nan Silva

Interação genótipo × ambiente e estimativas de parâmetros genéticos de características ponderais de bovinos Tabapuã

Dados de pesos aos 205 (P205) e 365 (P365) dias de idade, de 28.946 animais Tabapua, provenientes de 152 fazendas dos diversos estados brasileiros, nascidos no periodo de 1976 a 1995, foram utilizados nesta analise. Foram avaliadas as interacoes genotipo-ambiente, bem como estimadas herdabilidades direta e materna pelo metodo de maxima verossimilhanca restrita em modelo estatistico, que incluiu efeitos fixos de grupo contemporâneo, idade da vaca ao parto (covariavel) e efeitos aleatorios geneticos direto e materno. As estimativas de herdabilidade direta e materna para P205 nas regioes Sul (R1), Sudeste (R2), Centro-Oeste (R3) e Nordeste (R4) foram: 0,02 e 0,31 (R1), 0,17 e 0,19 (R2), 0,20 e 0,09 (R3) e 0,06 e 0,16 (R4). Para P365, foram 0,05 e 0,03 (R1), 0,20 e 0,03 (R2), 0,51 e 0,62 (R3) e 0,15 e 0,05 (R4). As correlacoes geneticas encontradas para as caracteristicas P205 e P365, ambas consideradas caracteristicas distintas nas regioes R1, R2, R3 e R4, foram: 1,00 e 0,99, 0,84 e 0,99, -0,86 e -0,73, 0,98 e 0,93, 0,51 e 0,45, 1,00 e 0,12 para R1/R2, R1/R3, R1/R4, R2/R3, R2/R4 e R3/R4, respectivamente. Esses resultados indicam que, na desmama (P205), o efeito da interacao genotipo x ambiente foi observado somente nas combinacoes que envolveram a regiao Nordeste (R4) e as regioes Sul (R1) e Sudeste (R2). Para pesos pos-desmama (P365), o efeito dessa interacao foi evidenciado em todas as combinacoes que incluiram a regiao Nordeste.

Herdabilidade e correlação genética entre perímetro escrotal, libido e características seminais de touros Nelore

Dados de 273 touros Nelore nascidos de 1992 a 1998 e com idade media de 31 meses foram utilizados para estimar as herdabilidades do perimetro escrotal (PE), libido (Lib), motilidade (mot), vigor (vig), concentracao (con) e taxa de anormalidade seminal (ta) e as correlacoes geneticas entre essas caracteristicas. Com o uso do metodo da maxima verosimilhanca restrita as estimativas de herdabilidade e respectivos erros-padrao foram 0,38±0,20 para PE, 0,33±0,20 e 0,31±0,20 para Lib com idade ou peso corporal no modelo, respectivamente, 0,01±0,10 para mot, 0,03±0,30 para vig, 0,00±0,50 para coN e 0,07±0,13 para ta. As correlacoes geneticas entre PE e Lib foram 0,78 e 0,76, respectivamente, considerando-se ou nao o peso corporal no modelo. Correlacoes geneticas entre PE e as caracteristicas con, mot, vig e ta foram 0,99, 1,00, -0,14 e 0,99, respectivamente. Pode-se esperar resposta a selecao direta para PE e Lib e a selecao para uma das caracteristicas resultaria em selecao para a outra. As baixas estimativas de herdabilidade para as caracteristicas seminais indicam pequeno componente genetico aditivo.

Exigências de proteína bruta e energia metabolizável em codornas de corte durante a fase de crescimento

Crude protein (CP) and metabolizable energy (ME) levels during five experimental periods of seven days each of the growing phase for European quail were determined. A total of 384 quails of both sexes were used in a completely randomized design in a 2×4 (energy and crude protein) factorial treatment with six replications of eight quails each. The metabolizable energy levels were 2900 and 3000kcal of ME/kg of diet and the crude protein levels were 22, 24, 26 and 28%. The analyzed variables were weight gain (g), accumulated weight (g), feed consumption (g), feed:gain ratio (g/g). Performance responses were evaluated by linear and quadratic regression of the traits on crude protein levels. Higher weight gains from the following protein and metabolizable energy levels combinations: 28.0% PB and 2900 kcal EM/kg (first period); 25.7% CP and 3100kcal ME/kg (second period); 27.9% and 2900kcal ME/kg (third period); 24.8% PB and 3100kcal/kg (fourth period) and 23.1% CP and 2900kcal/kg (fifth period).

Estimativas de parâmetros genéticos de características reprodutivas de touros Nelore, de dois e três anos de idade

Heritabilities and genetic correlations between performance and reproductive traits were estimated using Multiple Trait Derivative-Free Restricted Maximum Likelihood methodology in 579 pasture-raised Nelore bulls that were 19 to 39 months of age. Traits were breeding soundness evaluation (BSE), scrotal circumference (SC), testicular consistency (TC), testicular volume (TV), testicular shape (TS), length and width of right and left testicles, and semen traits including motility (Mot), vigor (Vig), major (MD) sperm defects, minor (mD) sperm defects and total (TD) sperm defects. Heritability estimates were 0.46; 0.10; 0.08; 0.16; 0.09; 0.11 and 0.10 for TC, Mot, Vig, MD, mD, TD and BSE, respectively. Genetic correlations between SC and: body weight (BW), TV, Mot, Vig, mD, TD and BSE were 0.72; 0.99; 0.72; 0.60; -0.67; -0.12 and 0.64, respectively, showing favorable associations between SC and the other traits. Genetic correlations between BSE and: BW, TV, MD and TD were 0.19; 0.71; -0.47 and -0.58, respectively. Results suggest that selection for body weight in Nelore bulls should not hamper fertility, nor should selection for reproductive traits hamper growth.

Technical and economic evaluations of different genetic groups of yearling beef cattle males and of the feedlot production system

This experiment was carried out to evaluate technical and economic parameters for feedlot production system of 88 seven-month-old animals of three genetic groups (23 Charolais x Nellore, 26 Red Angus x Nellore, and 39 Aberdeen Angus x Nellore). Production traits (initial and slaughtering weights, number of days in feedlot, and total and daily weight gains) were recorded and costs were estimated using operational and economic concepts. The statistical model used to analyze the traits included the fix effect of genetic group and initial body weight as a covariate. No differences were observed among the genetic groups for slaughtering weight and daily weight gain. Number of days in feedlot was low for Charolais x Nellore (159 days), intermediate for Red Angus x Nellore (170 days), and high for Aberdeen Angus x Nellore (178 days) animals. Total, operational, and variable costs were 1.02; 0.85; and 0.89 US

Análise de custos de diferentes grupos genéticos de bovinos de corte terminados em confinamento

/day. Farmer profit was 0.01 US

Critérios de seleção para características de crescimento em bovinos da raça Nelore

/kg and profitability/month was 1.78%. Significant differences among the genetic groups were not observed for cost, income, gross and net margins, profit, and profitability.

Estimativas de parâmetros genéticos para características de desempenho de suínos em fase de crescimento e terminação

Data on feedlot performance of 149 steers were used to evaluate the economic efficiency of yearling Nellore, weaned Nellore, ½ Valdostana ½ Nellore, ½ Simmental ½ Nellore, ½ Braford ½ Brangus, ½ Braford ¼ Angus ¼ Nellore, Brangus, ½ Canchim ¼ Angus ¼ Nellore and ½ Canchim ¼ Simmental ¼ Nellore. Variable operational costs, kg of meat costs, and gross margin income were analyzed by ordinary least squares procedure including the effects of genetic groups and initial weight in the feedlot as a covariate. The means were compared by Duncan test (P<.05). The largest variable operational costs in the period, in US

Teor de metionina + cistina total para codornas de corte do grupo genético EV2 durante o período de crescimento

, were observed for ½ Canchim ¼ Simmental ¼ Nellore (160.8), weaned Nellore (158.7) and ½ Canchim ¼ Angus ¼ Nellore (155.1). The lowest kg of meat costs, in US

Análise de sensibilidade da margem bruta da receita e dos custos do confinamento de diferentes grupos genéticos

, were observed for yearling Nellore (0.79) and Brangus (0.82). The highest gross margin was obtained for yearling Nellore (94.6), followed by Brangus (71.5) and ½ Simmental ½ Nellore (46.6) The heaviest genetic groups in the beginning of the feed lot were confined for shorter periods and had the largest gross margins.