RESUMO -Visando melhor entendimento das características quantitativas ligadas ao crescimento do gado Nelore, foi realizado estudo das estimativas de componentes de variância e coeficientes de herdabilidade para ganhos de peso nas idades padronizadas de 120 a 240, 240 a 365, 365 a 455 e 455 a 550 dias e ganhos de perímetro escrotal nas idades padronizadas de 365 a 455 e 455 a 550 dias. Componentes de covariância e correlações entre as características de ganho de peso e ganho de perímetro escrotal também foram estimados. Foram utilizados 29.769 registros de ganhos de peso e 15.676 registros de ganhos de perímetro escrotal de animais participantes do PMGRN, entre os anos de 1986 e 1999. As estimativas dos componentes de (co)variância foram obtidas pelo método da máxima verossimilhança restrita, com algoritmo livre de derivadas, sob modelo animal. As estimativas obtidas foram: 0,32 de herdabilidade direta e 0,13 de herdabilidade materna para ganho de peso entre 120 e 240 dias de idade; 0,16, 0,21 e 0,23 de herdabilidade direta para ganho de peso nas idades de 240 a 365, 365 a 455 e 455 a 550 dias, respectivamente; 0,24 e 0,18 de herdabilidade direta para ganho de perímetro escrotal nas idades de 365 a 455 e 455 a 550 dias, respectivamente; e correlação genética de 0,18 entre os ganhos de peso e de perímetro escrotal.Palavras-chave: bovinos, componentes de (co)variância, ganhos de perímetro escrotal, ganhos de peso, Nelore Study of Quantitative Growth Traits from 120 to 550 Days of Age in Nellore CattleABSTRACT -With the aim of a better understanding of quantitative growth traits in Nellore cattle, some parameters were estimated: variance components and heritability coefficients of weight gains between the standardized ages of 120 and 240, 240 and 365, 365 and 455, and 455 and 555 days, and of scrotal circumference gains between the standardized ages of 365 and 455, and 455 and 555 days; and (co)variance components and genetic correlations between weight and scrotal circumference gains. Information from 29,769 records of weight gain and 15,676 records of scrotal circumference gain were analyzed to obtain the (co)variance component estimates. The restricted maximum likelihood, derivative free, under an animal model was the method of choice. The results were the following: 0.32 for the direct genetic heritability and 0.13 for the maternal genetic heritability coefficients for weight gain between 120 and 240 days of age; 0.16, 0.22 and 0.23 for the direct genetic heritability coefficients for weight gain between the ages of 240 and 365, 365 and 455, and 455 and 550 days respectively; 0.24 and 0.18 for the direct genetic heritability coefficients for scrotal circumference gain between the ages of 365 and 455, and 455 and 550 respectively; and genetic correlation of 0.18 between the weight and the scrotal circumference gains. ., v.31, n.2, p.668-674, 2002 Introdução A produção de carne de forma eficiente é o principal objetivo das criações domésticas de bovinos de corte. Assim, o estudo detalhado das fases de ganho de pe...

The Y-encoded, testis-specific protein (TSPY) is a Y-specific gene. The copy numbers of TSPY range from 20 to 60 in men and up to 200 in bulls. In this study, we examined the possibility of using the TSPY gene to sex cattle. DNA from blood samples of 100 Nelore cattle (50 males and 50 females) from the Nelore Cattle Breeding Program (PMGRN) was screened for TSPY by PCR using TSPY-specific primers. The assay was highly specific since all male samples were TSPY-positive and all female samples were negative. Positive results were also obtained at low DNA concentrations (less than 1 ρg/µL). These results showed that TSPY was a good male-specific marker, the usefulness of which was enhanced by the high copy number of the gene. This is the first report to demonstrate the applicability of TSPY for sexing cattle.

These results evidence a bovine transplacental fetal DNA passage.

The CCCTC -binding factor (CTCF) is a protein involved in repression, activation, hormone-inducible gene silencing, functional reading of imprinted genes and X-chromosome inactivation. We analyzed CTCF gene expression in bovine peripheral blood, oocytes and in different cellular stages (2-4 cells, 8-16 cells, 16-32 cells, morulae, and blastocysts) of in vitro fertilized embryos. This is the first report of CTCF expression in oocytes and preimplantation bovine embryos and has implications for the production of embryonic stem cells and the development of novel medical technologies for humans.