Estimates of genetic parameters for stayability and their associations with traits of economic interest in Gir dairy cows.

The objective of the present study was to estimate genetic parameters for stayability at 60 months of age (STAY60) and its association with first lactation cumulative milk yield (P305), age at first calving (AFC), and first calving interval (FCI), in order to adopt these traits as selection criteria for longevity in Gir dairy cattle. Records for 2770 cows born between 1982 and 2008 from six herds in the Brazilian states of Minas Gerais, São Paulo, and Paraíba were analyzed. The (co)variance components were estimated by a Bayesian approach using bivariate animal models. The heritability estimates were 0.37 ± 0.09, 0.23 ± 0.04, 0.26 ± 0.06, and 0.07 ± 0.03 for STAY60, P305, AFC, and FCI, respectively. The genetic correlations of STAY60 with P305, AFC, and FCI were moderate to high, with values of 0.61 (0.17), -0.44 (0.23), and 0.88 (0.13), respectively. STAY60, P305, and AFC exhibited additive genetic variability, and these traits should be considered in selection indices. The indirect selection for longevity through the correlated responses of early-expression traits, such as milk production at first lactation, could be used to improve the ability of animals to remain in the herd.

Strategies of rotational stocking management on weight gain and productivity of heifers grazing on marandu palisade grass / Estratégia de manejo em pastejo rotacionado no ganho de peso e produtividade de novilhas pastejando capim marandu

Pasture management can affect plant growth and interfere with the performance of the animals or the productivity of the production system. Marandu palisade grass swards subjected to year-round grazing by crossbred heifers were evaluated. Three stocking systems were tested: 1) a grazing cycle of 28 days (T28d); 2) when the sward reached a pre-grazing height of 30 cm (T0.3m), and 3) when the sward reached a pre-grazing height of 30 cm under irrigation (T-irrig0.3m). Heifers from treatments T28d and T0.3m were supplemented with dry matter at 1% of BW during winter. Statistical was a completely randomized block split-plot design. The light interception was higher (P<0.001) for T-irrig0.3m during winter. A lower leaf area index (P<0.001) was found for T28d, and T0.3m during winter and for T0.3m during autumn. There was an effect of stocking systems (P=0.0055), season (P<0.001) and interaction (P<0.0001) on weight gain (WG), stocking rate and productivity. The lowest WG was obtained in winter for the T-irrig0.3m treatment. The mean WG was 0.45, 0.49 and 0.43 kg/day for T28d, T0.3m and T-irrig0.3m, respectively. Lower productivity (P=0.0155) was observed for T28d when compared to T0.3m and T-irrig0.3m. The productivity rates were 662.2, 741.7 and 758.3 kg WG/ha, per season for T28d, T0.3m and T-irrig0.3m, respectively...(AU)

O manejo de pastagens pode afetar o crescimento das plantas e interferir no desempenho dos animais ou na produtividade do sistema de produção. Sistemas de pastejo de capim marandu foram avaliados durante um ano, sendo ocupados por novilhas mestiças. Três sistemas de pastejo foram avaliados: 1) ciclos de pastejos fixos com 28 dias (T28d); 2) pastejos iniciados quando a altura da planta era de 30 cm (T0,3m), e 3) pastejos iniciados quando a altura da planta era de 30 cm recebendo irrigação (T-irrig0,3m). As novilhas dos tratamentos T28d e T0,3m foram suplementadas durante o inverno seco em 1% do peso vivo. O delineamento foi em blocos casualisados e medidas repetidas no tempo. A interceptação luminosa foi maior (P<0,001) para T-irrig0,3m durante o inverno. Menor índice de área foliar (P<0,001) foi observada para T28d, eT0,3m no inverno e para T0,3m durante o outono. Houve efeito de sistema de pastejo (P=0,0055), estação do ano (P<0,001) e interação (P<0,0001) no ganho de peso (GP), taxa de lotação e produtividade. O menor GP foi obtido no inverno e no tratamento T-irrig0,3m. As médias de GP foram 0,45, 0,49 e 0,43 kg/dia para T28d, T0,3m e T-irrig0,3m, respectivamente. Menor produtividade (P=0,0155) foi observada em T28d quando comparado com T0,3m e T-irrig0,3m. As produtividades foram 662,2, 741,7 e 758,3 kg GP/ha por estação do ano para T28d, T0,3m e T-irrig0,3m, respectivamente...(AU)

Strategies of rotational stocking management on weight gain and productivity of heifers grazing on marandu palisade grass / Estratégia de manejo em pastejo rotacionado no ganho de peso e produtividade de novilhas pastejando capim marandu

Pasture management can affect plant growth and interfere with the performance of the animals or the productivity of the production system. Marandu palisade grass swards subjected to year-round grazing by crossbred heifers were evaluated. Three stocking systems were tested: 1) a grazing cycle of 28 days (T28d); 2) when the sward reached a pre-grazing height of 30 cm (T0.3m), and 3) when the sward reached a pre-grazing height of 30 cm under irrigation (T-irrig0.3m). Heifers from treatments T28d and T0.3m were supplemented with dry matter at 1% of BW during winter. Statistical was a completely randomized block split-plot design. The light interception was higher (P<0.001) for T-irrig0.3m during winter. A lower leaf area index (P<0.001) was found for T28d, and T0.3m during winter and for T0.3m during autumn. There was an effect of stocking systems (P=0.0055), season (P<0.001) and interaction (P<0.0001) on weight gain (WG), stocking rate and productivity. The lowest WG was obtained in winter for the T-irrig0.3m treatment. The mean WG was 0.45, 0.49 and 0.43 kg/day for T28d, T0.3m and T-irrig0.3m, respectively. Lower productivity (P=0.0155) was observed for T28d when compared to T0.3m and T-irrig0.3m. The productivity rates were 662.2, 741.7 and 758.3 kg WG/ha, per season for T28d, T0.3m and T-irrig0.3m, respectively...

O manejo de pastagens pode afetar o crescimento das plantas e interferir no desempenho dos animais ou na produtividade do sistema de produção. Sistemas de pastejo de capim marandu foram avaliados durante um ano, sendo ocupados por novilhas mestiças. Três sistemas de pastejo foram avaliados: 1) ciclos de pastejos fixos com 28 dias (T28d); 2) pastejos iniciados quando a altura da planta era de 30 cm (T0,3m), e 3) pastejos iniciados quando a altura da planta era de 30 cm recebendo irrigação (T-irrig0,3m). As novilhas dos tratamentos T28d e T0,3m foram suplementadas durante o inverno seco em 1% do peso vivo. O delineamento foi em blocos casualisados e medidas repetidas no tempo. A interceptação luminosa foi maior (P<0,001) para T-irrig0,3m durante o inverno. Menor índice de área foliar (P<0,001) foi observada para T28d, eT0,3m no inverno e para T0,3m durante o outono. Houve efeito de sistema de pastejo (P=0,0055), estação do ano (P<0,001) e interação (P<0,0001) no ganho de peso (GP), taxa de lotação e produtividade. O menor GP foi obtido no inverno e no tratamento T-irrig0,3m. As médias de GP foram 0,45, 0,49 e 0,43 kg/dia para T28d, T0,3m e T-irrig0,3m, respectivamente. Menor produtividade (P=0,0155) foi observada em T28d quando comparado com T0,3m e T-irrig0,3m. As produtividades foram 662,2, 741,7 e 758,3 kg GP/ha por estação do ano para T28d, T0,3m e T-irrig0,3m, respectivamente...

Genetic parameters for milk production traits and breeding goals for Gir dairy cattle in Brazil.

To implement an animal breeding program, it is important to define the production circumstances of the animals of interest to determine which traits of economic interest will be selected for the breeding goal. The present study defined breeding goals and proposed selection indices for milk production and quality traits of Gir dairy cattle. First, a bioeconomic model was developed to calculate economic values. The genetic and phenotypic parameters were estimated based on records from 22,468 first-lactation Gir dairy cows and their crosses for which calving occurred between 1970 and 2011. Statistical analyses were carried out for the animal model, with multitrait analyses using the restricted maximum likelihood method. Two situations were created in the present study to define the breeding goals: 1) including only milk yield in the breeding goal (HGL1) and 2) including fat and protein in addition to the milk yield (HGL2). The heritability estimates for milk, protein, and fat production were 0.33 ± 0.02, 0.26 ± 0.02, and 0.24 ± 0.02, respectively. All phenotypic and genetic correlations were highly positive. The economic values for milk, fat, and protein were US$0.18, US$0.27, and US$7.04, respectively. The expected economic responses for HGL2 and for HGL1 were US$126.30 and US$79.82, respectively. These results indicate that milk component traits should be included in a selection index to rank animals evaluated in the National Gir Dairy Breeding Program developed in Brazil.

Comparison of factor-analytic and reduced rank models for test-day milk yield in Gyr dairy cattle (Bos indicus).

We analyzed 46,161 monthly test-day records of milk production from 7453 first lactations of crossbred dairy Gyr (Bos indicus) x Holstein cows. The following seven models were compared: standard multivariate model (M10), three reduced rank models fitting the first 2, 3, or 4 genetic principal components, and three models considering a 2-, 3-, or 4-factor structure for the genetic covariance matrix. Full rank residual covariance matrices were considered for all models. The model fitting the first two principal components (PC2) was the best according to the model selection criteria. Similar phenotypic, genetic, and residual variances were obtained with models M10 and PC2. The heritability estimates ranged from 0.14 to 0.21 and from 0.13 to 0.21 for models M10 and PC2, respectively. The genetic correlations obtained with model PC2 were slightly higher than those estimated with model M10. PC2 markedly reduced the number of parameters estimated and the time spent to reach convergence. We concluded that two principal components are sufficient to model the structure of genetic covariances between test-day milk yields.

Random regression models using Legendre polynomials or linear splines for test-day milk yield of dairy Gyr (Bos indicus) cattle.

Studies investigating the use of random regression models for genetic evaluation of milk production in Zebu cattle are scarce. In this study, 59,744 test-day milk yield records from 7,810 first lactations of purebred dairy Gyr (Bos indicus) and crossbred (dairy Gyr × Holstein) cows were used to compare random regression models in which additive genetic and permanent environmental effects were modeled using orthogonal Legendre polynomials or linear spline functions. Residual variances were modeled considering 1, 5, or 10 classes of days in milk. Five classes fitted the changes in residual variances over the lactation adequately and were used for model comparison. The model that fitted linear spline functions with 6 knots provided the lowest sum of residual variances across lactation. On the other hand, according to the deviance information criterion (DIC) and bayesian information criterion (BIC), a model using third-order and fourth-order Legendre polynomials for additive genetic and permanent environmental effects, respectively, provided the best fit. However, the high rank correlation (0.998) between this model and that applying third-order Legendre polynomials for additive genetic and permanent environmental effects, indicates that, in practice, the same bulls would be selected by both models. The last model, which is less parameterized, is a parsimonious option for fitting dairy Gyr breed test-day milk yield records.

Milk yield persistency in Brazilian Gyr cattle based on a random regression model.

With the objective of evaluating measures of milk yield persistency, 27,000 test-day milk yield records from 3362 first lactations of Brazilian Gyr cows that calved between 1990 and 2007 were analyzed with a random regression model. Random, additive genetic and permanent environmental effects were modeled using Legendre polynomials of order 4 and 5, respectively. Residual variance was modeled using five classes. The average lactation curve was modeled using a fourth-order Legendre polynomial. Heritability estimates for measures of persistency ranged from 0.10 to 0.25. Genetic correlations between measures of persistency and 305-day milk yield (Y305) ranged from -0.52 to 0.03. At high selection intensities for persistency measures and Y305, few animals were selected in common. As the selection intensity for the two traits decreased, a higher percentage of animals were selected in common. The average predicted breeding values for Y305 according to year of birth of the cows had a substantial annual genetic gain. In contrast, no improvement in the average persistency breeding value was observed. We conclude that selection for total milk yield during lactation does not identify bulls or cows that are genetically superior in terms of milk yield persistency. A measure of persistency represented by the sum of deviations of estimated breeding value for days 31 to 280 in relation to estimated breeding value for day 30 should be preferred in genetic evaluations of this trait in the Gyr breed, since this measure showed a medium heritability and a genetic correlation with 305-day milk yield close to zero. In addition, this measure is more adequate at the time of peak lactation, which occurs between days 25 and 30 after calving in this breed.

Parâmetros genéticos entre características de leite, de peso e a idade ao primeiro parto em gado mestiço leiteiro (Bos taurus x Bos indicus) / Genetic parameters between milk traits, weight traits and age at first calving in crossbreed dairy cattle (Bos taurus x Bos indicus)

Foram estimadas as correlações genéticas entre características de produção de leite (produção de leite, gordura, proteína e duração da lactação em até 305 dias, na primeira lactação), características de peso (taxa de crescimento de novilhas entre 12-24 meses e peso médio de vacas) e idade ao primeiro parto, em uma população de fêmeas Mestiço Leiteiro Brasileiro (MLB), por meio de metodologia REML, sob modelo animal. As estimativas de herdabilidade das características estudadas na ordem acima foram, respectivamente, 0,28± 0,08, 0,30±0,11, 0,28±0,09, 0,19±0,07, 0,18±0,06, 0,42±0,10 e 0,48±0,12. As correlações genéticas entre peso médio da vaca e a produção de leite, gordura e proteína foram, respectivamente, -0,22±0,22, -0,49±0,31 e -0,22±0,23 e da taxa de crescimento das novilhas com a produção de leite, gordura e proteína foram respectivamente, -0,59±0,35, -0,73±0,44 e -0,62±0,37. As correlações genéticas entre produção de leite, peso médio das vacas e taxa de crescimento das novilhas com idade ao primeiro parto foram respectivamente, 0,05±0,18, -0,05±0,18 e 0,02±0,20. A alta correlação genética (0,93±0,02) entre produção de leite e duração da lactação indicou que não se deve remover a variação na duração da lactação na seleção de gado leiteiro tropical(AU)

Genetic correlations between milk production (milk, fat, protein yield lactation length in 305-d lactation), live weight (average cow live weight, growth rate between 12-24 mo) and age at first calving traits were estimated in a population of Mestiço Leiteiro Brasileiro (MLB) females using REML methodology and animal model. The estimates of heritability were respectively, 0.28± 0.08, 0.30±0.11, 0.28±0.09, 0.19±0.07, 0.18±0.06, 0.42±0.10 and 0.48±0.12 for those traits. Genetic correlations between milk, fat and protein yield with cow average weight were, respectively, -0.22±0.22, -0.49±0.31, -0.22±0.23, and between milk, fat and protein yield with heifer live weight gain, -0.59±0.35, -0.73±0.44, -0.62±0.37 as well. Genetic correlations between milk yield, cow average weight and heifer live weight gain with age at first calving were, respectively, 0.05±0.18, -0.05±0.18, 0.02±0.20. The high genetic correlation between milk production and lactation length (0.93±0.02) indicated that variation of the lactation length should not be removed when selecting tropical dairy cattle(AU)

Parâmetros genéticos entre características de leite, de peso e a idade ao primeiro parto em gado mestiço leiteiro (Bos taurus x Bos indicus) / Genetic parameters between milk traits, weight traits and age at first calving in crossbreed dairy cattle (Bos taurus x Bos indicus)

Foram estimadas as correlações genéticas entre características de produção de leite (produção de leite, gordura, proteína e duração da lactação em até 305 dias, na primeira lactação), características de peso (taxa de crescimento de novilhas entre 12-24 meses e peso médio de vacas) e idade ao primeiro parto, em uma população de fêmeas Mestiço Leiteiro Brasileiro (MLB), por meio de metodologia REML, sob modelo animal. As estimativas de herdabilidade das características estudadas na ordem acima foram, respectivamente, 0,28± 0,08, 0,30±0,11, 0,28±0,09, 0,19±0,07, 0,18±0,06, 0,42±0,10 e 0,48±0,12. As correlações genéticas entre peso médio da vaca e a produção de leite, gordura e proteína foram, respectivamente, -0,22±0,22, -0,49±0,31 e -0,22±0,23 e da taxa de crescimento das novilhas com a produção de leite, gordura e proteína foram respectivamente, -0,59±0,35, -0,73±0,44 e -0,62±0,37. As correlações genéticas entre produção de leite, peso médio das vacas e taxa de crescimento das novilhas com idade ao primeiro parto foram respectivamente, 0,05±0,18, -0,05±0,18 e 0,02±0,20. A alta correlação genética (0,93±0,02) entre produção de leite e duração da lactação indicou que não se deve remover a variação na duração da lactação na seleção de gado leiteiro tropical

Genetic correlations between milk production (milk, fat, protein yield lactation length in 305-d lactation), live weight (average cow live weight, growth rate between 12-24 mo) and age at first calving traits were estimated in a population of Mestiço Leiteiro Brasileiro (MLB) females using REML methodology and animal model. The estimates of heritability were respectively, 0.28± 0.08, 0.30±0.11, 0.28±0.09, 0.19±0.07, 0.18±0.06, 0.42±0.10 and 0.48±0.12 for those traits. Genetic correlations between milk, fat and protein yield with cow average weight were, respectively, -0.22±0.22, -0.49±0.31, -0.22±0.23, and between milk, fat and protein yield with heifer live weight gain, -0.59±0.35, -0.73±0.44, -0.62±0.37 as well. Genetic correlations between milk yield, cow average weight and heifer live weight gain with age at first calving were, respectively, 0.05±0.18, -0.05±0.18, 0.02±0.20. The high genetic correlation between milk production and lactation length (0.93±0.02) indicated that variation of the lactation length should not be removed when selecting tropical dairy cattle

Estrutura populacional do rebanho Tabapuä registrado no Brasil / Population structure of the registered Tabapuä cattle in Brazil

Descreveu-se a estrutura da populaçäo do rebanho Tabapuä registrado no Brasil. Foram geradas estatísticas descritivas da distribuiçäo do número de progênies e estimados o intervalo de geraçöes, estatísticas de F, número efetivo de fundadores, de ancestrais e de genomas remanescentes, além do tamanho efetivo da populaçäo, usando o registro genealógico de animais nascidos entre 1971-1998. Entre 1994 e 1998 foram registrados 37.778 animais, 18.736 machos e 19.042 fêmeas, pertencentes a 136 criadores. As médias dos intervalos de geraçöes estimadas para os períodos de 1979-1983, 1984-1988, 1989-1993 e 1994-1998 foram, respectivamente, 6,26; 7,18; 7,68 e 7,56 anos para pais-filhos e 6,18; 6,43; 6,99 e 7,27 para pais-pais. O tamanho efetivo da populaçäo e o número efetivo de fundadores, de ancestrais e de genomas remanescentes em cada um dos períodos foram, respectivamente, 378, 218, 213 e 181; 131, 254, 202 e 163; 73, 150, 119 e 94 e 55, 112, 78 e 61

Estrutura populacional da raça Nelore Mocho / Population structure of the Polled Nelore breed

Descreveu-se a estrutura populacional da raça Nelore Mocho utilizando dados do registro genealógico de animais nascidos entre 1969 e 1998. O banco de dados foi separado em quatro períodos de 1979-1983, 1984-1988, 1989-1993 e 1994-1998. Calcularam-se as estatísticas descritivas do número de criadores, de reprodutores e de reprodutrizes. A endogamia total aumentou de 0,55 por cento para 0,98 por cento, a esperada sob acasalamento ao acaso aumentou de 0,11 por cento para 0,56 por cento e a endogamia devido à subdivisäo populacional permaneceu constante, ao redor de 0,45 por cento, indicando que a subdivisäo genética da raça Nelore Mocho é próxima a zero e praticamente inexistente. O tamanho efetivo populacional foi estimado pelo coeficiente total de endogamia e permaneceu ao redor de 120. A inclusäo de animais no livro genealógico aumentou de 4.630 para 13.907, entretanto, esta açäo näo foi suficiente para incrementar o tamanho efetivo. Baseado na probabilidade de origem do gene foram calculados o número efetivo de fundadores, de ancestrais e de genomas remanescentes. Esses parâmetros decresceram ao longo do período, atingindo valores de 144, 98 e 64. Todas as estimativas foram análogas na descriçäo da estrutura genética populacional e devem ser consideradas no futuro para o desenvolvimento de programas de seleçäo

Estrutura populacional do rebanho Tabapuã registrado no Brasil

The population structure of the registered Tabapuã cattle in Brazil was described. Descriptive statistics of the distribution of the number of progeny, the generation interval, F-statistics, effective number of founders, ancestors, reminiscent genomes and effective population size were estimated using pedigree records from registered animals from 1971 to 1998. In the last period studied (1994-1998), 37,778 animals, 18,736 males and 19,042 females from 136 breeders were registered. The generations intervals calculated in each of the four periods 1979-1983, 1984-1988, 1989-1993 and 1994-1998 were, respectively, 6.26, 7.18, 7.68 and 7.56 yr for parent-progeny and 6.18, 6.43, 6.99 and 7.27 yr for parent to parent. The effective size of the population, founders, ancestors and reminiscent genomes in each of these periods were respectively: 378, 218, 213 and 181; 131, 254, 202 and 163; 73, 150, 119 and 94; 55, 112, 78 and 61.

Descreveu-se a estrutura da população do rebanho Tabapuã registrado no Brasil. Foram geradas estatísticas descritivas da distribuição do número de progênies e estimados o intervalo de gerações, estatísticas de F, número efetivo de fundadores, de ancestrais e de genomas remanescentes, além do tamanho efetivo da população, usando o registro genealógico de animais nascidos entre 1971-1998. Entre 1994 e 1998 foram registrados 37.778 animais, 18.736 machos e 19.042 fêmeas, pertencentes a 136 criadores. As médias dos intervalos de gerações estimadas para os períodos de 1979-1983, 1984-1988, 1989-1993 e 1994-1998 foram, respectivamente, 6,26; 7,18; 7,68 e 7,56 anos para pais-filhos e 6,18; 6,43; 6,99 e 7,27 para pais-pais. O tamanho efetivo da população e o número efetivo de fundadores, de ancestrais e de genomas remanescentes em cada um dos períodos foram, respectivamente, 378, 218, 213 e 181; 131, 254, 202 e 163; 73, 150, 119 e 94 e 55, 112, 78 e 61.

Estrutura populacional da raça Nelore Mocho

The population structure of the Polled Nelore breed using pedigree records from animals registered from 1969 to 1998 was described. The data file was divided in the following periods: 1979-1983, 1984-1988, 1989-1993 and 1994-1998. Descriptive statistics of the number of breeders, sires and dams were calculated. The total inbreeding increased from 0.55% to 0.98%, the inbreeding expected under random mating increased from 0.11% to 0.56%, and the inbreeding due to population subdivision was constantly around 0.45%, indicating that genetic subdivisions of the Polled Nelore breed is near to zero and quite irrelevant. The effective population size estimated from the total inbreeding was around 120. The upgrading of non-registered animals increased from 4,630 to 13,907 animals, however, this action was not enough to increase the effective population size. Based on probabilities of gene origin the effective numbers of founders, ancestors and remaining genomes were calculated. These parameters decreased over the period reaching values of 144, 98 and 64. All the estimates were analogous in the description of the population genetic structure and should be considered in developing future selection programs.

Descreveu-se a estrutura populacional da raça Nelore Mocho utilizando dados do registro genealógico de animais nascidos entre 1969 e 1998. O banco de dados foi separado em quatro períodos de 1979-1983, 1984-1988, 1989-1993 e 1994-1998. Calcularam-se as estatísticas descritivas do número de criadores, de reprodutores e de reprodutrizes. A endogamia total aumentou de 0,55% para 0,98%, a esperada sob acasalamento ao acaso aumentou de 0,11% para 0,56% e a endogamia devido à subdivisão populacional permaneceu constante, ao redor de 0,45%, indicando que a subdivisão genética da raça Nelore Mocho é próxima a zero e praticamente inexistente. O tamanho efetivo populacional foi estimado pelo coeficiente total de endogamia e permaneceu ao redor de 120. A inclusão de animais no livro genealógico aumentou de 4.630 para 13.907, entretanto, esta ação não foi suficiente para incrementar o tamanho efetivo. Baseado na probabilidade de origem do gene foram calculados o número efetivo de fundadores, de ancestrais e de genomas remanescentes. Esses parâmetros decresceram ao longo do período, atingindo valores de 144, 98 e 64. Todas as estimativas foram análogas na descrição da estrutura genética populacional e devem ser consideradas no futuro para o desenvolvimento de programas de seleção.