Heritability Estimates For Birth Weight Research Articles

(Co)variance components and genetic parameters for growth traits in Arabi sheep using different animal models

The objective of the present study was to estimate genetic parameters for body weight at different ages in Arabi sheep using data collected from 1999 to 2009. Investigated traits consisted of birth weight (N = 2776), weaning weight (N = 2002) and weight at six months of age (N = 1885). The data were analyzed using restricted maximum likelihood analysis, by fitting univariate and multivariate animal models. All three weight traits were significantly influenced by birth year, sex and birth type. Age of dam only significantly affected birth weight. Log-likelihood ratio tests were conducted to determine the most suitable model for each growth trait in univariate analyses. Direct and total heritability estimates for birth weight, weaning weight and weight at six months of age (based on the best model) were 0.42 and 0.16 (model 4), 0.38 and 0.13 (model 4) and 0.14 and 0.14 (model 1), respectively. Estimation of maternal heritability for birth weight and weaning weight was 0.22 and 0.18, respectively. Genetic and phenotypic correlations among these traits were positive. Phenotypic correlations among traits were low to moderate. Genetic correlations among traits were positive and higher than the corresponding phenotypic correlations. Weaning weight had a strong and significant correlation with weight at six months of age (0.99). We conclude that selection can be made in animals based on weaning weight instead of the present practice of selection based on weight at six months.

Genetic parameters and relationships between growth traits and scrotal circumference measured at different ages in Nellore cattle

Records from 106,212 Nellore animals, born between 1998 and 2006, were used to estimate (co)variance components and genetic parameters for birth weight (BW), average weight gains from birth to weaning (GBW), average weight gains from weaning to after yearling (GWAY), weaning hip height (WHH), postweaning hip height (PHH) and scrotal circumferences at 9 (SC9), 12 (SC12) and 15 (SC15) months of age. (Co)variance components were estimated by an animal model using multi-trait analysis. Heritability estimates for BW, GBW, GWAY, WHH, PHH, SC9, SC12 and SC15 were 0.31 ± 0.01; 0.25 ± 0.02; 0.30 ± 0.04; 0.51 ± 0.04; 0.54 ± 0.04; 0.39 ± 0.01; 0.41 ± 0.01 and 0.44 ± 0.02, respectively. Genetic correlations between growth traits ranged from 0.09 ± 0.01 to 0.88 ± 0.01, thereby implying that, at any age, selection to increase average weight gains will also increase stature. Genetic correlations between BW and average weight gains with scrotal circumferences were all positive and moderate (0.15 ± 0.03 to 0.38 ± 0.01). On the other hand, positive and low genetic associations were estimated between hip height and scrotal circumference at different ages (0.09 ± 0.01 to 0.17 ± 0.02). The results of this study pointed out that selection to larger scrotal circumferences in males will promote changes in average weight gains. In order to obtain Nellore cattle with the stature and size suitable for the production system, both weight gain and hip height should be included in a selection index.

Efeitos genéticos aditivos e não-aditivos em características de crescimento, reprodutivas e habilidade materna em ovinos das raças Santa Inês, Somalis Brasileira, Dorper e Poll Dorset

Efeitos genético aditivo, de dominância e de recombinação em cruzamentos entre as raças Santa Inês (SI), Somalis Brasileira (So), Dorper (Do) e Poll Dorset (Po) foram estimados para as características de crescimento, reprodutivas e de habilidade materna. Os dados foram obtidos da Gaasa e Alimentos LTDA, uma empresa que participa do Programa de Melhoramento Genético de Caprinos e Ovinos (GENECOC) da Embrapa Caprinos. Inicialmente, 3.573 registros foram analisados por meio do procedimento MIXED do pacote estatístico SAS (1999). As análises foram realizadas considerando os efeitos da diferença genética aditiva entre as raças, de dominância e de recombinação. O peso ao nascer foi influenciado pelos efeitos genéticos aditivos, enquanto o peso ao desmame e o ganho de peso pré-desmame foram influenciados por efeitos genéticos não-aditivos. A estimativa de herdabilidade direta para o peso ao nascer foi moderada, o que indica a existência de variabilidade genética passível de ser explorada por meio da seleção individual. Do mesmo modo, as estimativas de herdabilidade das características idade ao primeiro parto e peso total das crias ao nascer indicaram a existência de variabilidade genética para obter ganhos genéticos por meio da seleção. Os genes das raças Poll Dorset e Dorper tiveram papel importante para melhor desempenho ponderal, portanto, essas raças podem ser indicadas como paternas no cruzamento terminal. A utilização de matrizes F1 Santa Inês x Somalis Brasileira em cruzamentos com reprodutores Poll Dorset pode levar a maior eficiência reprodutiva.

Estimates of (co)variance components and genetic parameters for growth traits in Sirohi goat

Data were collected over a period of 21years (1988-2008) to estimate (co)variance components for birth weight (BWT), weaning weight (WWT), 6-month weight (6WT), 9-month weight (9WT), 12-month weight (12WT), average daily gain from birth to weaning (ADG1), weaning to 6WT (ADG2), and from 6WT to 12WT (ADG3) in Sirohi goats maintained at the Central Sheep and Wool Research Institute, Avikanagar, Rajasthan, India. Analyses were carried out by restricted maximum likelihood, fitting six animal models with various combinations of direct and maternal effects. The best model was chosen after testing the improvement of the log-likelihood values. Heritability estimates for BWT, WWT, 6WT, 9WT, 12WT, ADG1, ADG2, and ADG3 were 0.39 ± 0.05, 0.09 ± 0.03, 0.06 ± 0.02, 0.09 ± 0.03, 0.11 ± 0.03, 0.10 ± 0.3, 0.04 ± 0.02, and 0.01 ± 0.01, respectively. For BWT and ADG1, only direct effects were significant. Estimate of maternal permanent environmental effect were important for body weights from weaning to 12WT and also for ADG2 and ADG3. However, direct maternal effects were not significant throughout. Estimate of c (2) were 0.06 ± 0.02, 0.03 ± 0.02, 0.06 ± 0.02, 0.05 ± 0.02, 0.02 ± 0.02, and 0.02 ± 0.02 for 3WT, 6WT, 9WT, 12WT, ADG2, and ADG3, respectively. The estimated repeatabilities across years of ewe effects on kid body weights were 0.10, 0.08, 0.05, 0.08, and 0.08 at birth, weaning, 6, 9, and 12months of age, respectively. Results suggest possibility of modest rate of genetic progress for body weight traits and ADG1 through selection, whereas only slow progress will be possible for post-weaning gain. Genetic and phenotypic correlations between body weight traits were high and positive. High genetic correlation between 6WT and 9WT suggests that selection of animals at 6months can be carried out instead of present practice of selection at 9months.

Eficiência reprodutiva e influência de fatores de meio e de herança sobre a variação no peso ao nascer de bubalinos no estado de Rondônia

Avaliaram-se as características reprodutivas e o peso ao nascer em bubalinos mestiços e determinaram-se os possíveis fatores de sua variação. Utilizaram-se 115 informações de idade ao primeiro parto e 420 intervalos de parto referentes a 127 fêmeas 1/2, 3/4, 7/8, 15/16 Murrah × Mediterrâneo e puras por cruza (PC). Também foram utilizados 557 pesos ao nascer de progênies resultantes do cruzamento entre essas fêmeas e cinco touros da raça Murrah. Os nascimentos ocorreram no período de 1979 a 2001. A idade ao primeiro parto (1291 ± 235 dias) foi influenciada pelo grupo de contemporâneos da búfala. O intervalo de partos (451 ± 139 dias) foi afetado pelos efeitos fixos grupo de contemporâneos da búfala; peso da búfala no pós-parto anterior; idade da búfala ao parto anterior, linear e quadrática; bem como, pelo efeito aleatório de búfala. O grupo genético não determinou variações sobre as características idade ao primeiro parto e intervalo de partos. O peso ao nascer (34,25 ± 5,02 kg) foi influenciado pelo sexo da cria, pelo grupo de contemporâneos do bezerro e pelo peso da búfala após o parto, além do efeito aleatório de mãe. O grupo genético da búfala, a idade da búfala ao parto e o pai da cria não influenciaram o peso ao nascer. A herdabilidade estimada do peso ao nascimento foi de 0,60 ± 0,12. Os fatores que apresentaram diferenças significativas devem ser considerados na avaliação das características reprodutivas e do peso ao nascer.

Modeling Genetic and Environmental Factors to Increase Heritability and Ease the Identification of Candidate Genes for Birth Weight: A Twin Study

Heritability estimates of birth weight have been inconsistent. Possible explanations are heritability changes during gestational age or the influence of covariates (e.g. chorionicity). The aim of this study was to model birth weights of twins across gestational age and to quantify the genetic and environmental components. We intended to reduce the common environmental variance to increase heritability and thereby the chance of identifying candidate genes influencing the genetic variance of birth weight. Perinatal data were obtained from 4232 live-born twin pairs from the East Flanders Prospective Twin Survey, Belgium. Heritability of birth weights across gestational ages was estimated using a non-linear multivariate Gaussian regression with covariates in the means model and in covariance structure. Maternal, twin-specific, and placental factors were considered as covariates. Heritability of birth weight decreased during gestation from 25 to 42 weeks. However, adjusting for covariates increased the heritability over this time period, with the highest heritability for first-born twins of multipara with separate placentas, who were staying alive (from 52% at 25 weeks to 30% at 42 weeks). Twin-specific factors revealed latent genetic components, whereas placental factors explained common and unique environmental factors. The number of placentas and site of the insertion of the umbilical cord masked the effect of chorionicity. Modeling genetic and environmental factors leads to a better estimate of their role in growth during gestation. For birth weight, mainly environmental factors were explained, resulting in an increase of the heritability and thereby the chance of finding genes influencing birth weight in linkage and association studies.

Genetic parameter estimates of pre-weaning growth traits in Kermani sheep

Genetic and phenotypic parameters were estimated on 2332 lambs from 61 sires and 815 dams for birth weight (BW), and on 2182 lambs from 54 sires and 760 dams for average daily gain (ADG), weaning weight (WW) and Kleiber ratio (KR). The data was collected from 1993 to 2004 at Breeding Station of Kermani sheep. (Co) variance components and corresponding genetic parameters were obtained with univariate and multivariate analyses fitting animal models using restricted maximum likelihood (REML) methods. The most suitable model for each trait was determined based on log likelihood ratio tests. Lamb gender, type of birth, age of dam and year of birth were significant sources of variation on BW, ADG, WW and KR ( P < 0.01). Direct estimates of heritability for BW, ADG, WW and KR were 0.04, 0.15, 0.27 and 0.08, respectively. The estimate of maternal heritability for BW was 0.24. The estimates of maternal permanent environmental variance as a proportion of phenotypic variance were 0.13 and 0.13 for ADG and WW, respectively. The estimates of the direct genetic correlation between BW-ADG, BW-WW, BW-KR, ADG-WW, ADG-KR and WW-KR were 0.71, 0.68, 0.59, 0.86, 0.76 and 0.89, respectively. The common environmental correlations estimate between ADG-WW was 0.46 and genetic correlation between maternal effects of BW with direct effects of ADG, WW and KR were low and ranged from 0.02 to 0.03. The estimates of the phenotypic and environmental correlation between traits were positive and ranged from 0.21 to 0.94 and 0.02 to 0.95, respectively.

Variance components and heritabilities for body weight traits in Sangsari sheep, using univariate and multivariate animal models

The records of growth traits of 2778 lambs of Sangsari sheep flock from Damghan research station (Semnan Province, Iran), collected during 1986–1998, were analyzed to estimate the variance components and heritabilities of some growth and gain traits, using a Derivative Free, Restricted Maximum Likelihood (DFREML) approach. The single and/or multiple trait animal models were employed to perform the mentioned task. Different models of DFREML run for univariate analysis and log likelihood ratio for different models were compared to locate the most appropriate model for the analysis of each trait. With univariate analysis, direct heritability estimates for birth weight, weaning weight, 6 months weight, 9 months weight, yearling weight, average daily gain from birth to weaning, average daily gain from birth to 6 months of age and average daily gain from weaning to 6 months of age were 0.33 ± 0.05, 0.17 ± 0.05, 0.49 ± 0.07, 0.08 ± 0.05, 0.10 ± 0.05, 0.03 ± 0.02, 0.17 ± 0.60 and 0.05 ± 0.30, respectively. Maternal heritability estimates were 0.65 for birth weight, 0.08 for weaning weight, 0.01 for average daily gain from birth to weaning and 0.11 for 6 months weight. The results of pair-wise and multivariate (five traits) analyses for heritability estimates are also reported, which are not very different from those mentioned above. The results of this study showed that maternal heritability was higher for pre-weaning than for post-weaning traits.

Seleção para peso pós-desmama em um rebanho Gir. 2. Estimativas de variâncias e parâmetros genéticos dos efeitos direto e materno para características de crescimento

Componentes de variância e parâmetros genéticos para características de crescimento foram estimados usando diferentes modelos em um rebanho da raça Gir. Utilizou-se o método da máxima verossimilhança restrita sob modelo animal univariado. Os modelos de análise incluíram os efeitos fixos de mês de nascimento, grupo contemporâneo e idade da vaca. Cinco modelos diferindo quanto aos efeitos aleatórios foram testados. Para todas as características da fase pré-desmama, o teste de razão de verossimilhança (LRT) indicou o modelo com efeito genético aditivo direto e efeitos maternos (genético e de ambiente permanente) como o de melhor ajuste. As estimativas de herdabilidade direta para peso ao nascer (PN), peso aos quatro meses corrigido para 120 dias (P120), peso à desmama corrigido para 210 dias (P210) e ganho diário na fase pré-desmama (GPRE) foram, respectivamente, 0,31± 0,07; 0,14 ± 0,06; 0,23 ± 0,07 e 0,22 ± 0,07. Para as características da fase pós-desmama, o modelo que forneceu o melhor ajuste aos dados incluiu apenas o efeito genético aditivo direto. As estimativas de herdabilidade direta para peso de machos ao final da prova de ganho de peso (P378), peso de fêmeas corrigido para 550 dias (P550), ganho diário na prova de ganho de peso (G112), altura aos 378 dias em machos (AM) e altura aos 550 dias, em fêmeas (AF) foram, respectivamente: 0,45 ± 0,11; 0,29 ± 0,11; 0,37 ± 0,11; 0,79 ± 0,13 e 0,36 ± 0,0. Os efeitos maternos, tanto o genético quanto o de ambiente permanente, foram fontes de variação importantes para as características da fase pré-desmama, não sendo verificada influência desses efeitos sobre as características da fase pós-desmama.

한우 암소의 성장곡선 모수에 대한 유전적 경향

The objective of this study was to estimate genetic variances of growth curve parameters in Hanwoo cows. The data used in this study were records from 1,083 Hanwoo cows raised at Hanwoo Experiment Station, National Livestock Research Institute (NLRI). First evaluation model (Model I) fit year-season of birth and age of dam as fixed effects and second model (Model II) added age at the final weight as a linear covariate to Model I. Heritability estimates of A, b and k from Gompertz model were 0.22, 0.11 and 0.07 using model and 0.28, 0.11 and 0.12 using model . Those from Von Bertalanffy model were 0.22, 0.11 and 0.07 using model , 0.28, 0.11 and 0.12 using model . Heritability estimates of A, b and k from Logistic model were 0.14, 0.07 and 0.05 using model , 0.18, 0.07 and 0.12 using model . Heritability estimates of A from Gompertz model were higher than those from Von Bertalanffy model or Logistic model in both model and model . Heritability estimates of b from Logistic model were higher than those from Gompertz model or Von Bertalanffy model in both model and model . Heritability estimates of birth weight, weaning weight, 3 month weight, 6 month weight, 9 month weight, 12 month weight, 18 month weight, 24 month weight, 36 month weight were after linear age adjustment 0.27, 0.11, 0.19, 0.14, 0.16, 0.23, 0.52 and 0.32, respectively. Heritability estimates of birth weight, weaning weight, 3 month weight, 6 month weight, 9 month weight and 24 month weight fit by Gompertz model were larger than those estimated from linearly adjusted data. Heritability estimates of 12 month weight, 18 month weight and 36 month weight fit by Von Bertalanffy model were larger than those estimated from linearly adjusted data. In the multitrait analyses for parameters from Gompertz model, genetic and phenotypic correlations between A and k parameters were 0.47 and 0.67 using model and 0.56 and 0.63 using model . Those between the A and b parameters were 0.69 and 0.34 using model and 0.72 and 0.37 using model . Those between the b and k parameters were 0.26 and 0.01 using model and 0.30 and 0.01 using model . In the multitrait analyses for parameters from Von Bertalanffy model, genetic and phenotypic correlations between A and k parameters were 0.49 and 0.67 suing model and 0.57 and 0.70 using model . Those between the A and b parameters were 0.61 and 0.33 using model and 0.60 and 0.30 using model . Those between the b and k parameters were 0.20 and 0.02 using model and 0.16 and 0.00 using model . In the multitrait analyses for parameters from Logistic model, genetic and phenotypic correlations between A and k parameters were 0.43 and 0.67 using model and 0.50 and 0.63 using model . Those between the A and b parameters were 0.47 and 0.22 using model and 0.38 and 0.24 using model . Those between the b and k parameters were 0.09 and 0.02 using model and 0.02 and 0.13 using model .

Genetic parameter estimates for scrotal circumference and semen characteristics of Line 1 Hereford bulls1

The objectives of this study were to estimate heritability for scrotal circumference (SC) and semen traits and their genetic correlations (rg) with birth weight (BRW). Semen traits were recorded for Line 1 Hereford bulls (n = 841), born in 1963 or from 1967 to 2000, that were selected for use at Fort Keogh (Miles City, MT) or for sale. Semen was collected by electroejaculation when bulls were a mean age of 446 d. Phenotypes were BRW, SC, ejaculate volume, subjective scores for ejaculate color, swirl, sperm concentration and motility, and percentages of sperm classified as normal and live or having abnormal heads, abnormal midpieces, proximal cytoplasmic droplets (primary abnormalities), bent tails, coiled tails, or distal cytoplasmic droplets (secondary abnormalities). Percentages of primary and secondary also were calculated. Data were analyzed using multiple-trait derivative-free REML. Models included fixed effects for contemporary group, age of dam, age of bull, inbreeding of the bull and his dam, and random animal and residual effects. Random maternal and permanent maternal environmental effects were also included in the model for BRW. Estimates of heritability for BRW, SC, semen color, volume, concentration, swirl, motility, and percentages of normal, live, abnormal heads, abnormal midpieces, proximal cytoplasmic droplets, bent tails, coiled tails, distal cytoplasmic droplets, and primary and secondary abnormalities were 0.34, 0.57, 0.15, 0.09, 0.16, 0.21, 0.22, 0.35, 0.22, 0.00 0.16, 0.37, 0.00 0.34 0.00, 0.30, and 0.33, respectively. Estimates of rg for SC with color, volume, concentration, swirl, motility, and percentages of live, normal, and primary and secondary abnormalities were 0.73, 0.20, 0.77, 0.40, 0.34, 0.63, 0.33, -0.36, and -0.45, respectively. Estimates of rg for BRW with SC, color, volume, concentration, swirl, motility, and percentages live, normal, and primary and secondary abnormalities were 0.28, 0.60, 0.08, 0.58, 0.44, 0.21, 0.34, 0.20, -0.02, and -0.16, respectively. If selection pressure was applied to increase SC, all of the phenotypes evaluated would be expected to improve. Predicted correlated responses in semen characteristics per genetic SD of selection applied to SC were 0.87 genetic SD or less. If selection pressure was applied to reduce BRW, the correlated responses would generally be smaller but antagonistic to improving all of the phenotypes evaluated. Predicted correlated responses in SC and semen characteristics per genetic SD of selection applied to BRW were less than 0.35 genetic SD.

Genetic and phenotypic parameters of body weight in West African Dwarf goat and Djallonké sheep

The International Trypanotolerance Centre's small ruminant breeding programme was initiated in 1995. The aim was to increase the efficiency of meat production and the trypanotolerance of the animals (sheep and goat). To achieve that goal, selection was based on estimated breeding values for daily weight gain from 4 to 12 months of age measured on trypanotolerance challenge. The purpose of this study was to estimate genetic parameters for growth traits and to evaluate genetic trends in West African Dwarf goat and Djallonké sheep resulting from the breeding programme under a low input production environment. Data for West African Dwarf goat and Djallonké sheep included birth weight (BW), weaning weight (W120), yearling weight (W360), pre-weaning (GR0–4) and post-weaning (GR4–12) growth rate. The data were analysed using an animal model that accounted for fixed effects of sex, year of birth, season of birth, parity of the dam, type of birth and the interaction year by season of birth. Estimates of heritability for BW, W120, W360, GR0–4 and GR4–12 were 0.5, 0.43, 0.30, 0.32 and 0.11 for goats and 0.39, 0.54, 0.21, 0.54 and 0.23 for sheep, respectively. The genetic correlation between BW and W120 was high for goats (0.74) and moderate for sheep (0.47). Genetic correlations between W120 and GR4–12 were high (0.92) for goats and moderate (0.49) for sheep. Between GR0–4 and BW the correlation was positive but low for sheep (0.26) and moderate for goats (0.60). Positive trends were found in mean estimated breeding values for animals born in the period 1995–2002 which demonstrated the effectiveness of the implemented breeding programs.

Metanálise bayesiana de parâmetros genéticos para características de crescimento em bovinos de corte

Foi conduzida uma metanálise, sob enfoque bayesiano, em um conjunto de estimativas de herdabilidade, para características de crescimento em bovinos de corte de raças indianas, com 869 estimativas de herdabilidade de efeito direto, 186 estimativas de herdabilidade de efeito materno e 123 estimativas do coeficiente de correlação genética entre os efeitos direto e materno. A construção e o desenvolvimento de um modelo hierárquico possibilitam a obtenção de estimativas combinadas de herdabilidade para as características peso ao nascimento, peso ao desmame, peso aos 365 dias e peso aos 550 dias, cujos valores são, respectivamente: 0,31, 0,24, 0,28 e 0,33 para efeitos diretos; 0,09, 0,13, 0,12 e 0,05 para efeitos maternos; e -0,16, -0,16, -0,20 e -0,16 para as correlações entre esses efeitos. A metanálise conduzida sob enfoque bayesiano mostrou-se bastante adequada, uma vez que um modelo hierárquico considera as variâncias dentro e entre os estudos, e sua implementação e condução são facilitadas em virtude, principalmente, do avanço conseguido na área computacional.

Genetic parameter of birth and weaning weights for Friesian calves by using an animal model

Abstract. Birth and weaning weights of 556 Friesian calves by 41 sires out of 318 different dams over a 11 years period were obtained from a herd of Friesian in Sakha Experimental Farm, Ministry of Agriculture, Egypt were used. The records were analyzed by Multiple Trait Likelihood Method (MTDFREML) by using a repeatability animal model (BOLDMAN et al., 1995). Convergence was attained after 699 iterations. The fixed effects included in the model were season and year of calving, parity and sex and the random effects were direct and maternal genetic, permanent maternal environmental and error. Direct heritability estimates for birth weight (BW) and weaning weight (WW) are 0.28 and 0.13, respectively, while, maternal heritability estimates for the same traits are 0.14 and 0.06, respectively. Repeatability estimates are 0.75 and 0.15 for BW and WW, respectively. Phenotypic and genetic correlations are 0.89 and 0.80, respectively. Estimates of calve breeding values ranged from −3.12 to 4.11 kg for BW and ranged from −4.10 to 5.11 kg for WW. Sire breeding values ranged from −3.40 to 2.99 kg for BW and ranged from −2.50 to 4.47 kg for WW. Dam breeding values ranged from −6.80 to 5.54 kg for BW and ranged from -6.10 to 6.39 kg for WW.

Meta-análise para estimativas de herdabilidade para características de crescimento em bovinos de corte

Um conjunto de estimativas de herdabilidade de características de crescimento em bovinos de corte de raças indianas, procedentes de 186 artigos publicados, foi compilado e sumarizado, utilizando-se técnicas de meta-análise. Com o objetivo de identificar quais fatores afetam as estimativas de herdabilidade ponderadas, empregou-se o método dos mínimos quadrados para análise de um modelo de efeito fixo. Os fatores estatisticamente significativos, para as quatro características, foram raça e método de estimação, sendo que este último deve ser sempre considerado na síntese dessas estimativas. Os valores das estimativas combinadas das herdabilidades, para as características peso ao nascimento, peso à desmama, peso aos 365 dias e peso aos 550 dias obtidos foram: 0,30±0,01; 0,23±0,01; 0,27±0,01; e 0,31±0,01, respectivamente. A meta-análise é uma técnica recomendada para resumir informações sobre parâmetros genéticos de populações bovinas.

Análise de agrupamento para implementação da meta-análise em estimativas de herdabilidade para características de crescimento em bovinos de corte

Estimativas de herdabilidade de características de crescimento são informações muito utilizadas em programas de melhoramento genético de bovinos de corte. Neste trabalho, foram compiladas 869 estimativas de herdabilidade, provenientes de 186 artigos publicados, das características peso ao nascimento, peso à desmama, peso aos 365 dias e peso aos 550 dias, de bovinos de corte de origem indiana. As estimativas foram divididas em grupos, em cada uma das quatro características, utilizando-se o método de agrupamento de Ward, e combinadas, dentro de cada grupo, por intermédio da meta-análise. Observou-se, para todas as características, que os grupos compostos por animais da raça Nelore presentes, em sua maioria, no Brasil, apresentaram maiores estimativas combinadas de herdabilidade que os demais grupos. Foram utilizados dois métodos, o da máxima verossimilhança restrita e o proposto por DerSimonian e Laird, para estimar a variância entre os estudos, tendo o primeiro apresentado valores superiores.

Estimates of genetic parameters and breeding values for New Zealand and Australian Angus cattle

Genetic parameters and adjustment factors for birth, weaning, yearling and final weight were estimated for the New Zealand Angus population, fitting an animal model including maternal genetic and permanent environmental effects as additional random effects. Overall, pooled covariance matrices agreed well with those for Australian Angus, though heritability estimates for birth weight were somewhat lower than in Australian Angus. BREEDPLAN estimates of breeding values and their accuracies were obtained for each population separately. Correlations between estimates for sires with accurate proofs in both countries agreed with their expectations, giving no indication of a genotype x environment interaction. A joint genetic evaluation using adjustment factors specific to each country but the same covariance matrices is recommended.

Paternal half-sib heritabilities and genetic, environmental, and phenotypic correlation estimates from randomly selected Hereford cattle

Growth and carcass data were collected during 10 yr at the Fort Keogh Livestock and Range Research Laboratory in Miles City, MT from a Hereford herd selected at random. The objective was to compare genetic parameter estimates from this randomly selected herd with estimates from published selection studies. Only bulls were included in the data set. Bulls were slaughtered between 14 and 17 mo of age. Genetic parameters were estimated by the paternal half-sib procedure. Data were subdivided into three subgroups: 1) all bulls that had birth weights, 2) bulls with complete records for growth traits, and 3) bulls with complete carcass and growth records. The heritability estimate for birth weight on 736 progeny from 86 sires was .18. The second group included 616 progeny representing 85 sires and heritability estimates were weaning weight, .17; daily gain from birth to weaning, .20; final test weight, .42; and daily gain on test, .47. The third group included 401 progeny from 75 sires and heritability estimates were carcass weight, .38; longissimus muscle area, .51; marbling, .31; slaughter weight, .42; and dressing percentage, .25. Thus, these estimates of heritability were in quite good agreement with previously published values, with a tendency for these estimates to be lower for early growth weights. Phenotypic and environmental correlations were in good agreement and genetic correlations were in general agreement with the data reviewed. Estimates of heritabilities from this herd selected at random were not larger than previous estimates from selected herds.

Genetic and environmental parameters for mature weight and other growth measures in Polled Hereford cattle.

Variances and covariances were estimated for birth weight (BWT), weaning weight (WW), yearling gain (YG), yearling weight (YW), yearling height (YH), relative growth from birth to weaning (RGW) and weaning to yearling (RGY), and mature weight (MW). Field records on 572,446 Polled Hereford cattle were analyzed. Because multiple dam weights were collected on a cow the MW used in the analysis was calculated using a nonlinear regression correction factor computed by fitting a quadratic with a plateau to the data. If the cow had an observation(s) beyond the inflection point (IP), the closest weight to that point was used. If the cow only had observation(s) before the IP the closest weight to that point was nonlinearly adjusted to the plateau. The IP for this data set was 1,506 d and the plateau was 554.7 kg. Heritabilities and genetic and environmental correlations were calculated from the appropriate (co)variances and phenotypic correlations were computed. Heritability estimates for BWT, WW, YG, YW, YH, RGW, RGY, and MW were .49, .24, .23, .30, .59, .24, .15, and .52, respectively. Genetic correlations between MW with BWT, WW, YG, YW, YH, RGW, and RGY were .64, .80, .76, .89, .73, -.29, and .35, respectively, environmental correlations were .15, .43, .05, .40, 1.03, .32, and -.10, respectively, and phenotypic correlations were .33, .32, .28, .46, .70, .00, and .07, respectively.

Genetic parameters for nuclear and nonnuclear inheritance in three synthetic lines of beef cattle differing in mature size

Genetic parameters for nuclear and cytoplasmic genetic effects were estimated from preweaning growth data collected on three synthetic lines of beef cattle differing in mature size. Lines of small-, medium-, and large-framed calves were represented in each of two research herds (Rhodes and McNay). Variance components were estimated separately by herd and size line for birth weight and 205-d weight (WW) by REML with an animal mode using an average of 847 and 427 calf records from Rhodes and McNay, respectively. Model 1 included effects of fixed year, sex of calf, age of dam, and random additive direct (a), additive maternal genetic (m), covariance (a,m), permanent environment affecting the dam, and residual error. Model 2 differed from Model 1 by including random cytoplasmic lineage effects and by ignoring permanent environmental effects. Model 1--direct (maternal) heritability estimates for birth weight at Rhodes were .62(.03) for small, .67(.06) for medium, and .30(.11) for large lines. Genetic correlations between direct and maternal effects for birth weight were .67, -.16, and .48 for the respective size groups. For WW at Rhodes, direct (maternal) heritability estimates were .30(.29), .30(.14), and .10(.16) for small, medium, and large lines, respectively, with genetic correlations of -.34 (small), -.12 (medium), and .17 (large). Heritability estimates at McNay were similar to those at Rhodes, except that maternal genetic heritabilities for WW were smaller (.10, small; .01, medium; .00, large). Model 2--estimates for nuclear genetic effects were consistent with the estimates from Model 1. Cytoplasmic variance accounted for 0 to 5% of the total random variance in birth weight. For WW, cytoplasmic variance was negligible at Rhodes and accounted for 4% of the total random variance in the large line at McNay, averaging less than the permanent environment. Results failed to indicate that cytoplasmic variance was important for preweaning performance.