William José Ferreira

Avaliação genética de bovinos da raça holandesa usando a produção de leite no dia do controle

153,963 test day milk yield records and 13,273 first lactations of Holstein cows calving between 1989 and 1998, were used with the objective of estimating genetic, phenotypic and environmental parameters for test day milk yield (PLDC) and 305 day milk yield (P305) and to study the convenience of using test day yields in genetic evaluations to replace P305. Four models were used. Models 1 and 2 differed according contemporary grouping and monthly milk records were considered as repeated measures. In model 1 (PLDCM01) records were grouped by herd-year-season of test day yield and in model 2 (PLDCM02) by herd-year-season of calving. In a third (model 3), monthly yield records were analyzed as individual traits (C01 to C10); and the fourth (model 4) was the traditional 305-day model. Restricted Maximum Likelihood methodology was used with the MTDFREML system. The estimates of heritability for PLDC, using model 1, model 2 and for P305 were 0.27, 0.15 and 0.25, respectively. Heritabilities for monthly milk records ranged from 0.11+0.02 (C01) to 0.21+0.03 (C08), with the largest values occurring beginning in the fourth month. Genetic correlation estimates between monthly records and P305 ranged from 0.76 to 1.00, with the highest correlations occurring in the middle lactation. It was concluded that using test day milk yield is promising and that selecting for middle lactation records could have advantages over 305-day milk yield.

Estimação de tendência genética para produção de leite na raça Holandesa no estado de Minas Gerais

Production records from 75,567 lactations of 40,941 Holstein cows in 561 herds from 1980 to 2002 were used. Predicted cow and sire breeding values from an animal model were used to estimate genetic trend considering the four selection paths connecting two generations. The variance component estimates and breeding value predictions were obtained using the MTDFREML program package. The model of analysis accounted for the fixed effects of herd-year-season of calving, genetic group, age of calving as covariate (linear and quadratic) and the random effects of animal, permanent environment and error. The greatest annual genetic gain estimate was 57.7kg/yr for the path of sires of bulls from 1986 to 1991. For the path of dams of bulls, estimates were negative and for dams of cows changed from negative from 1970 to 1985 to 16.9kg/yr, from 1986 to 1999. When all paths of selection were combined, estimated annual genetic gain from 1970 to 1999 was 6.71± 3.78kg, corresponding to 0.1% of the average production. Estimates of genetic trend were much less than theoretically possible.

Efeitos genéticos e de ambiente em um rebanho do ecótipo mantiqueira: II. Características produtivas

Por meio de analises uni e bicaracteristicas entre a producao total de leite (PL), producao de gordura (PROG), porcentagem de gordura (PERG), duracao da lactacao (DL) e periodo seco (PSECO), objetivou-se, com este trabalho, estimar parâmetros geneticos utilizando-se registros provenientes das cinco primeiras lactacoes de 1.406 vacas do ecotipo Mantiqueira, filhas de 113 reprodutores, com partos entre os anos de 1977 e 1997, pertencentes ao programa de melhoramento do Polo Regional do Vale do Paraiba da Agencia Paulista de Tecnologia dos Agronegocios da Secretaria de Agricultura e Abastecimento do Estado de Sao Paulo (APTA/SAA-SP), no municipio de Pindamonhangaba. Os modelos usados para obtencao das medias dos quadrados minimos incluiram os efeitos fixos de ano e estacao de parto e idade ao parto, alem dos efeitos aleatorios de reprodutor e do erro. Para a obtencao dos parâmetros geneticos pela metodologia REML foram utilizados os modelos que ajustavam os efeitos fixos de ano-estacao e idade da vaca ao parto, alem dos efeitos aleatorios de animal e do erro. As medias ajustadas ± erros-padrao foram: 1863,31 ± 1047,19 kg para a PL; 76,59 ± 31,92 kg para a PROG; 3,43 ± 0,64 % para PERG; 231,72 ± 91,30 dias para DL; e 256,40 ± 180,29 dias para o PSECO. As herdabilidades foram: 0,25; 0,09; 0,00; 0,16 e 0,06, respectivamente, para PL, PROG, PERG, DL e PSECO. As correlacoes geneticas entre PL e PROG ou PERG foram, respectivamente, de 0,36 e -0,02. De acordo com os resultados obtidos, pode-se inferir que ha variacao genetica aditiva entre vacas para producao de leite.

Effects of genetics and enviromment on the Mantiqueira type breed: I. Reproductive traits

The reproductive performance of Mantiqueira cows were analyzed using data of records of age of first calving (IPP), calving interval (IDP) and days open (PSERV). These data were the first five lactations of 1406 cows of Mantiqueira ecotype consisting of daughters of 113 sires, with calving from 1952 to 1997, from the Paraiba Valley Regional Center of Research in Sao Paulo State (APTA/SAA-SP) breeding program. Models to obtain least square means included fixed effects for year and season of birth (for IPP) or calving (for IDP and PSERV) and age, in addition to the random effect of sire and error. The models to obtain genetic parameters by REML methodology included fixed effects for year-season and age, in addition to the random effects of animal and error. The least square means ± standard error were 45.60 ± 8.14 months to the IPP, 460.56 ± 122.05 days to the IDP and 181.44 ± 110.31 days to the PSERV. Estimated values of heritabilities were: 0.13 (IPP), 0.01 (IDP), and 0.01 (PSERV).

Ajustamento para Heterogeneidade de Variância da Produção de Leite de Vacas da Raça Holandesa no Estado de Minas Gerais

Utilizou-se para avaliacao genetica de vacas da raca Holandesa no Estado de Minas Gerais um procedimento de ajustamento para heterogeneidade de variância entre rebanhos e ao longo do tempo, com base na variância para producao de leite em cada subclasse rebanho-ano. As variâncias fenotipicas duplicaram com o aumento da media de producao da subclasse de 4.000 para 10.000 kg e cresceram, tambem, com o numero de animais na subclasse. As producoes foram padronizadas para uma variância comum e os valores geneticos obtidos antes e apos o ajustamento, comparados. As variacoes das Capacidades Previstas de Transmissao (PTAs) e ordem dos touros foram pequenas. As correlacoes de ordem entre PTAs de vacas elite foram baixas ate negativas, sendo antes originadas de rebanhos com maior variabilidade e, apos o ajustamento, selecionadas em todas as classes de variabilidade. Com o ajustamento para heterogeneidade da variância, houve aumento de 12 kg/ano na tendencia genetica estimada para a producao de leite. A implementacao do ajustamento para heterogeneidade de variância nas avaliacoes geneticas pode contribuir para a selecao mais precisa de vacas elite no Estado e podera aumentar a taxa de ganho genetico pela selecao de femeas.

Avaliação genética de touros pelo modelo animal, modelo touro e método das companheiras de rebanho

Predicted transmitting ability (PTA) of milk yield of 529 sires using animal model (MA), sire model (MT) and herdmate contemporary comparison method (MCR) were calculated and compared by means of correlations rank and values, reliability, differences among PTA and percent of coincidence in the selection of the best bulls. Two sets of data were considered one contained up to five lactation per cow and other with production data at first lactation. Data of 12,762 lactations of 5757 Gyr and crossbred Gyr Holstein cows were analyzed. Allowing up to five lactation per cow, the rank correlation among PTA calculated using MA and MCR was .69; between MA and MT was .96; and between MT and MCR was .73. The rank correlation between PTA using MA up to five lactation per cow, and PTA calculated by MCR, MT and MA using only the first lactation, were: .60, .76, and .79, respectively. Average reliabilities were greater when animal and sire model were used. These two models were similar in the selection of the best sires according to the PTA values. The estimate reliability when the animal model were used was 11 to 47% greater than the estimated by MCR. These maximum differences were 2% when animal model was compared with sire model.

Análise comparativa de procedimentos metodológicos para a avaliação genética de vacas para a produção de leite

Milk production data of 19,151 lactations from 8,984 cows, daughters of 795 Gyr sires were used to genetically evaluate cows. Mixed model equation was used to predict sire-breeding values that were incorporated in the selection index of the cows. Besides the selection index, animal models were also used to predict the genetic value of the cows, using only the first lactation or up to five lactations per cow. The accuracies of the predictions obtained by cows breeding values, using the animal models, were higher when were used in the evaluation up to five lactations (.76) or only the first lactation (.73) on the accuracies predictions obtained by the selection index (.55 to .59). Similarly, the correlation among the breeding values predicted by selection index and predicted by animal model up to five lactations ranged from .74 to .84. The highest correlation (.84) was observed among the prediction obtained by animal models and the lowest (.74) within the animal model with up to five lactations and the selection index, which the sire-dam breeding values were obtained by the herdmate method. The genetic gain obtained when 20% of best cows were selected to produce descendants for the new generation was at least 80% of the gain obtained by animal model (270 kg), regardless the used procedure.