weighted more than female to birth and weaning. The interactions that
involved YB indicate that the direction and magnitude of the effects
are not constant within every year. The interaction YB x SB, YB x PN
and YB x SX were important on WWA without being possible to define some
tendency or magnitude. All the environmental effect studied was
important.
1 citations
References
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TL;DR: Extension of beef cattle genetic evaluation procedures to multibreed data sets is proposed as a way to allow inclusion of crossbred animals into current analyses and to provide comparisons between purebred animals of different breeds.
Abstract: Extension of beef cattle genetic evaluation procedures to multibreed data sets is proposed as a way to allow inclusion of crossbred animals into current analyses and to provide comparisons between purebred animals of different breeds. Previous papers dealing with multibreed BLUP have proposed sire or sire-maternal grandsire models. Because current models used in the beef industry are predominantly of the reduced animal model form, models were developed for animal model and reduced animal model mixed-model evaluations that would account for fixed and random additive genetic effects, along with fixed and random nonadditive genetic effects for populations with heterogeneous means and variances.
62 citations
TL;DR: Estimates of genetic variation and predictions of expected progeny differences showed that Romosinuano animals competed well against Zebu and RZ crossbred animals under the tropical environmental conditions at Turipaná.
Abstract: Intrabreed additive genetic, environ- mental, and phenotypic variances and covariances for Romosinuano ( R ) and Zebu (Z), as well as interbreed nonadditive genetic variances and covariances (sire × breed-group-of-dam interactions), for birth weight (BWT), weaning weight (WW), and postweaning gain (GW) were computed using a Romosinuano-Zebu multibreed data set from the TuripanaExperiment Station in Colombia. Covariances were estimated with a sire-maternal grandsire model, using a multibreed REML procedure. The computing algorithm was a generalized expectation-maximization (GEM) al- gorithm. This algorithm yields no asymptotic standard errors as part of its computations. Because of the small size of the data set (2,546 calves), these REML covariance estimates should be viewed with caution. Estimates of intrabreed heritabilities were similar to the ratios of interbreed nonadditive to phenotypic variances (interactibilities) for direct and maternal effects of the growth traits evaluated in this study. Intrabreed heritability estimates for BWT, WW, and GW direct genetic effects were .16, .09, and .14, for R and .24, .10, and .14 for Z. Corresponding heritability values for maternal effects were .18, .09, and .23 for R and .14, .13, and .07 for Z. Interactibility estimates were .21, .05, and .12, for direct and .26, .04, and .11, for maternal BWT, WW, and GW. Negative correla- tions between additive maternal weaning weight and direct and maternal postweaning gain, as well as between environmental weaning weight and post- weaning gain, suggested that there was compensatory postweaning gain in this herd. Estimates of genetic variation and predictions of expected progeny differ- ences showed that Romosinuano animals competed well against Zebu and RZ crossbred animals under the tropical environmental conditions at Turipana ´ .
55 citations
TL;DR: The MBAM represents a viable alternative to AM for multiple-breed genetic evaluations, providing the necessary flexibility in modeling heteroskedastic genetic variances of breed composition groups.
Abstract: The primary objective of this study was to demonstrate the utility of a hierarchical Bayes implementation of a multiple-breed animal model (MBAM) to estimate breed composition means and additive genetic variances as well as on variances due to the segregation between breeds. The MBAM and a conventional animal model (AM) were both applied to five simulated data sets derived from each of two different populations. Population I consisted of crosses between two breeds having a twofold difference in genetic variance and a nonzero segregation variance. Population II had the same population structure as Population I, except that the two breeds had the same genetic variance with no segregation variance; that is, Population II was essentially single breed in its genetic architecture. For Population I, posterior means of all variance components obtained by MBAM were unbiased, with 95% posterior probability intervals (PPI) having the expected coverage based on five replicates. The MBAM showed a slightly superior performance over the AM for genetic predictions in Population I, although there was no evidence that the use of the MBAM translated into greater genetic gains relative to the use of the AM. Nevertheless, the MBAM was clearly demonstrated to have superior fit to the data using pseudo-Bayes factors (PBF) as the basis for model choice. As expected, the MBAM and AM performed equally well in Population II. A data set consisting of 22,717 postweaning gain (PWG) records of a Nelore-Hereford population (40,082 animals in the pedigree) also was analyzed. The MBAM inference on Nelore and Hereford additive heritabilities (h 2 A) substantially differed. Herefords had a posterior mean h 2 A of 0.20 with a 95% PPI of 0.15 to 0.25, whereas the corresponding values for the Nelores were 0.07 and 0.04 to 0.11, respectively. The posterior mean genetic variance due to the segregation between these breeds was 8.4 kg2, with a 95% PPI of 2.3 to 24.8 kg2, and represented 35.4% of the Nelore but only 9.9% of the Hereford posterior mean genetic variance. The posterior mean h 2 A using the AM was 0.15, presumed common across the two breeds, with a 95% PPI of 0.11 to 0.19. The PBF heavily favored the MBAM over the AM for the PWG data. Accordingly, the MBAM represents a viable alternative to AM for multiple-breed genetic evaluations, providing the necessary flexibility in modeling heteroskedastic genetic variances of breed composition groups.
51 citations
TL;DR: Selection for carcass traits within desirable (narrow) ranges and slaughter of steers at similar compositional end point seems to be a good combination to help produce meat products of consistent quality.
Abstract: Estimates of covariances and sire expected progeny differences of additive and nonaddi- tive genetic effects for six carcass traits were obtained using records from 486 straightbred and crossbred steers from 121 sires born between 1989 and 1995 in the Angus-Brahman multibreed herd of the University of Florida Steers were slaughtered at a similar carcass composition end point Covariances were estimated by REML procedures, using a generalized expectation-maximization algorithm applied to mul- tibreed populations Straightbred and crossbred esti- mates of heritabilities and additive genetic correla- tions were within ranges found in the literature for steers slaughtered on an age- or weight-constant basis for hot carcass weight, longissimus muscle area, and shear force but equal to or less than the lower bound of these ranges for fat-related traits Maximum values of interactibilities (ie, ratios of nonadditive variances to phenotypic variances in the F1) and nonadditive genetic correlations were smaller than heritabilities and additive genetic correlations in straightbreds and crossbred groups Sire additive and total direct genetic predictions for longissimus muscle area, marbling, and shear force tended to decrease with the fraction of Brahman alleles, whereas those for hot carcass weight and fat thickness over the longissimus were higher, and those for kidney fat were lower in straightbreds and F1 than in other crossbred groups Nonadditive genetic predictions were similar across sire groups of all Angus and Brahman fractions These results suggest that slaughtering steers on a similar carcass composition basis reduces variability of fat-related traits while retaining variability for non-fat-related traits comparable to slaughtering steers on a similar age or weight basis Selection for carcass traits within desirable (narrow) ranges and slaughter of steers at similar compositional end point seems to be a good combination to help produce meat products of consis- tent quality
43 citations
Journal Article•
TL;DR: Recursion procedures to directly compute G −1 in multibreed populations were developed because of the heterogeneity of variances and covariances across breed groups.
Abstract: Multiple-trait, multibreed mixed model procedures require the inverse of a multiple-trait heterogeneous covariance matrix of direct and maternal additive genetic effects (G −1 ). Because of the heterogeneity of variances and covariances across breed groups, recursive procedures used in single-breed populations cannot be used. Thus, recursive procedures to directly compute G −1 in multibreed populations were developed
36 citations