Genetic and environmental effects on tonic immobility duration of red-winged tinamou applying survival analysis

Fear behavioral studies provide knowledge on animal welfare, and fearful behaviors can be used as selection criteria of individuals adapted to intensive rearing system. The survival analysis methodology was applied to estimate tonic immobility (TI) duration, as an indicator of fear, of red-winged tinamous (Rhynchotus rufescens) reared in captivity and to determine if TI is genetically influenced. A number of 539 birds born between 2006 and 2010 were evaluated. The exploratory data analysis was performed using the Kaplan-Meier estimate (KM), and the covariates were then fit to a Cox model, considering month of observation nested within year of birth and body weight as fixed effects and the random effect of sire as frailty term. In order to predict genetic values and to estimate heritability, the model of proportional hazards was applied, using a Weibull distribution as the baseline hazard. Birds born in the last year presented shorter TI duration than those born in the previous year, as shown by the survival KM curves, indicating a decline in fearfulness from one year to the next. The Cox analysis detected that hazard function was reduced as body weight increased. The frailty term was significant (p<0.05), showing that sires induced variation in the TI duration of the offspring. Heritability estimated as 0.37, indicating the influence of additive genes. These findings suggest that the selection of for short TI duration may allow reducing fearfulness of a red-winged tinamou population after some generations.

Genetic and environmental effects on tonic immobility duration of red-winged tinamou applying survival analysis

Fear behavioral studies provide knowledge on animal welfare, and fearful behaviors can be used as selection criteria of individuals adapted to intensive rearing system. The survival analysis methodology was applied to estimate tonic immobility (TI) duration, as an indicator of fear, of red-winged tinamous (Rhynchotus rufescens) reared in captivity and to determine if TI is genetically influenced. A number of 539 birds born between 2006 and 2010 were evaluated. The exploratory data analysis was performed using the Kaplan-Meier estimate (KM), and the covariates were then fit to a Cox model, considering month of observation nested within year of birth and body weight as fixed effects and the random effect of sire as frailty term. In order to predict genetic values and to estimate heritability, the model of proportional hazards was applied, using a Weibull distribution as the baseline hazard. Birds born in the last year presented shorter TI duration than those born in the previous year, as shown by the survival KM curves, indicating a decline in fearfulness from one year to the next. The Cox analysis detected that hazard function was reduced as body weight increased. The frailty term was significant (p<0.05), showing that sires induced variation in the TI duration of the offspring. Heritability estimated as 0.37, indicating the influence of additive genes. These findings suggest that the selection of for short TI duration may allow reducing fearfulness of a red-winged tinamou population after some generations.(AU)

Evaluation of body weight and visual scores for genetic improvement of Nelore cattle.

The aims of our study were to estimate genetic parameters for body weight and visual scores and to evaluate their inclusion as selection criteria in the Nelore breeding program in Brazil. The traits studied were the body weight adjusted to 210 (W210) and to 450 (W450) days of age and visual scores for body structure, finishing precocity, and muscling evaluated at weaning (BSW, FPW, and MSW) and yearling (BSY, FPY, and MSY) ages. A total of 33,242, 26,259, 23,075, and 26,057 observations were considered to analyze W210, W450, and visual scores at weaning and yearling. The significant (P < 0.05) fixed effects for all traits were farm, birth season, birth year, sex, and management group. Single-trait analyses were performed to define the most fitting model to our data using the average information restricted maximum likelihood algorithm, for weaning traits. Subsequently, these models were used in single- and two-trait analyses considering the Bayesian inference algorithm. Two-trait Bayesian analyses resulted in average direct heritability estimates for BSW, FPW, MSW, W210, BSY, FPY, MSY, and W450 of 0.28, 0.30, 0.27, 0.28, 0.40, 0.44, 0.39, and 0.50, respectively. Genetic correlations varied from 0.40 to 0.96. Benefits to animal performance can best be achieved by considering body structure, finishing precocity, and muscling as selection criteria in the Nelore breeding programs. The decision to use visual scores measured at weaning should be considered in order to decrease generation interval and assist pre-selecting individuals, expecting carcass improvements in the future progeny.

Effect of litter substrates on the performance, carcass traits, and environmental comfort of red-winged tinamou (Rhynchotus rufescens)

The study aimed at evaluating the effect of litter substrates on the performance, carcass traits, and environmental comfort of red-winged tinamou (Rhynchotus rufescens). In this experiment, 160 birds, with 100 and 300 days of age, were housed into 20 pens, and distributed according to a completely randomized experimental design into five treatments with four replicates of eight birds each. Treatments consisted of five litter substrates: wood shavings, rice husks, peanut hulls, grass hay, or sand. Feed intake; weight gain; breast, hock, and footpad lesions; back feathering; total meat production; carcass and parts yield; and leukocyte counts were evaluated. Litter substrates were analyzed for dry matter content, standard microbial count, ammonia volatilization potential, water content, water holding capacity, temperature, and radiant heat load. The results showed that litter substrate did not influence the evaluated bird parameters, despite the higher microbial counts and released ammonia values determined in peanut hulls and sand, respectively. Sand also tended to have higher average temperature than the other litter substrates. It was concluded that litter substrate should be chosen at farmer discretion, taking into consideration its cost and utilization after use.(AU)

Effect of litter substrates on the performance, carcass traits, and environmental comfort of red-winged tinamou (Rhynchotus rufescens)

The study aimed at evaluating the effect of litter substrates on the performance, carcass traits, and environmental comfort of red-winged tinamou (Rhynchotus rufescens). In this experiment, 160 birds, with 100 and 300 days of age, were housed into 20 pens, and distributed according to a completely randomized experimental design into five treatments with four replicates of eight birds each. Treatments consisted of five litter substrates: wood shavings, rice husks, peanut hulls, grass hay, or sand. Feed intake; weight gain; breast, hock, and footpad lesions; back feathering; total meat production; carcass and parts yield; and leukocyte counts were evaluated. Litter substrates were analyzed for dry matter content, standard microbial count, ammonia volatilization potential, water content, water holding capacity, temperature, and radiant heat load. The results showed that litter substrate did not influence the evaluated bird parameters, despite the higher microbial counts and released ammonia values determined in peanut hulls and sand, respectively. Sand also tended to have higher average temperature than the other litter substrates. It was concluded that litter substrate should be chosen at farmer discretion, taking into consideration its cost and utilization after use.

Body condition score in ruminants / Escore de condição corporal em ruminantes

The measurement of body condition score in ruminants has been recommended in several studies because this score reflects the metabolic status of the animal, indicating individuals that are less susceptible to diseases, those more able to reproduce and the ones with better carcass yield. Thus, the routine assessment of body condition score (BCS) of females should contribute to increase the profitability of the production system, since potential problems can be controlled before they significantly reduce profitability. The methodologies proposed initially to measure BCS were improved over time, according to the economic purpose of raising ruminant species and the phenotypic particularities of small ruminants. The researches show the benefits provided by the measurement of BCS on the traits related to health, reproduction, production, maternal ability, carcass and feed consumption of ruminants. Moderate values of BCS reflect a metabolic balance, resulting in better reproductive performance, increased milk production, good development of the offspring and good carcass quality.

A aferição da condição corporal de ruminantes tem sido recomendada em diversos estudos por refletir o estado metabólico do animal, indicando os indivíduos menos susceptíveis a doenças, mais aptos à reprodução e de melhor rendimento de carcaça. Assim, a avaliação rotineira do escore de condição corporal (ECC) de fêmeas deve contribuir para maior rentabilidade do sistema de produção, pois potenciais problemas podem ser controlados antes que reduzam significativamente a mesma. As metodologias propostas inicialmente para mensurar o ECC foram aprimoradas no decorrer do tempo, tendo em vista o propósito de criação dos ruminantes e as particularidades fenotípicas dos pequenos ruminantes. As pesquisas evidenciam os benefícios proporcionados pela aferição do ECC nas características ligadas à sanidade, reprodução, produção, habilidade materna, consumo alimentar e carcaça de ruminantes. Valores moderados de ECC refletem o equilíbrio metabólico, garantindo melhor desempenho reprodutivo, maior produção de leite, bom desenvolvimento da prole e boa qualidade de carcaça.

ESCORE DE CONDIÇÃO CORPORAL EM RUMINANTES

A aferição da condição corporal de ruminantes tem sido recomendada em diversos estudos por refletir o estado metabólico do animal, indicando os indivíduos menos susceptíveis a doenças, mais aptos à reprodução e de melhor rendimento de carcaça. Assim, a avaliação rotineira do escore de condição corporal (ECC) de fêmeas deve contribuir para maior rentabilidade do sistema de produção, pois potenciais problemas podem ser controlados antes que reduzam significativamente a mesma. As metodologias propostas inicialmente para mensurar o ECC foram aprimoradas no decorrer do tempo, tendo em vista o propósito de criação dos ruminantes e as particularidades fenotípicas dos pequenos ruminantes. As pesquisas evidenciam os benefícios proporcionados pela aferição do ECC nas características ligadas à sanidade, reprodução, produção, habilidade materna, consumo alimentar e carcaça de ruminantes. Valores moderados de ECC refletem o equilíbrio metabólico, garantindo melhor desempenho reprodutivo, maior produção de leite, bom desenvolvimento da prole e boa qualidade de carcaça.

Body condition score in ruminants / Escore de condição corporal em ruminantes

The measurement of body condition score in ruminants has been recommended in several studies because this score reflects the metabolic status of the animal, indicating individuals that are less susceptible to diseases, those more able to reproduce and the ones with better carcass yield. Thus, the routine assessment of body condition score (BCS) of females should contribute to increase the profitability of the production system, since potential problems can be controlled before they significantly reduce profitability. The methodologies proposed initially to measure BCS were improved over time, according to the economic purpose of raising ruminant species and the phenotypic particularities of small ruminants. The researches show the benefits provided by the measurement of BCS on the traits related to health, reproduction, production, maternal ability, carcass and feed consumption of ruminants. Moderate values of BCS reflect a metabolic balance, resulting in better reproductive performance, increased milk production, good development of the offspring and good carcass quality.(AU)

A aferição da condição corporal de ruminantes tem sido recomendada em diversos estudos por refletir o estado metabólico do animal, indicando os indivíduos menos susceptíveis a doenças, mais aptos à reprodução e de melhor rendimento de carcaça. Assim, a avaliação rotineira do escore de condição corporal (ECC) de fêmeas deve contribuir para maior rentabilidade do sistema de produção, pois potenciais problemas podem ser controlados antes que reduzam significativamente a mesma. As metodologias propostas inicialmente para mensurar o ECC foram aprimoradas no decorrer do tempo, tendo em vista o propósito de criação dos ruminantes e as particularidades fenotípicas dos pequenos ruminantes. As pesquisas evidenciam os benefícios proporcionados pela aferição do ECC nas características ligadas à sanidade, reprodução, produção, habilidade materna, consumo alimentar e carcaça de ruminantes. Valores moderados de ECC refletem o equilíbrio metabólico, garantindo melhor desempenho reprodutivo, maior produção de leite, bom desenvolvimento da prole e boa qualidade de carcaça.(AU)

Body condition score of Nellore beef cows: a heritable measure to improve the selection of reproductive and maternal traits.

Despite the economic importance of beef cattle production in Brazil, female reproductive performance, which is strongly associated with production efficiency, is not included in the selection index of most breeding programmes due to low heritability and difficulty in measure. The body condition score (BCS) could be used as an indicator of these traits. However, so far little is known about the feasibility of using BCS as a selection tool for reproductive performance in beef cattle. In this study, we investigated the sources of variation in the BCS of Nellore beef cows, quantified its association with reproductive and maternal traits and estimated its heritability. BCS was analysed using a logistic model that included the following effects: contemporary group at weaning, cow weight and hip height, calving order, reconception together with the weight and scores of conformation and early finishing assigned to calves at weaning. In the genetic analysis, variance components of BCS were estimated through Bayesian inference by fitting an animal model that also included the aforementioned effects. The results showed that BCS was significantly associated with all of the reproductive and maternal variables analysed. The estimated posterior mean of heritability of BCS was 0.24 (highest posterior density interval at 95%: 0.093 to 0.385), indicating an involvement of additive gene action in its determination. The present findings show that BCS can be used as a selection criterion for Nellore females.

Genetic relationship among reproductive traits in Nellore cattle.

In order to achieve improvements in production efficiency in livestock, herds of high sexual precocity and good fertility are needed. These traits increase the availability of animals in herd, either for sale or selection, allowing both greater selective intensity and greater genetic progress. This study aimed at estimating genetic parameters for reproductive traits measured directly in females in order to verify whether they could be used as selection criteria for genetic improvement in Nellore cows, as well as estimating the genetic relationship among these traits and scrotal circumference (SC), the traditional selection criterion for sexual precocity in cattle. In addition to SC, stayability (STAY), number of calvings at 53 months (NC53) and heifers rebreeding (HR) were studied. The (co)variances and genetic parameters were estimated using Bayesian inference. STAY, NC53 and HR were analyzed assuming a threshold model, whereas SC was analyzed with a linear model. Heritability estimated for NC53 was 0.22, and this trait was strongly and positively correlated with STAY, meaning selection for NC53 would improve productive longevity of Nellore cows. Correlations estimated between HR and STAY (≈0.97) and between HR and NC53 (≈0.99) allow an improvement on HR rates if selection was applied to traits related to longevity. Genetic correlations among SC and female reproductive traits were positive but weak, suggesting the need to use reproductive traits directly measured in females in order to obtain greater improvements in sexual precocity and longevity.

Genetic analysis of the temperament of Nellore cattle using linear and threshold models.

Temperament is an important trait for the management and welfare of animals and for reducing accidents involving people who work with cattle. The present study aimed to estimate the genetic parameters related to the temperament score (T) and weaning weight (WW) of Nellore cattle, reared in a beef cattle breeding program in Brazil. Data were analyzed using two different two-trait statistical models, both considering WW and T: (1) a linear-linear model in which variance components (VCs) were estimated using restricted maximum likelihood; and (2) a linear-threshold model in which VCs were estimated via Bayesian inference. WW was included in the analyses of T to minimize any possible effects of sequential selection and to allow for estimation of the genetic correlation between these two traits. The heritability estimates for T were 0.21 ± 0.003 (model 1) and 0.26 (model 2, with a 95% credibility interval (95% CI) of 0.21 to 0.32). The estimated genetic correlations between WW and T were of a moderate magnitude (-0.33 ± 0.01 (model 1) and -0.34 (95% CI: -0.40, -0.28, model 2). The genetic correlations between the estimated breeding values (EBVs) obtained for the animals based on the two models were high (>0.92). The use of different models had little influence on the classification of animals based on EBVs or the accuracy of the EBVs.

Genetic parameter estimates and principal component analysis of breeding values of reproduction and growth traits in female Canchim cattle.

Phenotypic data from female Canchim beef cattle were used to obtain estimates of genetic parameters for reproduction and growth traits using a linear animal mixed model. In addition, relationships among animal estimated breeding values (EBVs) for these traits were explored using principal component analysis. The traits studied in female Canchim cattle were age at first calving (AFC), age at second calving (ASC), calving interval (CI), and bodyweight at 420 days of age (BW420). The heritability estimates for AFC, ASC, CI and BW420 were 0.03±0.01, 0.07±0.01, 0.06±0.02, and 0.24±0.02, respectively. The genetic correlations for AFC with ASC, AFC with CI, AFC with BW420, ASC with CI, ASC with BW420, and CI with BW420 were 0.87±0.07, 0.23±0.02, -0.15±0.01, 0.67±0.13, -0.07±0.13, and 0.02±0.14, respectively. Standardised EBVs for AFC, ASC and CI exhibited a high association with the first principal component, whereas the standardised EBV for BW420 was closely associated with the second principal component. The heritability estimates for AFC, ASC and CI suggest that these traits would respond slowly to selection. However, selection response could be enhanced by constructing selection indices based on the principal components.

Genetic parameters for an alternative criterion to improve productive longevity of Nellore cows.

Number of calvings at 53 mo (NC53) was proposed as an alternative selection criterion to improve productive longevity of Nellore cows. This study was carried out to estimate variance components for NC53 by assuming different models, so that the potential for using this selection criterion to improve fertility of Nellore cows could be assessed. Genetic correlations between NC53, number of calvings at 89 mo (NC89), and 2 selection indexes used in this breed were also estimated. The NC53 trait is moderately heritable (posterior mean heritability ≈ 0.17) and selecting for this criterion could improve productive longevity of Nellore cows. Greater response to selection is expected by fitting a threshold animal model for this trait, rather than a linear animal model. Greater accuracy of prediction for this criterion could be achieved by fitting a threshold-linear model, considering this trait and a selection index composed by traits evaluated at weaning and long-yearling.

Genetic parameters and environmental effects on temperament score and reproductive traits of Nellore cattle.

Animal temperament is a trait of economic relevance and its use as a selection criterion requires the identification of environmental factors that influence this trait, as well as the estimation of its genetic variability and interrelationship with other traits. The objectives of this study were to evaluate the effect of the covariates dam age at calving (ADC), long yearling age (YA) and long yearling weight (YW) on temperament score (T) and to estimate genetic parameters for T, scrotal circumference (SC) at long YA and age at first calving (AFC) in Nellore cattle participating in a selection program. The traits were analyzed by the restricted maximum likelihood method under a multiple-trait animal model. For all traits, contemporary group was included as a fixed effect and additive genetic and residual as random effects. In addition to these effects, YA, YW and ADC were considered for analyzing T. In the case of SC and AFC, the effect of long YW was included as a covariate. Genetic parameters were estimated for and between traits. The three covariates significantly influenced T. The heritability estimates for T, SC and AFC were 0.18 ± 0.02, 0.53 ± 0.04 and 0.23 ± 0.08, respectively. The genetic correlations between T and SC, and T and AFC were -0.07 ± 0.17 and -0.06 ± 0.19, respectively. The genetic correlation estimated between SC and AFC was -0.57 ± 0.16. In conclusion, a response to selection for T, SC and AFC is expected and selection for T does not imply correlated responses with the other traits.

Suplementação da dieta de codornas com minerais nas formas orgânicas sobre o desempenho e a qualidade dos ovos / Supplementation in quail diet with organic minerals on performance and egg quality

Foram realizados três experimentos com o objetivo de avaliar o efeito da suplementação de minerais na forma orgânica na dieta de codornas japonesas na fase de postura sobre o desempenho e a qualidade de ovos das aves. Os níveis de minerais utilizados por kg de ração, para cada experimento, foram: controle, 0,35, 0,70 e 1,05mg de Se orgânico (experimento 1); controle, 50, 100 e 150mg de Zn orgânico (experimento 2) e controle, 60, 120 e 180mg de Mn orgânico (experimento 3). As aves foram distribuídas em delineamento inteiramente ao acaso, sendo oito aves por parcela e seis repetições por tratamento. Foram avaliadas as características de desempenho - consumo diário de ração, peso dos ovos, porcentagem de postura, conversão alimentar por massa de ovos e por dúzia de ovos e viabilidade - e qualidade dos ovos - unidade Haugh, índice gema, porcentagens de casca, albúmen e gema, espessura de casca e gravidade específica. O Zn orgânico suplementado à dieta melhorou o desempenho das aves e a qualidade dos ovos, o Mn orgânico melhorou a qualidade da casca e reduziu o peso dos ovos e o Se não apresentou efeitos sobre as características avaliadas.(AU)

Three experiments were carried out to evaluate the effect of minerals in organic form in diet supplementation in Japanese quails performance. The levels of minerals used per kg of diet for each experiment were: Experiment 1: control, 0.35; 0.70 and 1.05mg organic; Experiment 2: control, 50; 100 and 150mg organic Zn; and Experiment 3: control, 60; 120 and 180mg organic Mn. The birds were randomly allotted in treatments with eight birds per experimental unit and six replicates per treatment. Performance traits of the quails estimated by daily feed intake, egg weight, egg production, feed conversion by egg mass and per dozen eggs and viability, and egg quality measured by Haugh unit, yolk index, shell, albumen and yolk percentage, shell thickness and specific gravity were evaluated. The organic Zn diet supplementation improved bird performance and egg quality, the organic Mn diet improved eggshell quality and reduced egg weight, and the Se diet did not affect the evaluated characteristics.(AU)

Suplementação da dieta de codornas com minerais nas formas orgânicas sobre o desempenho e a qualidade dos ovos / Supplementation in quail diet with organic minerals on performance and egg quality

Foram realizados três experimentos com o objetivo de avaliar o efeito da suplementação de minerais na forma orgânica na dieta de codornas japonesas na fase de postura sobre o desempenho e a qualidade de ovos das aves. Os níveis de minerais utilizados por kg de ração, para cada experimento, foram: controle, 0,35, 0,70 e 1,05mg de Se orgânico (experimento 1); controle, 50, 100 e 150mg de Zn orgânico (experimento 2) e controle, 60, 120 e 180mg de Mn orgânico (experimento 3). As aves foram distribuídas em delineamento inteiramente ao acaso, sendo oito aves por parcela e seis repetições por tratamento. Foram avaliadas as características de desempenho - consumo diário de ração, peso dos ovos, porcentagem de postura, conversão alimentar por massa de ovos e por dúzia de ovos e viabilidade - e qualidade dos ovos - unidade Haugh, índice gema, porcentagens de casca, albúmen e gema, espessura de casca e gravidade específica. O Zn orgânico suplementado à dieta melhorou o desempenho das aves e a qualidade dos ovos, o Mn orgânico melhorou a qualidade da casca e reduziu o peso dos ovos e o Se não apresentou efeitos sobre as características avaliadas.

Three experiments were carried out to evaluate the effect of minerals in organic form in diet supplementation in Japanese quails performance. The levels of minerals used per kg of diet for each experiment were: Experiment 1: control, 0.35; 0.70 and 1.05mg organic; Experiment 2: control, 50; 100 and 150mg organic Zn; and Experiment 3: control, 60; 120 and 180mg organic Mn. The birds were randomly allotted in treatments with eight birds per experimental unit and six replicates per treatment. Performance traits of the quails estimated by daily feed intake, egg weight, egg production, feed conversion by egg mass and per dozen eggs and viability, and egg quality measured by Haugh unit, yolk index, shell, albumen and yolk percentage, shell thickness and specific gravity were evaluated. The organic Zn diet supplementation improved bird performance and egg quality, the organic Mn diet improved eggshell quality and reduced egg weight, and the Se diet did not affect the evaluated characteristics.

Genetic and environmental effects on age at first farrowing in sows in southeastern Brazil.

We evaluated genetic and environmental factors affecting age at first farrowing of sows in the Brazilian southeast. For this purpose, 466 observations regarding the age at first farrowing were made for Dalland-C40© animals belonging to two herds. The effects of the environmental factors on this trait were assessed by means of a model that included, as random effects, the influence of the sow's father and mother and, as fixed effects, the influence the year of birth, the herd and the birth season, along with the covariable litter size at birth. The variance components were estimated using the derivative-free restricted maximum likelihood method. The estimated mean was 354.8 ± 25.87 days, with a coefficient of variation of 7.29%. Significant effects on the trait were observed for the herd, the year and the season of birth; but a linear effect of litter size at birth on the age at first farrowing was not observed. The boar did not significantly contribute to the variation occurring among the sows, whereas the sow's mother caused significant variation. The heritability estimate for the age at first farrowing was 0.44 ± 0.15, which is considered high. We concluded that herd effect and year and season of birth should be taken into consideration for an accurate genetic comparison; consequently, the animals should be joined into contemporary groups.

Estimates of genetic parameters for visual scores and daily weight gain in Brangus animals.

(Co)variance components were estimated for visual scores of conformation (CY), early finishing (PY) and muscling (MY) at 550 days of age (yearling), average daily gain from weaning to yearling (GWY), conformation (CW), early finishing (PW) and muscling (MW) scores at weaning, and average daily gain from birth to weaning (GBW) in animals forming the Brazilian Brangus breed born between 1986 and 2002 from the livestock files of GenSys Consultants Associados S/C Ltda. The data set contained 53 683; 45 136; 52 937; 56 471; 24 531; 21 166; 24 006 and 25 419 records for CW, PW, MW, GBW, CY, PY, MY and GWY, respectively. Data were analyzed by the restricted maximum likelihood method using single- and two-trait animal models. Direct heritability estimates obtained by single-trait analysis were 0.12, 0.14, 0.13 and 0.14 for CY, PY and MY scores and GWY, respectively. A positive association was observed between the same visual scores at weaning and yearling, with correlations ranging from 0.64 to 0.94. Estimated correlations between GBW and weaning and yearling scores ranged from 0.60 to 0.77. The genetic correlation between GBW and GWY was low (0.10), whereas correlations of 0.55, 0.37 and 0.47 were observed between GWY and CY, PY and MY, respectively. Moreover, GWY showed a weak correlation with CW (0.10), PW (-0.08) and MW (-0.03) scores. These results indicate that selection of the traits that was studied would result in a small response. In addition, selection based on average daily gain may have an indirect effect on visual scores as the correlations between GWY and visual scores were generally strong.

Quantitative genetic study on growth traits of Brahman cattle in Brazil / Estudo genético quantitativo de características de crescimento de bovinos da raça Brahman no Brasil

This research aimed at estimating genetic parameters for birth weight (BW), weight at 120 days (W120), weaning weight (W210), yearling weight (W365), weight at 455 days (W455) and weight at 550 days (W550) and direct and indirect efficiencies for selection based on these traits for Brahman cattle in Brazil. We analyzed 15,664; 7,432; 6,585; 4,223; 3,362 and 2,517 records on BW, W120, W210, W365, W455 and W550, respectively, from animals enrolled in the Genetic Breeding Program of Brahman Breed (PMGRB) under management of the National Association of Breeders and Researchers (ANCP). Heritability and variance components were estimated by restricted maximum likelihood using bi-trait models. The models considered the effects of contemporary groups as fixed and age of dam, at calving as covariate (linear and quadratic) and the genetic direct animal effect and permanent environment of the cow effect as random. The genetic maternal effect was also included for BW, W120 and W210. Estimates of direct heritability ranged from 0.28 to 0.41 for BW, from 0.36 to 0.52 for W120, from 0.36 to 0.46 for W210, from 0.40 to 0.41 for W365, from 0.33 to 0.35 for W455 and from 0.28 to 0.36 for W550. Genetic correlations between BW and the other weights ranged from 0.51 to 0.79, between W120 and subsequent weights from 0.78 to 0.93, between W210 and subsequent weight from 0.98 to 0.99, while the estimates between W365 to W455 and W550 were 0.99 and 0.98, respectively, and between W455 and W550, 0.98. The results showed all traits could be used as selection criteria. The genetic correlation indicated that selection applied to any trait would bring change in the others. Weaning weight (W210) is the more appropriate trait for selection criterion for the Brahman breed.

Os objetivos foram estimar parâmetros genéticos para os pesos ao nascer (PN), aos 120 (P120), 210 (P210), 365 (P365), 455 (P4555) e 550 (P550) dias de idade e eficiências relativas de seleção indireta versus direta entre as referidas características, para bovinos da raça Brahman, no Brasil. Foram analisados 15.664, 7.432, 6.585, 4.223, 3.362 e 2.517 dados de PN, P120, P210, P365, P455 e P550, respectivamente. Os componentes de variância e as herdabilidades foram estimados pelo método de máxima verossimilhança restrita, em modelos bicaracterísticas. Foram considerados como efeitos fixos grupos de contemporâneos e idade da vaca ao parto como covariável (efeitos linear e quadrático) e, como aleatórios, o efeito de animal e de ambiente permanente da vaca. Para PN, P120 e P210 considerou-se ainda o efeito aleatório genético materno. As estimativas de herdabilidade direta variaram de 0,28 a 0,41 para PN, de 0,36 a 0,52 para P120, de 0,36 a 0,46 para P210, de 0,40 a 0,41 para P365, de 0,33 a 0,35 para P455 e de 0,28 a 0,36 para P550. As correlações genéticas entre PN e os demais pesos variaram de 0,51 a 0,79, entre P120 e os pesos subsequentes, de 0,78 a 0,93, entre P210 e os pesos subsequentes, de 0,98 a 0,99, enquanto que entre P365 com P455 e P550, foram 0,99 e 0,98, respectivamente, e entre P455 e P550, 0,98. As caracteristicas estudadas podem ser usadas como critério de seleção e as correlações genéticas estimadas indicaram que, ao se selecionar os animais para qualquer uma das características, automaticamente promoverá também respostas nas demais. O P210 em termos de eficiência relativa de seleção indireta seria o mais indicado como critério de seleção, com a ressalva de que esse peso não apresentou efeito materno importante.

QUANTITATIVE GENETIC STUDY ON GROWTH TRAITS OF BRAHMAN CATTLE IN BRAZIL / Estudo genético quantitativo de características de crescimento de bovinos da raça Brahman no Brasil.

Os objetivos foram estimar parâmetros genéticos para os pesos ao nascer (PN), aos 120 (P120), 210 (P210), 365 (P365), 455 (P4555) e 550 (P550) dias de idade e eficiências relativas de seleção indireta versus direta entre as referidas características, para bovinos da raça Brahman, no Brasil. Foram analisados 15.664, 7.432, 6.585, 4.223, 3.362 e 2.517 dados de PN, P120, P210, P365, P455 e P550, respectivamente. Os componentes de variância e as herdabilidades foram estimados pelo método de máxima verossimilhança restrita, em modelos bicaracterísticas. Foram considerados como efeitos fixos grupos de contemporâneos e idade da vaca ao parto como covariável (efeitos linear e quadrático) e, como aleatórios, o efeito de animal e de ambiente permanente da vaca. Para PN, P120 e P210 considerou-se ainda o efeito aleatório genético materno. As estimativas de herdabilidade direta variaram de 0,28 a 0,41 para PN, de 0,36 a 0,52 para P120, de 0,36 a 0,46 para P210, de 0,40 a 0,41 para P365, de 0,33 a 0,35 para P455 e de 0,28 a 0,36 para P550. As correlações genéticas entre PN e os demais pesos variaram de 0,51 a 0,79, entre P120 e os pesos subseqüentes, de 0,78 a 0,93, entre P210 e os pesos subseqüentes, de 0,98 a 0,99, enquanto que entre P365 com P455 e P550, foram 0,99 e 0,98, respectivamente, e entre P455 e P550, 0,98. As caracteristicas estudadas podem ser usadas como critério de seleção e