J.A.G. Bergmann

Genetic association among scrotal circumference and female reproductive traits in Nellore

The objectives of this work were to estimate of genetic parameters for scrotal circumference (SC) at 12 (SC12, n = 652) and 18 (SC18, n = 607) months of age, age at first calving (AFC, n = 1,582), first (FCD, n = 1,582) and second (SCD, n = 644) calving dates and first calving interval (FCI, n = 644) in Nellore cattle. Parameters were estimated using REML methodology, with animal models and considering the relations among 15,648 animals. Heritability estimates from univariate analyses were .24±.10, .31±.10, .01±.03, .11±.05, .07±.08 and .10±.10, respectively, for SC12, SC18, AFC, FCD, SCD and FCI. These values were close to the estimates from bivariate analyses, except for the analysis including both SC (heritability estimates of .61 and .68, respectively, for SC12 and SC18). Genetic correlation estimates between SC12 and, respectively, AFC, FCD, SCD and FCI were ¾1.00, -.08, -.71, and -.37. In the same order, genetic correlation between SC18 and female reproductive traits were ¾1.00, .21, -.35 and -.44. The selection for SC12 would be more effective than selection for SC18 when trying to improve the reproductive traits of the females.

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).

Heritability of scrotal circumference adjusted and unadjusted for body weight in nellore bulls, using univariate and bivariate animal models

Mixed model methodology under univariate and bivariate animal models was used to estimate genetic parameters of scrotal circumference (SC) unadjusted (h2U) and adjusted (h2A) for body weight, from field data on 875 Nellore males sired by 80 bulls. The models included random effect of animal, the fixed effects of age of dam, year of birth, and month and year of measurement, and the covariate age of the animal. In addition, one of the models also included the covariate body weight. Using univariate models, SC estimates of h2U were 0.18, 0.65, 0.77 and 0.60, and of h2A they were 0.15, 0.60, 0.71 and 0.50, at 9, 12, 18 and 24 m.o. of age, respectively. Bivariate estimates of heritability ranged from 0.18 to 0.77 for h2U, and from 0.13 to 0.70 for h2A. The results suggest that it would be better to consider unadjusted SC rather than adjusted SC in selection programs. Bivariate body weight estimates of heritability ranged from 0.15 to 0.45. Genetic correlations between SC and body weight ranged from 0.58 to 0.71 when body weight was not included in the model, and from 0.33 to 0.64 when body weight was included. These results suggest that simultaneous selection for body weight and SC is possible in Nellore cattle.

Interação genótipo-ambiente em algumas características produtivas de gado de corte no Brasil

The objective of this study was to measure the genotype-environment interaction (GEI) effect on some growth traits in Nellore cattle. Data from 2,896 records of pre-weaning (PW), 2,605 of weaning (WW) and 1,522 of post-yearling (YW) weights with a total of 9,911 pedigree animals from two farms of different regions of Minas Gerais State, South (farm I) and Northeast (farm II) were analyzed. Contemporary groups consider the effects of month-year of birth, sex, and herd. Only data from animals raised under pasture conditions were used. Covariance components were estimated by MTDFREML. Direct heritability obtained from bivariate analyses were 0.24, 0.16 and 0.17 (farm I) and 0.25, 0.24 and 0.17 (farm II) for PW, WW and YW, respectively. The ranking correlations between farms were 0.74, 0.76 and 0.51 and genetic correlations between farms were 0.96, 0.95 and 0.53 for PW, WW and YW, respectively. These results showed that there was no evidence of GEI up to weaning time but there was a significant effect of this interaction on the post-yearling weight. If selection criterion includes growth traits measured after weaning, regional evaluation should be recommended for bulls choice.

Heterogeneidade de variância e avaliação genética de bovinos da raça Holandesa no Brasil

Dados de 109.200 lactacoes foram utilizados para verificar o efeito da heterogeneidade de variância sobre a avaliacao genetica de vacas e touros da raca Holandesa criados no Brasil. A producao total de leite ajustada para idade adulta foi usada para classificar os rebanhos em tres classes de desvio-padrao fenotipico: baixo ( 1625 kg). Dados das primeiras lactacoes foram analisados considerando a producao total de leite ajustada para idade adulta (TOTAJU) e producao total de leite ajustada para idade adulta e para 305 dias de lactacao (TAJU305). As producoes de leite medias e os componentes de variância genetica, residual e fenotipica aumentaram com o aumento do desvio-padrao da classe. Para as classes de baixo e medio, baixo e alto e medio e alto desvios-padrao, as correlacoes geneticas foram 0,97; 0,89; e 0,91 para TOTAJU e 0,97; 0,92; e 0,96 para TAJU305, respectivamente. As correlacoes entre os valores geneticos para as classes de baixo, medio e alto desvios-padrao obtidos nas analises conjuntas (considerando como diferentes a expressao da caracteristica nas tres classes) e os obtidos na analise geral (todas as classes como unica caracteristica) foram proximas a unidade. Entretanto, os reprodutores apresentaram maiores valores geneticos em rebanhos das classes de alto desvio-padrao. Na avaliacao genetica, e importante considerar a variabilidade entre rebanhos, pois, sob selecao, as classes mais variaveis contribuiram com a maior parte dos animais, e a avaliacao genetica do animal poderia ser funcao nao apenas do seu potencial genetico, mas tambem do ambiente no qual suas progenies expressaram a caracteristica.

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

Estimates of genetic parameters for weaning weight adjusted to 240 days of age (WW240), age at first calving (AFC), age at second calving (ASC) and first calving interval (FCI) in Nellore cattle using REML methodology (MTDFREML), were obtained. Heritability estimates from univariate analyses were: 0.48±0.20; 0.27±0.15; 0.14±0.16; and 0.03±0.13, for WW240, AFC, ASC and FCI, respectively. Genetic correlation estimates between AFC and ASC and AFC and FCI were 0.97, -0.92, respectively. The genetic correlation between ASC and FCI was -0.82. The genetic correlations between WW240 and AFC, ASC and FCI were -0.20, 0.00 and 1.00, respectively.

Herdabilidade e correlação genética entre perímetro escrotal, libido e características seminais de touros Nelore

Dados de 273 touros Nelore nascidos de 1992 a 1998 e com idade media de 31 meses foram utilizados para estimar as herdabilidades do perimetro escrotal (PE), libido (Lib), motilidade (mot), vigor (vig), concentracao (con) e taxa de anormalidade seminal (ta) e as correlacoes geneticas entre essas caracteristicas. Com o uso do metodo da maxima verosimilhanca restrita as estimativas de herdabilidade e respectivos erros-padrao foram 0,38±0,20 para PE, 0,33±0,20 e 0,31±0,20 para Lib com idade ou peso corporal no modelo, respectivamente, 0,01±0,10 para mot, 0,03±0,30 para vig, 0,00±0,50 para coN e 0,07±0,13 para ta. As correlacoes geneticas entre PE e Lib foram 0,78 e 0,76, respectivamente, considerando-se ou nao o peso corporal no modelo. Correlacoes geneticas entre PE e as caracteristicas con, mot, vig e ta foram 0,99, 1,00, -0,14 e 0,99, respectivamente. Pode-se esperar resposta a selecao direta para PE e Lib e a selecao para uma das caracteristicas resultaria em selecao para a outra. As baixas estimativas de herdabilidade para as caracteristicas seminais indicam pequeno componente genetico aditivo.

Estimativas de componentes de (co)variância e herdabilidade direta e materna de pesos corporais em ovinos da raça Santa Inês

The objective of this work was to estimate the (co) variance components and direct and maternal heritability of the body weights of sheep of Santa Ines breed. A total of 3,771 lambs weights records of the Santa Ines hair sheep breed, progenies of 114 sires, and 758 ewes were analyzed, obtained from experimental herds of EMBRAPA - SNPA from 1985 to 1995. The covariance components and genetic parameters from additive genetic effects, maternal and permanent environmental effects, as well as the covariance between those effects for birth weight (BW), weight at 112 (W112) and weight at 196 days of age (W196), were estimated by Restricted Maximum Likelihood (REML) using MTDFREML program, under animal model. Including or not the maternal genetic effect or permanent environmental effect, as well as the genetic covariance between the direct and maternal effects, five different animal models were used to determine the most appropriate model for each trait. In general, the most comprehensive model (Model 4) was the one that presented the greatest value for the maximum log likelihood function (log of L) for all studied traits. When maternal effects were excluded, estimates of direct heritabilities were substantially inflated (.31 to .37). The maternal effects were important for all traits, even those that were measured after weaning. Genetic correlation between direct and maternal effects for BW and W112 were negative and low (from -.31 to -.10), however, for W196 this value was positive and high (from .67 to .98). The exclusion of the maternal effects, when they are important, resulted in overestimates of heritability.

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.

Genetic parameters for body weight and real-time ultra sound carcass traits of Guzera cattle

Genetic parameters were estimated for body weight and real-time ultra-sound loin-eye area, rump fat thickness, and back fat thickness using data from 1,325 yearling Guzera cattle (90.4% bulls and 9.6% heifers) and pedigree structure with 6,642 animals. Variance and covariance components were estimated using REML methodology and MTDFREML software. Single trait animal models were used to estimate repeatability and heritability for the four traits. Multiple traits animal models were used to estimate genetic correlations among the traits. Repeatability estimates (standard errors) were 0.44(0.10) for body weight, 0.39(0.10) for loin-eye area, 0.75(0.06) for rump fat thickness, and 0.49(0.08) for back fat thickness. Heritability estimates were 0.42(0.11) and 0.41(0.11) for body weight, 0.35(0.09) and 0.34(0.09) for loin-eye area, 0.20(0.08) and 0.32(0.08) for back fat thickness, and 0.05(0.06) and 0.10(0.08) for rump fat thickness, respectively from single and multiple traits models. Genetic correlation estimates were 0.79(0.09) between body weight and loin-eye area, 0.20(0.08) between body weight and back fat thickness, 0.05(0.06) between loin-eye area and rump fat thickness, 0.02(0.27) between loin-eye area and back fat thickness and 0.64(0.22) between the two measurements of fat thickness. In order to evaluate carcass traits, results suggested that repeated real-time ultra-sound measurements are not needed and that direct selection for these traits might be effective. In addition, there is no genetic antagonism between selection for body weight and carcass traits.