V.M. Penna

Genetic association among scrotal circumference and female reproductive traits in Nellore

The objectives of this work were to estimate of genetic parameters for scrotal circumference (SC) at 12 (SC12, n = 652) and 18 (SC18, n = 607) months of age, age at first calving (AFC, n = 1,582), first (FCD, n = 1,582) and second (SCD, n = 644) calving dates and first calving interval (FCI, n = 644) in Nellore cattle. Parameters were estimated using REML methodology, with animal models and considering the relations among 15,648 animals. Heritability estimates from univariate analyses were .24±.10, .31±.10, .01±.03, .11±.05, .07±.08 and .10±.10, respectively, for SC12, SC18, AFC, FCD, SCD and FCI. These values were close to the estimates from bivariate analyses, except for the analysis including both SC (heritability estimates of .61 and .68, respectively, for SC12 and SC18). Genetic correlation estimates between SC12 and, respectively, AFC, FCD, SCD and FCI were ¾1.00, -.08, -.71, and -.37. In the same order, genetic correlation between SC18 and female reproductive traits were ¾1.00, .21, -.35 and -.44. The selection for SC12 would be more effective than selection for SC18 when trying to improve the reproductive traits of the females.

Interação genótipo-ambiente em algumas características produtivas de gado de corte no Brasil

The objective of this study was to measure the genotype-environment interaction (GEI) effect on some growth traits in Nellore cattle. Data from 2,896 records of pre-weaning (PW), 2,605 of weaning (WW) and 1,522 of post-yearling (YW) weights with a total of 9,911 pedigree animals from two farms of different regions of Minas Gerais State, South (farm I) and Northeast (farm II) were analyzed. Contemporary groups consider the effects of month-year of birth, sex, and herd. Only data from animals raised under pasture conditions were used. Covariance components were estimated by MTDFREML. Direct heritability obtained from bivariate analyses were 0.24, 0.16 and 0.17 (farm I) and 0.25, 0.24 and 0.17 (farm II) for PW, WW and YW, respectively. The ranking correlations between farms were 0.74, 0.76 and 0.51 and genetic correlations between farms were 0.96, 0.95 and 0.53 for PW, WW and YW, respectively. These results showed that there was no evidence of GEI up to weaning time but there was a significant effect of this interaction on the post-yearling weight. If selection criterion includes growth traits measured after weaning, regional evaluation should be recommended for bulls choice.

Breeding program evaluation for dual purpose zebu cattle

A deterministic approach was used to predict genetic gain and net present value for a breeding program in a dual-purpose zebu cattle population. The considered criterias were body weights, dairy and reproductive traits. High genetic gains and profit were obtained. More than 70% of genetic profit was net present value, justifying selection costs. The small proportion of recorded animals in relationship to the beneficial population of the improvement and the high economic values of traits could explain this profit.

Ajustamento para Heterogeneidade de Variância para Produção de Leite entre Rebanhos da Raça Holandesa no Brasil

Data of 36,755 first lactation of Holstein cows, daughters of 866 sires, distributed in different states from 1980 to 1993, were stratified in herds according to the phenotypic standard deviation of the milk yield adjusted for adult age, in three levels: low (11,713 lactations), medium (12,764 lactations) and high (12,278 lactations). The total milk production adjusted for adult age and adjusted for adult age and for 305 days of lactation, within each class, and the base 10 logarithm transformations, square root, standardization and the division by class phenotypic standard deviation were analyzed. The averages of milk yield, the genetic, residual, and phenotypic variance components increased with the increase of the class mean standard deviation. The heritability did not have the same behavior, the heritability estimates of the traits of the class with high standard deviation were similar to the heritability of traits of class with low standard deviation, and both were smaller than the class with medium standard deviation, although the component of addictive genetic variance has been higher. The used transformations did not correct the existing heterogeneity of variance among the classes. The heritabilities of the unchanged characteristics varied from .25 to .35.

Evaluation of alternative breeding programs for dual purpose Zebu cattle

Utilizando-se simulacao deterministica, foram avaliados seis esquemas de melhoramento, com diferentes grupos de informacoes: (1) somente caracteristicas de crescimento, (2) somente caracteristicas leiteiras, (3) caracteristicas de crescimento e reprodutivas, (4) caracteristicas leiteiras e reprodutivas, (5) caracteristicas de crescimento e leiteiras e (6) caracteristicas de crescimento, leiteiras e reprodutivas. Avaliaram-se tambem a resposta a variacao no uso de touros provados por meio do teste de progenie, a resposta sem a realizacao do teste de progenie no estrato de vacas de corte da populacao e a resposta a variacao no valor economico do peso ao abate. Em todos os esquemas avaliados, foram verificados altos ganhos geneticos e lucros decorrentes do programa. Os esquemas que consideraram as caracteristicas leiteiras foram mais eficientes pela selecao para maior producao de leite e menor peso de vaca adulta. As caracteristicas de fertilidade foram mais importantes para os esquemas de corte. A resposta economica a selecao foi maior com o aumento no uso de touros provados, embora nao proporcionalmente. A contribuicao das caracteristicas de corte para o lucro genetico somente superou a das leiteiras quando o valor economico do peso ao abate superou em 14 vezes o da producao de leite. Foi demonstrado nao haver necessidade da realizacao do teste de progenie com as vacas de corte para o sistema de dupla aptidao estudado.

Análise multivariada de resultados da ovulação múltipla seguida de transferência de embriões de doadoras zebuínas

Data on 1390 Zebu donors multiple ovulation followed by embryo transfer results were analyzed. The donors came from different regions of Brazil and belonged to Brahman (31), Gir (22), Guzera (68) and Nelore (411) breeds. The age of donors ranged from 1.5 to 19.5 years old. The first recovery data and consecutive recovery data were submitted to multivariate analysis. The estimated Pearson correlation coefficients were: 0.72 between total recovered structures (ER) and number of viable embryos (EV); 0.66 between ER and total of positive pregnant receptors (PP); 0.53 between ER and number of palpated corpora luteum; 0.89 between EV and PP; 0.33 between EV and CL and 0.30 between PP and CL. Relationships among inbreeding coefficient, age of donors to superovulation, stimulating drug, drug dosage, recovery number and number of executed insemination were also observed. Factor analysis indicated the following factors for consecutive recoveries: factor 1 - factors that reduce superovulation response, factor 2 - superovulation scheme according to characteristics of donors, factor 3 - success of superovulation scheme. For first recovery analysis the following factors were designated: factor 1 - optimum age for superovulation, factor 2 - superovulation scheme according to characteristics of donors, and factor 3 - alternative superovulation scheme. The analysis also indicated the results of superovulation are quite variable and that the age of donors to superovulation, inbreeding coefficient of donors, recovery number, drug dosage and number of inseminations have high effect on the results. The number of viable embryos and the correlation between number of viable embryos and total of positive pregnant receptors can be indicators of MOET success.

Desenvolvimento do software DRLinhagem para detecção de linhagens citoplasmáticas e avaliação de seu efeito sobre os pesos à desmama e ao ano de idade de animais Nelore no Centro-Oeste brasileiro

Records on 769,925 Nelore animals born from 1965 to 2000, in 30 regions of Brazil were used as base data to develop a flexible a ease use computational program for identifying maternal base lines in herds, allowing filter by country, state, region and herd. The Center-West region was selected for a detailed study of cytoplasmatic lines on weaning and yearling weights of Nelore animals. The estimated variance components for citoplasmatic lines were .58 x 10-3 and .80 x 10-.8 for weaning and yearling weights, respectively, and accounted for 1.00x10-5 and 9.90x10-6 of total weights variance, respectively. The direct additive component accounts for 11 and 12% of the total phenotypic variance of weaning and yearling weights.