Ricardo Zambarda Vaz

Principal component analysis of breeding values for growth and reproductive traits and genetic association with adult size in beef cattle1

Principal component analysis was applied to evaluate the variability and relationships among univariate breeding values predicted for 9 weaning and yearling traits, as well as suggest functions of the traits that would promote a particular breeding objective. Phenotypic and pedigree information from 600,132 Nelore animals was used. Genetic parameters and breeding values were obtained from univariate analyses of birth to weaning weight gain; weaning to yearling weight gain; conformation, finishing precocity, and muscling scores at weaning and at yearling; and yearling scrotal circumference. The principal component mainly associated with maturity (precocious vs. late animals) was used as a pseudophenotype in bivariate analyses with either adult weight or adult height of cows. Direct heritability estimates ranging from 0.19 ± 0.01 to 0.41 ± 0.01 indicate that these 9 traits are all heritable to varying degrees. Correlations between the breeding values for the various traits ranged from 0.14 to 0.88. Principal component analysis was performed on the standardized breeding values. The first 3 principal components attained the Kaiser criterion, retaining 48.06%, 18.03%, and 12.97% of the total breeding value variance, respectively. The first component was characterized by positive coefficients for all traits. The second component contrasted weaning traits with yearling traits. The third component represented a contrast between late maturity animals (better for weight gain and conformation) and early maturity animals (better for finishing precocity, muscling, and scrotal circumference). Thus, the first 3 components represent 3 different potential selection criteria. Selecting for the first principal component would identify animals with positive breeding values for all studied traits. The second principal component may be used to identify animals with higher or lower maturation rates (precocity). Animals with negative values in the third principal component are regarded as early maturing. Genetic correlations between maturity (third principal component) with adult weight and adult height were 0.19 ± 0.02 and 0.32 ± 0.02, respectively. These results showed that the weaning and yearling bovine maturity is genetically associated with the adult size of the cows used in reproduction.

Pre-slaughtering factors related to bruises on cattle carcasses

The objective of the study was to determine the factors related to beef cattle carcass bruises. Handling, transportation and unloading data from cattle purchased by a slaughterhouse in southern Brazil were obtained to assess their associations with carcass bruising (occurrence or not) and the number of bruises per load. In total, 4338 carcasses from 142 loads of cattle purchased by the company were assessed. The females were cull cows and the males were steers. Independent variables studied included sex (females or males), loading facilities (good, regular or poor), cattle handling (good, regular or poor), transport time from the farm to the slaughterhouse (hours), hauling-truck types, truck animal-load density (kg/m2) and slaughterhouse unloading time (min). For both traits studied (carcasses bruised and number of bruises per load), all of the independent variables showed a significant (P 431 kg/m2) densities. In general, greater bruising was caused by longer transport and unloading times. Bruises were reduced by improving loading facilities from regular to good. Transportation in vehicles with higher load capacities (animal numbers) resulted in greater bruising. Therefore, special handling practices and personnel training measures should be undertaken to mitigate losses pre-slaughter, especially when handling female cattle, which are more vulnerable to developing carcass bruises, possibly due to higher cow reactivity.

Productivity and production efficiency of cows of different genetic groups submitted to cultivated pastures during pre or postpartum.

Avaliou-se atraves do desenvolvimento de vacas e bezerros ate o desmame aos 90 dias e tambem do desempenho reprodutivo desde a prenhez ate a desmama, a produtividade e a eficiencia de 94 vacas de corte dos grupos geneticos Charoles (CH), Nelore (NE), ½CH ½NE e ½NE ½CH submetidas aos seguintes sistemas de alimentacao: vacas mantidas exclusivamente em pastagem nativa (PN); vacas mantidas em pastagem cultivada (PC), composta por aveia (Avena sativa), azevem (Lollium multiflorum) e trevo vesiculoso (Trifolium vesiculosum) durante o periodo de 15 de julho a 15 de setembro e o restante do periodo experimental em pastagem natural (PCN); e vacas mantidas em pastagem cultivada durante o periodo de 15 de setembro a 15 de novembro, e o restante do periodo em pastagem nativa (PNC). As vacas mantida em PC produziram 22,6% a mais de bezerros do que as vacas mantidas exclusivamente em PN, bem como foram mais eficientes no indice de producao de bezerros (eficiencia dos rebanhos), com 57,0 vs 37,0 kg de bezerros/vaca mantida no rebanho. Na producao de kg de bezerros por vaca, as femeas mantidas em PC no pos-parto (69 kg) foram superiores (P 0,05), sendo estas superiores as puras na produtividade e eficiencia produtiva.

Amendoim forrageiro manejado com baixos resíduos de pastejo por ovinos

ABSTRACT This research aimed to study the productive behavior of perennial peanut (Arachis pintoi cv. Amarillo) under different grazing intensities by sheep in a rotation environment. The treatments consisted of four grazing intensity levels (very lenient - VL, lenient - L, moderate – M, and severe - S) represented by the residues 11.2; 8.4; 5.9 and 3.2cm, and allocated randomly with four replications. The variables studied in the pre-grazing and post-grazing were: forage mass, percentage of leaves and stems and leaf area index. At the end of the experiment, total accumulated forage mass, accumulation rate, and mass of missing forage were calculated. The data was submitted to a variance analysis and comparison to a Tukey’s test, with a 5% significance level. Grazing intensity was found to modify the composition of morphological components and the forage mass accumulated by peanuts; however, the leaf area index in pre-grazing remained constant. Perennial peanut should not be used under intensive grazing. Grazing intensity from moderate to very lenient provides greater mass of pre-grazing forage and total accumulated forage, combined with shorter intervals between grazing. Keywords: Arachis pintoi

Use of the correlation between input variables in estimating the risk of feedlot finishing of steers and young steers

The objective of this study was to evaluate the risk of feedlot finishing of steers (22.8 months) and young steers (15.2 months), using or not a correlation between the random input variables (data collected from 2004 to 2010) in the simulation of the Net Present Value (NPV) financial indicator. The animals were fed a diet containing roughage:concentrate ratio of 60:40 for 34 and 143 days, respectively, until they had reached a predetermined slaughter weight of 430 kg. For the NPV simulation, Latin Hypercube sampling was used, with 2000 interactions. The stochastic dominance analysis, test of differences between pairs of curves of cumulative distributions and sensitivity analysis were carried out. The NPV simulation using the correlation resulted in the best option for risk estimate. The confinement of young steers was the alternative of investment most viable than confinement of steers (NPV ≥ 0 of 80.4 vs. 62.3% in the simulation with correlation, respectively). Sensitivity analysis determined the following items had the greatest impact on the estimate of NPV: prices of fat and thin cattle, initial and final weights, diet costs, minimum rate of attractiveness and diet intake.