Estudo da interação genótipo × ambiente sobre características de crescimento de bovinos de corte utilizando-se inferência bayesiana

The objective of this study was to evaluate the genotype x environment interaction for weaning and yearling weights, daily weight gain from weaning to 12 months of age and the growth performance in Canchim (5/8 Charolais + 3/8 Zebu) beef cattle estimated by a principal components analysis including those three traits. The environment was defined by season of birth (first and second semesters of the year). Genetic parameters were estimated by bayesian method with the Gibbs sampler using bivariate analyses (considering the trait in each of the two seasons as a different one) and models that included the fixed effects of year and month of birth, sex and age of cow (linear and quadratic) and the random effects of animal and residual. The results suggested that genetic evaluation and selection in Canchim beef cattle for the traits studied should consider the genotype and season of birth interaction.

New Stylosanthes guianensis for tropical grasslands

Hybrid stylos (Stylosanthes guianensis var. vulgaris x var. pauciflora) with durable, quantitative resistance to anthracnose, mid-season harvest maturity date (early-July), high DM and seed yields have been selected at the Embrapa Beef Cattle Research Center, Campo Grande, Brazil. The hybrids displayed improved forage traits in Brazil, the native habitat and major center of diversity of the species and its pathogen, as well as in vastly different ecosystems. Dry forage yields and anthracnose resistance of superior selections and their composites were equal, in some instances, significantly better, than those of cv. Mineir (a) over tildeo in multilocational trials situated in the Cerrados from lat. 6degrees S to lat. 20degrees S. Selected hybrids performed well in comparison with the highly successful CIAT 184 (cv.Reyan II) on Hainan Island, China. Composites have also shown good promise in seed multiplication plots in Queensland, Australia. A positive attribute of composite hybrids is their great genetic diversity in contrast to pure-line cultivars with a relatively narrow genetic base. These truly tropical forms of stylo are best adapted to regions with >1500mm average annual rainfall.

Territorial hypothesis predicts the trade-off between reproductive opportunities and parental care in three species of damselfishes (Pomacentridae: Actinopterygii)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Modelos lineares generalizados mistos na avaliação genética da prenhez precoce na raça Nelore

This study aimed to use the generalized linear models with probit and logit link function to evaluate early pregnancy, and to observe the effects on genetic variability and on sire selection when different ages are adopted in the definition of this trait. Early pregnancy was studied at 15 (EP15), and 21 (EP21) months. The analysis was done in R software. Pearson correlations (PC), between genetic predicted values and percentage of bulls in common considering only 10% of bulls with higher genetic values (TOP 10), between classification by logit and probit models and in each model among EP15 and EP21, were calculated. The heritability for EP15 and EP21 were close between models, except for EP15 using probit link function. PC and TOP10 among models were high. The Akaike and Bayesian criteria reported was similar between models. TOP10, considering the same model, among EP15-EP21 were moderated between EP15-EP21.

Estimación de la heredabilidad del intervalo de partos en bovinos cruzados

Objetive. To estimate the heritability of interval calving in crossbred cattle. Materials and methods. Information from database of La Leyenda farm, in the municipality of Caucasia (Antioquia) was used. A single-trait animal model was used, that included genetic group, year of birth, season of birth and the number of calvings as fixed effects and the additive direct genetic, permanent environmental and residual as random effects. Results. The heritability estimated was 0.15 +/- 0.07 and the phenotypic mean was 544 +/- 97 days. Conclusions. The heritability for the interval between calvings was low, indicating that little genetic progress can be achieved by selecting for this characteristic.

Meta-análise de parâmetros genéticos relacionados ao consumo alimentar residual e a suas características componentes em bovinos

The objective of this work was to estimate, by meta-analysis, the heritability (h(2)) and the genetic (r(g)) and phenotypic (r(f)) correlations of residual feed intake (RFI), and of its component traits in beef cattle from 19 breeds or genetic groups. Twenty-two scientific papers published from 1963 to 2011, from eight countries, totaling 52,637 cattle of ages from 28 days up to slaughter, were evaluated. The estimates of RFI, dry matter intake (DMI), average daily gain (ADG) and metabolic weight (BW0.75) were weighted by the inverse of sample variance. The variation between studies of h(2) for each trait was analyzed by weighted least squares. The effects of sex, country and breed were significant for h(2) of RFI, explaining 67% of variation between studies. For DMI, country and breed effects were significant and explained 96% of variation. Pooled estimates of h(2) were: 0.255+/-0.008, 0.278+/-0.012, 0.321+/-0.015, and 0.397+/-0.032 for RFI, DMI, ADG and BW0.75, respectively. Pooled estimates of genetic and phenotypic correlations were low between RFI and ADG and between RFI and BW0.75 (from -0.021+/-0.034 to 0.025+/-0.035), and moderate between RFI and DMI (0.636+/-0.035 and 0.698+/-0.041) and between DMI, ADG and BW0.75 (0.441+/-0.062 to 0.688+/-0.032). The trait RFI has lower heritability estimates than its components.

Epidemiologia e quadro clínico do botulismo epizoótico dos bovinos no Estado de São Paulo

In order to investigate epidemiological and clinical aspects of beef cattle mortalities caused by botulism, a syndrome popularly known as doença da vaca caída, studies were carried out in 32 naturally affected 4 to 9 year old cows, 27 belonging to the Nellore breed and 5 to crossbred Nellore, all from 27 farms located in municipalities near Botucatu, State of São Paulo. The epidemiological and clinical features were based, respectively, on the farm and herd managements, and on the general physical examination of the cows. Mouse bioassay and complement microfixation tests were performed to detect the presence of botulinum toxins in liver samples. The results showed that the disease occurs in beef cattle of range breeding systems, reared under inadequate mineral nutrition and deficient health management. Pregnant and milking cows represented the group at risk, and the incidence was higher during the rainy season (December to March), with morbidity and mortality rates of 3,2 ± 3,6%. Clinical examination revealed cows with no alterations of vital signs, behavior, visual and auditory acuities and skin sensation; but revealed ruminal hypomotility, anorexia, dehydration, flaccid para or tetraparesis with permanent recumbency, and a paretic or paralytic tongue. The diagnosis of botulism, involving type C and D toxins, was consistent with the epidemiological and clinical findings.

Influência de fatores de meio sobre pesos de animais da raça Canchim

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estimativas de parâmetros genéticos e proposição de critérios de seleção para pesos na raça Canchim

The objectives of this study were to obtain heritability and genetic, phenotypic and environmental correlation estimates for birth (B), weaning (WW), yearling (YW) and 18 - (EW) and 24 - month (TW) weights, and to propose selection criteria for body weight in Canchim cattle. The data were analyzed by the least-squares method with models that included the fixed effects of herd, year and month of birth, sex of calf and age of cow at calving, and the random effects of sire within herd. The heritability estimates obtained were equal to 0.36 0.06 (BW), 0.47 0.06 (WW), 0.53 0.07 (YW), 0.54 0.08 (EW) and 0.27 0.06 (TW). The genetic correlations were equal to 0.51 (BW and WW), 0.36 (BW and YW), 0.14 (BW and EW), 0.00 (BW and TW), 0.92 (WW and YW), 0.77 (WW and EW), 0.75 (WW and TW), 0.94 (YW and EW), 0.86 (YW and TW) and 0.85 (EW and TW). The phenotypic correlations ranged from 0.19 to 0.72, and the environmental correlations from 0.11 to 0.61. The results showed that, in general, mass selection for weight will result in genetic progress, selection for weight at any age will result in correlated changes at other ages, and EW and TW are good selection criteria for increasing weight in the Canchim breed.

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.

Estimativas de parâmetros genéticos e fenotípicos para características de crescimento até a desmama em bovinos da raça Canchim

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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)

Comparação de sistemas de avaliação de dietas para bovinos no modelo de produção intensiva de carne. Confinamento de tourinhos jovens

Thirty 3/4 Canchim + 1/4 Nelore young bulls with 417 kg of body weight and 15 months of age, were confined during 84 days. The animals were fed with diets composed with corn silage, corn grain, cottonseed meal, soybean meal, whole soybean and mineral mix, adjusted in agreement with the recommendations of the Metabolizable Protein System (MP), Cornell Net Carbohydrate and Protein System (CNCPS) and Intestine Digestible Protein System (PDI), for predicted body weight gain of 1.3 kg/head/day. The daily body weight gain did not differ among treatments CNCPS, MP and PDI, with 1.51; 1.48; and 1.13 kg/head, respectively. The economic analysis revealed net profit of R$116.25; R$148.30; and R$108.51/head for CNCPS, MP and PDI systems, respectively. The diets adjusted by CNCPS and MP systems provided superior animal performance than that expected, while the diet adjusted by PDI system did not allow the predicted body weight gain.

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.

Acute reduction in serum progesterone concentrations after feed intake in dairy cows

This study tested the hypothesis that high feed consumption will acutely decrease circulating progesterone concentrations. In the first experiment, a Latin Square design was used to test whether feeding pattern would alter circulating progesterone in pregnant lactating Holstein cows (n = 12). Feed was removed for 12 h before the experiment and cows were then either fed 100% of the total mixed ration (TMR), 50% of TMR every 12 h, 25% of TMR every 6 h, or left unfed for an additional 12 h. Blood samples were taken every hour for 24 h. Provision of 100 or 50% of TMR decreased circulating progesterone by 1 h after feeding and progesterone remained depressed until 8-9 h after feeding. Feeding 25% of TMR did not reduce circulating progesterone concentrations. Experiment 2 used a crossover design to measure the effect of acute feeding on circulating progesterone and LH concentrations during delivery of a constant amount of exogenous progesterone (Eazi-Breed CIDRs) in lactating Holstein cows (n = 8) and nonpregnant dry Holstein cows (n = 6). Blood samples were taken every 15 min for 8 h. There was no change in serum progesterone during the 8 h treatment period in unfed cows; however, feeding decreased (P < 0.05) circulating progesterone between 2 and 6 h after feeding. In lactating cows, feeding increased mean LH (P < 0.05). There were more LH pulses (P = 0.01) in lactating than nonlactating cows. Thus, acute feeding reduced circulating progesterone in pregnant lactating cows apparently due to an increase in progesterone metabolism. Interestingly, feeding multiple smaller meals eliminated the acute effect of feeding on circulating progesterone. © 2003 Published by Elsevier B.V.