Navegando por Autor "Sesana, Roberta Cristina"

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    Economic values for milk production and quality traits in south and southeast regions of Brazil
    (2014) Cardoso, Vera Lucia; Lima, Maria Lucia Pereira; Nogueira, José Ramos; Carneiro, Raul Lara Resende de; Sesana, Roberta Cristina; Oliveira, Elisa Junqueira; El Faro, Lenira
    The objective of this study was to calculate economic values for milk (MY), protein (PY) and fat productions (FY) and somatic cell count (SCC) which could be used to compose an economic index to rank animals involved in an international genetic evaluation program of Holstein cattle used in the commercial dairy population in Brazil. The main milk production systems (MPS) prevailing in the South and Southeast were defined based on the feeding management and production level of herds. To calculate feeding costs, energy requirements for the production of one kg of milk with the respective average protein and fat contents of each MPS were calculated. Feeding costs were obtained based on the regional prices of the diets' components. To calculate revenues, milk prices were obtained from the payment tables practiced by seven milk industries. Economic values were calculated from the marginal differences between revenues and costs, for the interest of maximizing the profit, assuming a fixed number of animals in the herd. The average economic values (R$) for MY, PY and FY were 0.51, 6.41 and 1.94, respectively. The economic impact of increasing the original SCC values in the individual records of cows in the population by 1% was -R$ 1.40 per cow, per year. Due to changes observed in the last years in the milk market in Brazil, selection for milk components became economically advantageous. As a result, the calculation of economic values and the proposition of an economic index based on these traits became feasible. Somatic cell count does have an economic impact on the final price of milk and consequently on the annual profit of herds. It has also been used in breeding programs as an indicator of mastitis resistance and should not be neglected in breeding programs of dairy cattle.
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    Genetic parameters for milk, fat and protein yields in Murrah buffaloes (Bubalus bubalis Artiodactyla, Bovidae)
    (2010) Aspilcueta-Borquis, Rusbel Raúl; Sesana, Roberta Cristina; Berrocal, Milthon Honorio Munoz; Seno, Leonardo de Oliveira; Bignardi, Annaiza Braga; El Faro, Lenira; Albuquerque, Lucia Galvão de; Camargo, Gregório Miguel Ferreira de; Tonhati, Humberto
    The objective of the present study was to estimate genetic parameters for test-day milk, fat and protein yields and 305-day-yields in Murrah buffaloes. 4,757 complete lactations of Murrah buffaloes were analyzed. Co-variance components were estimated by the restricted maximum likelihood method. The models included additive direct genetic and permanent environmental effects as random effects, and the fixed effects of contemporary group, milking number and age of the cow at calving as linear and quadratic covariables. Contemporary groups were defined by herd-year-month of test for test-day yields and by herd-year-season of calving for 305-day yields. The heritability estimates obtained by two-trait analysis ranged from 0.15 to 0.24 for milk, 0.16 to 0.23 for protein and 0.13 to 0.22 for fat, yields. Genetic and phenotypic correlations were all positive. The observed population additive genetic variation indicated that selection might be an effective tool in changing population means in milk, fat and protein yields.
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    Genetic parameters for milk, fat and protein yields in Murrah buffaloes (Bubalus bubalis Artiodactyla, Bovidae)
    (2010) Aspilcueta-Borquis, Rusbel Raúl; Sesana, Roberta Cristina; Berrocal, Milthon Honorio Munoz; Seno, Leonardo de Oliveira; Bignardi, Annaiza Braga; El Faro, Lenira; Albuquerque, Lucia Galvão de; Camargo, Gregório Miguel Ferreira de; Tonhati, Humberto
    The objective of the present study was to estimate genetic parameters for test-day milk, fat and protein yields and 305-day-yields in Murrah buffaloes. 4,757 complete lactations of Murrah buffaloes were analyzed. Co-variance components were estimated by the restricted maximum likelihood method. The models included additive direct genetic and permanent environmental effects as random effects, and the fixed effects of contemporary group, milking number and age of the cow at calving as linear and quadratic covariables. Contemporary groups were defined by herd-year-month of test for test-day yields and by herd-year-season of calving for 305-day yields. The heritability estimates obtained by two-trait analysis ranged from 0.15 to 0.24 for milk, 0.16 to 0.23 for protein and 0.13 to 0.22 for fat, yields. Genetic and phenotypic correlations were all positive. The observed population additive genetic variation indicated that selection might be an effective tool in changing population means in milk, fat and protein yields.