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)

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)

Estimates of direct and maternal genetic effects for weights from birth to 600 days of age in Nelore cattle

Estimates of direct and maternal variance and heritability for weights at each week (up to 280 days of age) and month of age (up to 600 days of age) in Zebu cattle are presented. More than one million records on 200 000 animals, weighed every 90 days from birth to 2 years of age, were available. Data were split according to week (data sets 1) or month (data sets 2) of age at recording, creating 54 and 21 data sets, respectively. The model of analysis included contemporary groups as fixed effects, and age of dam (linear and quadratic) and age of calf (linear) effects as covariables. Random effects fitted were additive direct and maternal genetic effects, and maternal permanent environmental effect. Direct heritability estimates decreased from 0.28 at birth, to 0.12-0.13 at about 150 days of age, stayed more or less constant at 0.14-0.16 until 270 days of age and increased with age after that, up to 0.25-0.26. Maternal heritability estimates increased from birth (0.01) to a peak of 0.14 for data sets 1 and 0.07-0.08 for data sets 2 at about 180-210 days of age, before decreasing slowly to 0.07 and 0.05, respectively, at 300 days, and then rapidly diminished after 300 days of age. Permanent environmental effects were 1.5 to four times higher than genetic maternal effects and showed a similar trend.

Estimates of covariance functions for growth from birth to 630 days of age in Nelore cattle

Weight records of Brazilian Nelore cattle, from birth to 630 d of age, recorded every 3 mo, were analyzed using random regression models. Independent variables were Legendre polynomials of age at recording. The model of analysis included contemporary groups as fixed effects and age of dam as a linear and quadratic covariable. Mean trends were modeled through a cubic regression on orthogonal polynomials of age. Up to four sets of random regression coefficients were fitted for animals' direct and maternal, additive genetic, and permanent environmental effects. Changes in measurement error variances with age were modeled through a variance function. Orders of polyno-mial fit from three to six were considered, resulting in up to 77 parameters to be estimated. Models fitting random regressions modeled the pattern of variances in the data adequately, with estimates similar to those from corresponding univariate analysis. Direct heritability estimates decreased after birth and tended to be lowest at ages at which maternal effect estimates tended to be highest. Maternal heritability estimates increased after birth to a peak around 110 to 120 d of age and decreased thereafter. Additive genetic direct correlation estimates between weights at standard ages (birth, weaning, yearling, and final weight) were moderate to high and maternal genetic and environmental correlations were consistently high. © 2001 American Society of Animal Science. All rights reserved.

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.

Genetic effects on preweaning weight gain of Nelore-Hereford calves according to different models and estimation methods

Additive and nonadditive genetic effects on preweaning weight gain (PWG) of a commercial crossbred population were estimated using different genetic models and estimation methods. The data set consisted of 103,445 records on purebred and crossbred Nelore-Hereford calves raised under pasture conditions on farms located in south, southeast, and middle west Brazilian regions. In addition to breed additive and dominance effects, the models including different epistasis covariables were tested. Models considering joint additive and environment (latitude) by genetic effects interactions were also applied. In a first step, analyses were carried out under animal models. In a second step, preadjusted records were analyzed using ordinary least squares (OLS) and ridge regression (RR). The results reinforced evidence that breed additive and dominance effects are not sufficient to explain the observed variability in preweaning traits of Bos taurus x Bos indicus calves, and that genotype x environment interaction plays an important role in the evaluation of crossbred calves. Data were ill-conditioned to estimate the effects of genotype x environment interactions. Models including these effects presented multicolinearity problems. In this case, RR seemed to be a powerful tool for obtaining more plausible and stable estimates. Estimated prediction error variances and variance inflation factors were drastically reduced, and many effects that were not significant under ordinary least squares became significant under RR. Predictions of PWG based on RR estimates were more acceptable from a biological perspective. In temperate and subtropical regions, calves with intermediate genetic compositions (close to 1/2 Nelore) exhibited greater predicted PWG. In the tropics, predicted PWG increased linearly as genotype got closer to Nelore. ©2006 American Society of Animal Science. All rights reserved.