J.C.C. Pereira

Análise de alguns critérios de seleção para características de crescimento na raça Nelore

Foram obtidas estimativas de parâmetros geneticos para peso ao nascimento (PN) e ao sobreano (PSOB), ganhos de peso pre- (GPNDES) e pos-desmama (GP345), dias para 160 (D160) e 300kg (D300) de peso vivo, e taxas de crescimento relativo pre- (TCR1) e pos-desmama (TCR2), utilizando 60.470 animais Nelore. Adotou-se o metodo REML, sob modelo animal. Para caracteristicas pre-desmama (PN, GPNDES, D160 e TCR1), o modelo incluiu efeitos aleatorios de animal, aditivo materno, de ambiente permanente de vaca e de residuo, e os efeitos fixos de grupo de contemporâneos (GC) a desmama e das covariaveis idade da vaca ao parto e idade do animal (IA) a epoca da desmama. Para caracteristicas pos-desmama (PSOB, GP345, D300 e TCR2), considerou-se como efeito fixo o GC ao sobreano e como covariavel a IA ao sobreano. As medias observadas± desvios-padrao foram 30,7±3,8kg (PN); 317,2± 49,4kg (PSOB); 155,4± 21,0kg (GPNDES); 119,6± 32,2kg (GP345); 175,7± 34,2 dias (D160); 553,9± 152,7 dias (D300); 913,2± 80,9x10-3%/dia (TCR1); e 140,5± 31,2x10-3%/dia (TCR2). Resultantes das analises conjuntas de duas caracteristicas (GPNDES e cada uma das outras caracteristicas), as estimativas de herdabilidade direta e materna para GPNDES variaram, respectivamente, de 0,11 a 0,20 e de 0,03 a 0,16. Os coeficientes de herdabilidade direta foram 0,24; 0,26; 0,18; 0,15; 0,12; 0,14 e 0,22, respectivamente, para PN, PSOB, GP345, D160, D300, TCR1 e TCR2. Os coeficientes de herdabilidade materna para PN, D160 e TCR1 foram, respectivamente, 0,11; 0,00 e 0,14. As correlacoes geneticas entre GPNDES e as outras caracteristicas foram altas, exceto entre GPNDES e GP345 (0,23).

Associação entre medidas lineares e angulares de equinos da raça Mangalarga Marchador

The effects of State and stud of origin, management (on pasture or in stable), gender, and age on morphometrics traits (measurements of 12 bone segments, 11 joint angles, two perimeters, and two heights) of 169 Mangalarga Marchador horses (82% females) raised in 11 herds of Minas Gerais and five from Sao Paulo State, were evaluated using the least squares methodology. In addition, residual phenotypic associations among these traits were measured. Statistical models did not fit well the observed variation, with coefficients of determination varying from 0.09 to 0.48 for linear and from 0.11 to 0.44 for angular traits. State and stud of origin, gender, age, and management were important sources of variation, respectively on 13 (48.1%), 12 (44.4%), six (22.2%), four (11.1%), and three (11.1%) of the 27 evaluated traits. Residual correlations between traits indicated that selection of animals with longer humerus was associated to animals with longer front and rear leg bone segments and higher wither and croup heights and larger crop and cannon perimeters. Also, selection of animals with larger fetlock and coronet-horizontal line angles will positively reflect on the wither and croup heights of the animals.

Estruturas de covariância de peso em função da idade de animais Nelore das regiões Sudeste e Centro-Oeste do Brasil

Body weight records from 90 to 450 days of age of Nellore animals from the Southeast and Center West of Brazil were used do estimate covariance structures of age dependent random effects for each region using random regression models. Covariance components of the regression coefficients were estimated by EMREML using the software REML90. The fixed effects of contemporary groups and additive genetic, additive maternal and permanent environment random effects were modeled by quadratic Legendre polynomials. The comparisons included structures of covariance and correlation of random effects, direct and maternal heritabitability and the ratio between genetic variances from different regions. The heritability, covariance and correlation structures showed similar patterns for both regions. Residual variance and permanent environment variances were smaller for Center West region as well as the maternal genetic additive from 150 to 400 days of age. Fixed effect trajectories in function of age of different contemporary groups showed different patterns, suggesting the necessity of specific set of regression coefficient estimates for each contemporary group. The maternal additive genetic variance showed higher heterogeneity between regions than the direct additive genetic variance.

Estimativas de herdabilidade e correlações fenotípicas, genéticas e de ambiente entre algumas características reprodutivas e produção de leite na raça Gir

Os objetivos deste estudo foram estimar herdabilidades e correlacoes fenotipica, genetica e de ambiente entre producao de leite (PL), idade ao primeiro parto (IPP) e intervalo de partos (IDP) na raca Gir, com emprego de analises uni e bicaracteres sob o metodo da maxima verossimilhanca restrita, por meio de algoritmo livre de derivadas (MTDFREML), ajustando modelos-animal. O modelo matematico para estudar a PL incluiu os efeitos fixos de rebanho-ano de parto e epoca de parto e idade ao parto como covariavel (linear e quadratica) e, alem do residuo, os efeitos aleatorios de animal e ambiente permanente. Para a IPP o modelo incluiu os efeitos fixos rebanho-ano de nascimento e epoca de nascimento, e efeito animal como aleatorio. O modelo adotado para estudar IDP contemplou os efeitos fixos rebanho-ano de parto e epoca de parto e idade da vaca ao parto como covariavel, e mais os efeitos aleatorios de animal, ambiente permanente e residuo. Por meio de analises bicaracteres, as estimativas de herdabilidade foram, respectivamente: PL1 e IPP = 0,25 e 0,18; PL1 e IDP1 = 0,27 e 0,07; PL2 e IDP2 = 0,20 e 0,05; PL3 e IDP3 = 0,17 e 0,05. As estimativas de correlacoes fenotipica, genetica e de ambiente foram, respectivamente: PL1 e IPP = 0,02, -0,29 e 0,11; PL1 e IDP1= 0,23, 0,52 e 0,19; PL2 e IDP2 = 0,26, 0,54 e 0,23; PL3 e IDP3 = 0,25, 0,13 e 0,27.

Curvas de lactação de vacas F1 Holandês-Gir ajustadas pela função gama incompleta

Estudaram-se o padrao das curvas de lactacao de 5.368 vacas F1 Holandes-Gir pelo modelo gama incompleto e os efeitos da ordem de lactacao e epoca de paricao sobre os parâmetros da funcao e sobre a producao inicial (PI), producao no pico de lactacao (PP), tempo ao pico de lactacao (TP), persistencia (PER) e producao total de leite estimada na lactacao (PLTLE). As curvas de lactacao apresentaram-se curvilineas com queda da producao a partir do inicio da lactacao. A diferenca entre a producao de multiparas e primiparas foi de 48,9%, favoravel as primeiras. As multiparas apresentaram maior queda na producao no primeiro mes de lactacao e maior persistencia, enquanto as primiparas apresentaram fortes quedas ao longo de toda lactacao e menor persistencia. A diferenca da producao de leite entre lactacoes iniciadas na epoca seca e das aguas foi de 1,6%, favoravel a primeira. Os resultados para producao relativa mensal, queda percentual na producao referente ao mes anterior e queda percentual na producao referente ao primeiro mes de lactacao indicam poucas diferencas no formato das curvas de lactacao para vacas paridas nas epocas da seca e das aguas. Baixos valores de R2 encontrados indicam que a funcao nao produziu bom ajuste para a curva de lactacao de vacas desse grupo genetico.

Análise genética de características ponderais e reprodutivas de fêmeas bovinas Tabapuã

Foram estudadas 1251 informacoes referentes aos pesos as idades-padrao de 205 (P205), 365 (P365) e 550 (P550) dias e idade ao primeiro parto (IPP) e primeiro intervalo de partos (IEP1) de femeas bovinas da raca Tabapua. As medias, desvios-padrao e coeficientes de variacao foram respectivamente: P205 - 173,9kg, 16,0kg e 9,2%; P365 - 225,7kg, 28,7kg e 12,7%; P550 - 277,0kg, 36,7kg e 13,3%; IPP - 1125,5 dias, 106,6 dias e 9,5% e IEP1 - 522,2 dias, 106,2 dias e 20,7%. As estimativas de componentes de (co)variância e de parâmetros geneticos foram obtidas pelo metodo de maxima verossimilhanca restrita, utilizando-se o software MTDFREML. Para cada caracteristica as estimativas de herdabilidade foram de 0,16, 0,25, 0,29, 0,03 e 0,01, na mesma ordem de citacao acima. As correlacoes geneticas entre as caracteristicas ponderais e reprodutivas foram: -0,67 (P205×IPP); -0,07 (P365×IPP); -0,41 (P550×IPP); 0,19 (P205×IEP1); 0,79 (P365×IEP1) e 0,64 (P550×IEP1).

Componentes de (co)variância e parâmetros genéticos de características de crescimento da raça Simental no Brasil

Birth, 100-day, weaning and yearling weights of 7587 Simmental cattle, and 25,812 pedigree data were used to estimate genetic parameters using different animal models. The simplest model (model l) included additive genetic and residual random effects. Models 2 and 3 were the same as model 1, but included, respectively, maternal permanent and maternal genetic effects. Model 4 did not include permanent effect. The most complete model (model 6) also included maternal additive and permanent effects, assuming covariance between them. Model 5 was the same as model 6, but did not included direct maternal covariance. Contemporary groups considered animals born in the same herd, year and season, from the same sex and raised under the same nutritional system. The models were compared using likelihood ratio tests. The (co)variance components and the genetic parameters decreased from the most simple (model 1) to the most complete model (model 6). One-hundred-day weight showed no (.00±.00) maternal genetic variance but moderate maternal environmental permanent effect (.17±.07). The maternal effects were important (P<.01) from birth to yearling. Maternal effects were important for weight traits of Simmental cattle and should be considered in genetic evaluations. However, comparing the values of maternal effects from models with and without permanent effects suggest confounding between these effects.

Critérios de seleção para características de crescimento em bovinos da raça Nelore

Data records of 28,050 animals from Nellore breed were used to compare selection criteria for beef cattle based on weight gain from birth to weaning (GBW), number of days to gain 160kg during the pre-weaning period (D160), daily weight gain from weaning to 18 months (GW18) and number of days to gain 240kg during the pos-weaning period (D240). Direct heritability estimates of GBW (.20) and D160 (.19) were similar while the direct heritability estimate of GW18 (.07) was larger than D240 (.03). Maternal heritability estimate of D160 (.16) was larger than maternal heritability of GBW (.06). High and negative correlation (-.95) was observed between GBW and D160. The association between maternal effect of GBW and direct effect of GW18 was positive (.33) while null correlation estimate betweeen D160 and D240 was observed for direct genetic effect. According to the estimated genetic parameters growth rate can be changed by both selection criteria (BBW and D160), during the pre-weaning period, although both selection criteria would not select the same animals, mainly if the selection criteria were based on maternal genetic effect during pre-weaning period and the direct genetic effect during the pos-weaning period. Maternal effect was not an important selection criterion for the studied traits. The low estimated correlations between pairs of traits for the pre and pos-weaning periods, also suggest that the selection criterion for each period, based on the studied traits, can be chosen independently.

Tendência genética de medidas lineares de pôneis da raça Brasileira

Data from 2073 Brasileira pony horses, born from 1974 to 1994, were used to predict breeding values and to study genetic trends of 10 linear traits. Derivative free restricted maximum likelihood methodology and MTDFREML algorithm were used for breeding value predictions. Genetic trend was accessed using weighted least squares estimates for regression coefficients of average breeding values on year of birth. Genetic trends were present (P<.01) in seven of the 10 traits. For each year there was a reduction of .070cm in withers and croup heights, .037cm in head length, .025cm in neck length, .023cm in croup length, .073cm in body length and .004cm in head width. Results indicated proportional body reduction of the Brasileira pony breed.

Estudo genético-quantitativo de características de crescimento na raça Tabapuã

The variance and covariance components, heritability for direct and maternal effects, correlations between direct and maternal effects and permanent environmental component of variance were estimated, using the REML methodology for birth weight (BW), weaning weight adjusted for 205 days (W205), weights at 365 (W365) and at 550 (W550) days of age in Tabapua animals. Maternal effect and the association between direct and maternal effects on growth traits were estimated. Animal records from 1978 to 2002 are from Fazenda Agua Milagrosa, located at Sao Paulo State. The direct and maternal heritability were, respectively, 0.32, 0.10; 0.20, 0.17; 0.21, 0.06 and 0.16; 0.03, for birth weight, weaning weight, weights at 365 and at 550 days of age. The correlations between direct and maternal effects for the same sequence of weights were -0.10; -0.20; -0.11 and -0.15. The fractions of permanent environmental of the phenotypic variance were 1.41x10-6; 2.5x10-7; 2,4x10-7 and 4.0x10-6. The inclusion of maternal effect is recommended for growth traits evaluation of Tabapua animals for selection purpose.