ABSTRACT
Estimates of heritability and phenotypic and genetic correlations between egg number, weight, specific gravity, mass, and estimated shell weight were obtained, along with phenotypic and genetic correlations of specific gravity and weight with body weight, weight change, metabolizable energy intake, residual feed consumption, and weight and age at sexual maturity. Data were from 350 White Leghorn hens by 50 sires and 175 dams. Heritabilities of the egg traits ranged from 0.20 to 0.55, increasing with age of bird from 26 to 54 weeks of age. Their standard errors ranged from 0.07 (all data) to 0.17 (26 to 29 weeks). Phenotypic correlations ranged from 0.80 to -0.13, and genetic correlations from 0.91 to -0.27, depending on egg trait. The highest phenotypic and genetic correlations were between egg number and mass. Genetic correlations for specific gravity and estimated shell weight were, with body weight, -0.02 and 0.56; weight change, 0.29 and 0.44; daily metabolizable energy intake, -0.10 and 0.33; residual consumption, -0.16 and 0.11; age at sexual maturity, -0.61 and -0.46, and weight at sexual maturity, 0.02 and 0.63. Results should contribute to the design of efficient selection programs for economically important traits in hens.
Subject(s)
Animals , Female , Chickens/genetics , Eggs , Egg Shell , Energy Intake , Phenotype , Sexual MaturationABSTRACT
Foram analisados dados de 1.723 registros de 483 vacas da raça Pitangueiras. A raça Pitangueiras foi sintetisada pelo cruzamento de machos puros Red Poll (RP) com fêmeas 1/4 Red Poll x 3/4 Zebu, na área tropical úmidda da cidade de Pitangueiras, perto de Säo Paulo, Brasil. A duraçäo média da lactaçäo foi de 281 dias (variando de 100 a 390), com uma produçäo leiteira média de 2.835 kg. A análise de variância pelo método dos quadrados mínimos mostrou que os animais mais velhos tiveram lactaçöes mais prolongadas (de 17,2 a 50,7 dias), acima de média, o mesmo ocorrendo com os animais paridos na época seca (de 0,6 a 9,8 dias). A repetibilidade estimada pela correlaçäo intraclasse foi de 0,15 ñ 0,06. As herdabilidades para duraçäo da lactaçäo estimadas a partir das correlaçöes entre meio-irmäos paternos foram de 0,33 ñ 0,22 para a primeira lactaçäo, 0,34 ñ 0,25 para a segunda e 0,16 ñ 0,28 para a terceira. A estimativa global foi de 0,29