Use of progeny testing in beef cattle: Prediction of genetic gain in a Nelore Cattle Breeding Program

Genetic gains predicted for selection, based on both individual performance and progeny testing, were compared to provide information to be used in implementation of progeny testing for a Nelore cattle breeding program. The prediction of genetic gain based on progeny testing was obtained from a formula, derived from methodology of Young and Weiler (J. Genetics 57: 329-338, 1960) for two-stage selection, which allows prediction of genetic gain per generation when the individuals under test have been pre-selected on the basis of their own performance. The application of this formula also allowed determination of the number of progeny per tested bull needed to maximize genetic gain, when the total number of tested progeny is limited.

Avaliação da silagem de milho das variedades granífera e forrageira no desempenho de bovinos das raças nelore e cachim em regime de confinamento

The experiment was carried out to evaluate corn grain and corn forage varieties productivity and nutritive value for silage comparing to the performance of Nellore and Canchim cattle in a feedlot. A completely randomized design was used with a 2 x 2 factorial arrangement based on two breeds (Nellore and Canchim) and two corn varieties (grain and forage). Harvest was made after 120 days sowing, when plants showed more than 2/3 of dry. leaves and grains were in dough stage. The silage was stored in a 400 tons. The experimental diet consisted of grain and forage corn silage, 7,2 liters of liquid yeast (1,5 kg of dry yeast/ head/day) and 1,1 kg of ground corn (1,0 kg of dry matter/head/day). The experiment duration was 110 days, with a 20 days adaptation period and 90 days for data collection. Animals were regularly weighted every 28 days. It was concluded that corn grain was more appropriate for silage than corn forage, and in the same stage it showed a higher dry matter content and a 41.3% higher grain yield, promoting higher weight gain and better feed/gain ratio in the feedlot beef cattle.

Degradabilidade ruminal do amido de silagem de milho, farelo de soja e sorgo grão, em bovinos da raça Nelore

Four Bos indicus (Nellore) ruminally-fistulated animals, averaging 36 months of age and 520 kg, were used in a randomized block design to study the ruminal degradability of starch in corn silage, soybean meal, and sorghum grain. The experimental diets consisted of two levels of concentrate (18 and 39%) plus corn silage. The concentrate ingredients used were soybean meal, cottonseed meal, corn grain, and sorghum grain. The degradation rate of sorghum grain increased 40.2% in diet 2 . The potential degradability of starch (PDS) was similar in the two diets. There was no difference between the two diets in the effective degradability of starch (EDS) in corn silage. There was a significant increase of 26.5% in the EDS of starch in sorghum grain with the increase of level of concentrate in the diet, and considering the lag time in the calculation. The starch level estimated in this study was lower than the values cited in the literature, probably due to different laboratory methods for determining the starch content in feedstuffs. Previous studies suggested using a minimum of 6 incubation intervals between 2 and 24 hours.

Degradabilidade ruminal da matéria seca e da fração protéica da silagem de milho, do farelo de soja e do sorgo grão, em bovinos da raça nelore. Comparação com os dados obtidos pelo CNCPS

The nylon bag in situ degradation thecnique was employed to compare the data of the CNCPS to the ruminal degradability of the dry matter and crude protein in corn silage, soybean meal and sorghum grain, in four rumen fistulated Nellore steers, averaging 36 months of age and 520 kg of liveweight. A randomized complete block experimental design was used, where animals constituted the blocks. Two levels of concentrate, 18 and 39 %, were used in the diets. The forage used in the diets was corn silage and the concentrate ingredients were: soybean meal, cottonseed meal, corn grain and sorghum grain. There was a reduction in the potentially by degradable fraction (B) of the dry matter(DM) of the corn silage and sorghum grain with an increase in the concentrate level of the diet; however, the degradation rate(c) of the silage was similar for the two diets and the sorghum grain showed an increase of 28.4 %. The B fraction of the DM from the soybean meal was not affected by the diet, but its rate (c) was reduced by 18.1 %. The same effect was observed for the rate(c) of crude protein(CP) of the soybean meal, with a reduction of 38.1 %. The values for the effective degradability of the two fractions were not affected by the diet when the lag time was not considered. When lag time was considered, the degradability values of the studied feeds were superior in both fractions.

Degradabilidade ruminai da fibra em detergente neutro e do nitrogênio insolúvel em detergente neutro da silagem de milho e do farelo de soja, em bovinos da raça nelore

The nylon bag in situ degradation thecnique was employed to study the ruminai degradability of the neutral detergent fiber and neutral detergent insoluble nitrogen of the corn silage and soybean meal in four rumen fistulated Nellore steers, averaging 36 months of age and 520 kg of liveweight. A randomized completelcs block experimental design was used, where the animals constituted the blocks. It was used diets with two levels of concentrate: 20 and 40%.The forage used in the diets was corn silage, and the concentrate ingredients were: soybean meal, cottonseed meal, corn grain and sorghum grain. The NIDN degradation rate of the corn silage and the soybean meal showed a decrease of 32,1% and of 46,0 % as a function of the higher concentrate level of the diet, but the effective and potential degradability of this fraction were not affected. Concerning to the NDF, the soluble fraction, potentially degradable and undegrable , were not affected by the increase on the diet concentrate level, but for the corn silage, there were 21,8% of reduction on the effective degradability of NDF. The use of lag time promoted higher degradability values for the studied fraction. The obtained values for some evaluated parameters, different from that assumed by CNCPS, showed the necessity of more data about brazilian used feeds, for model adjustments.

Fatores de correção do perímetro escrotal para efeitos de idade e peso ao sobreano de tourinhos nelore

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeitos Ambientais sobre Ganho de Peso no Período do Nascimento ao Desmame em Bovinos da Raça Nelore

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fatores de Correção para Ganho de Peso Médio Diário no Período do Nascimento ao Desmame em Bovinos da Raça Nelore

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Crescimento pré-natal do corpo e de alguns órgãos de Zebu mestiço coletados em matadouros de São Paulo

A total of 196 fetuses of crossbred Zebu between 106 to 246mm in length collected from a slaughterhouse in São Paulo, Brazil, and divided into groups of 10mm size differences intervals into 15 classes were measured and weighed. Liver, heart and lungs were also removed and weighed. In order to select the method of evaluation of growth several mathematical functions were applied. Among significant equations the monologarithmic function was selected. Furthermore, the fetuses in similar conditions of length and weight were compared with racially pure fetuses.

Efeitos da Seleção para Peso Pós-desmame sobre Medidas Corporais e Perímetro Escrotal de Machos Nelore de Sertãozinho (SP)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Estudo de modelo alternativo para estimação de componentes de (co)variância e predição de valores genéticos de características de crescimento em bovinos da raça Nelore

The objectives of this study were to estimate genetic parameters for non-standardized weights at nursing (PR120), at weaning (PR240), at yearling (PR365) and at post yearling (PR550), and to predict EPD's (expected progeny differences) for these traits using records from 29,769 Nellores. Covariance components and genetic parameters were estimated by mixed-model methodology, REML, using an animal model. Models for PR120, PR240, PR365 and PR455 included the random direct and maternal animal effects, the dam permanent environmental effect and the error. Fixed effects were contemporary group (CG) and age of cow at parturition (CIVP) and the covariate age of the calf at measuring. Two additional models for PR365, PR455 and PR550 analyses were used: the first included CG and CIVP, animal and maternal direct effect, residual and age of the calf (as covariate), and the second included CG and CIVP (as fixed effects), animal direct effect, residual and age of calf at measuring. Observed means±standard deviations were: 127±25kg (PR120); 191±34kg (PR240); 225±42kg (PR365); 266±51kg (PR455) and 310±56kg (PR550). From single-trait analyses, direct and maternal heritabilities for PR120, PR240, PR365 and PR455 were, respectively, .23 and .08; .19 and .10; .24 and .04; .30 and .04. Direct heritabilities were .39; .44 and .43, respectively, for PR365, PR455 and PR550. In the model without permanent effect, direct and maternal heritabilities for PR365, PR455 and PR550 were .25 and .08; .32 and .07; .38 and .03, respectively. When the estimates for standardized traits at the same period were compared, no differences in magnitude were found. Rank correlation had important changes when standardized and non-standardized traits were compared.

Avaliação clínica e hematológica em bezerros Nelore infectados experimentalmente com isolados de Babesia bigemina das regiões Sudeste, Nordeste e Norte do Brasil

A comparative study was made regarding the clinical and hematological alterations caused by isolates of Babesia bigemina from southeastern, northeastern and northern Brazil in experimentally infected Nelore calves. Eighteen calves between 7 and 9 months of age, without antibodies against Babesia sp and raised free from ticks, were used. Three animals were previously inoculated with 2.0×109 parasitic erythrocytes (PE) for each stabilate. The other 15 calves were subdivided into three groups, with five animals each, that were subinoculated with 1.0×1010 PE of the respective isolates. The clinical and hematological alterations were evaluated by the determination of parasitaemia, haemogram, plasmatic fibrinogen, reticulocyte count, descriptive analysis of the bone marrow and erythrocytic osmotic fragility, for 30 days, totalizing seven moments of observation. The follow-up of the immunological response by the indirect fluorescent antibody test was carried out daily until the 10th day after inoculation (DAI) and after that, on the 15th, 20th, 25th and 30th DAI. A mild clinical manifestation of the disease was observed. The laboratory findings revealed low levels of parasitaemia; decrease of the erythrogram values; absence of reticulocytes, initial decrease in the total count of leukocytes, neutrophils and lymphocytes with a posterior elevation of the number of these cells; hypercellularity of the erythrocytic series and decrease of the myeloid: erythroid relation which was more accentuated between the 8th and 12th DAI, and an increase of the erythrocytic osmotic fragility in the groups inoculated with the Southeast and Northeast isolates. None of the three isolates of B. bigemina gave rise to the clinical characteristic form of the disease, although they induced an humoral immune response.

Tendências genéticas para características relacionadas à velocidade de crescimento em bovinos nelore na região nordeste do brasil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Desenvolvimento morfolôgico dos ovários em embriões e fetos bovinos da raça Nelore

The morphologic events related to the prenatal development of the ovaries in 81 Nelore breed embryos and fetuses gathered in a local slaughterhouse, with age range from 26 to 240 days following fecundation were studied. The age of fetuses was estimated from measures taken in the cranium-caudal direction. The sex was identified from macroscopic observations and using Polymerase Chain Reaction (PCR) technique. For histology the gonads were fixed in Bourn's fluid for 24 hours and 5 μm thick section's were stained with hematoxylin-eosin. Formation of gonadal ridge and presence of germinal cells were found within it at 29 and 34 days, respectively. Oogonia and primordial follicles, unlike the growing follicles, exhibited significant differences in diameter in the various periods studied. Positive correlation (P<0.05) was found between the diameter of oogonia and their nucleus as well as between primordial and growing follicles with their oocytes and respective nuclei. The gonad was fully formed at 40 days. Primordial follicles, in the growing stage, and antral follicles first appeared, approximately at 95, 140, and 180 days, respectively. Despite the onset and duration of oogenesis being similar to that of taurine breeds, folliculogenesis initiates at an early stages in the Nelore breed.

Estimates of covariance functions for growth of Nelore cattle applying a parametric correlation structure to model within-animal correlations

A total of 20,065 weights recorded on 3016 Nelore animals were used to estimate covariance functions for growth from birth to 630 days of age, assuming a parametric correlation structure to model within-animal correlations. The model of analysis included fixed effects of contemporary groups and age of dam as quadratic covariable. Mean trends were taken into account by a cubic regression on orthogonal polynomials of animal age. Genetic effects of the animal and its dam and maternal permanent environmental effects were modelled by random regressions on Legendre polynomials of age at recording. Changes in direct permanent environmental effect variances were modelled by a polynomial variance function, together with a parametric correlation function to account for correlations between ages. Stationary and nonstationary models were used to model within-animal correlations between different ages. Residual variances were considered homogeneous or heterogeneous, with changes modelled by a step or polynomial function of age at recording. Based on Bayesian information criterion, a model with a cubic variance function combined with a nonstationary correlation function for permanent environmental effects, with 49 parameters to be estimated, fitted best. Modelling within-animal correlations through a parametric correlation structure can describe the variation pattern adequately. Moreover, the number of parameters to be estimated can be decreased substantially compared to a model fitting random regression on Legendre polynomial of age. © 2004 Elsevier B.V. All rights reserved.