Programa de Pós-graduação em Zootecnia
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Item Estudo genético-quantitativo de características de crescimento, reprodução, carcaça e escores visuais em um rebanho nelore sob seleção para precocidade sexual(Universidade Federal de Goiás, 2017-02-23) Brunes, Ludmilla Costa; Rey, Fernando Sebastian Baldi; http://lattes.cnpq.br/2142265309634106; Costa, Marcos Fernando Oliveira e; http://lattes.cnpq.br/9680699222245462; Magnabosco, Cláudio Ulhoa; http://lattes.cnpq.br/1852112832119187; Magnabosco, Cláudio Ulhoa; http://lattes.cnpq.br/1852112832119187; Lobo, Raysildo Barbosa; Mamede, Mariana Marcia SantosThe reproductive efficiency in cattle herds, as well as the anticipation of puberty, has positive effects on zootechnical indexes and on the profitability of production systems. Thus, the aim of this study was to estimate the genetic parameters and the genetic and phenotypic trends for growth, carcass, and reproductive traits in a Nellore cattle herd under selection for sexual precocity, given age at first conception and age at first calving as selection criterion. Furthermore, this study also aimed to evaluate, using multivariate analyzes, which traits, among growth, carcass and visual scores, better discern early pregnancy. Genetic parameters were estimated for birth weight (BW), weight at 120 (W120), 210 (W210), 365 (W365) and 450 (W450) days of age, average daily gain pre-weaning and post-weaning (ADGPRE e ADGPOS), rib eye area (REA), backfat thickness (BF), rump fat thickness (RF), marbling (MAR), hot carcass weight (HCW), weight of edible portion (WEP), scrotal circumference at 365 (SC365) and 450 (SC450) days of age, gestation length (LG), days open (DO), calving interval (CI), real fertility (RF), cumulative productivity (CP), relation to weaning (RW), age at first conception (AFCo) and age at first calving (AFCa). Data were provided by Vera Cruz Ranch and the National Association of Breeders and Researchers (ANCP). The covariance components were estimated using the Restricted Maximum Likelihood method, available on BLUPF90 package, in univariate and bivariate analyzes using animal model. The heritability estimated for BW (0.39), W120 (0.32), W210 (0.31), W365 (0.33), W450 (0.34), ADGPRE (0.23), ADGPOS (0.27), REA (0.39), BF (0.34), RF (0.34), MAR (0.38), HCW (0.39), WEP (0.39), SC365 (0.33), SC450 (0.33), LG (0.23), DO (0.34), CI (0.23), RF (0.21), CP (0.25), RW (0.26), AFCo (0.21) and AFCa (0.24) indicated the possibility of genetic selection. The maternal heritability estimated for BW (0.06), W120 (0.08), W210 (0.07), W365 (0.05), W450 (0.11), ADGPRE (0.12), ADGPOS (0.08), SC365 (0.07) and SC450 (0.03) indicated genetic effects of the dam on the progeny performance, until the post-weaning phase, for growth traits. The genetic correlations estimated within growth traits, between growth and carcass traits, within carcass traits and reproductive trait were favorable and of moderate magnitude. The traits that indicate sexual precocity showed genetic correlation coefficients ranging from -0.51 to -0.15, -0.62 to -0.33 and -0.61 to 0.14, between growth, carcass and reproductive traits, respectively. Genetic correlation coefficients were, in most cases, favorable. The genetic trends obtained showed, in general, the effectiveness of the adopted selection criteria with satisfactory genetic gains. Selection for sexual precocity, based on age at first conception, shall promote opposite direction genetic changes on growth, carcass and reproductive traits, which is the desirable effect. Birth weight, fat thickness, bone structure, musculature, rib depth, tail and rump insertion were the traits that presented greater discrimination power for early pregnancy. Thus, these traits can be used as such management targeting criteria and decision-making practices, in order to enable animals to express early pregnancy, guiding the breeders in selecting females for sexual precocity.Item Associação e seleção genômica para eficiência alimentar em bovinos Nelore(Universidade Federal de Goiás, 2021-02-22) Brunes, Ludmilla Costa; Rey, Fernando Sebastian Baldi; http://lattes.cnpq.br/2142265309634106; Lopes, Fernando Brito; http://lattes.cnpq.br/1399785191420919; Magnabosco, Cláudio Ulhoa; http://lattes.cnpq.br/1852112832119187; Magnabosco, Cláudio Ulhoa; Mascioli, Arthur dos Santos; Carmo, Adriana Santana do; Coelho, Alexandre Siqueira Quedes; Costa, Marcos Fernando Oliveira eThe aim of this study was to estimate genetic parameters for feed efficiency, growth, reproductive and carcass traits in commercial Nelore cattle herds, and the correlated response between them. It was also aimed perform a study of genomic selection evaluating prediction methods, validation approaches and pseudo-phenotypes, and conduct a weighted single-step genome-wide association study and an enrichment analysis for feed efficiency of feed efficiency related traits. Residual feed intake (RFI), dry matter intake (DMI), feed conversion ratio (FCR), feed efficiency (FE), residual live weight gain (RG), residual intake and live weight gain (RIG), birth weight (BW), weight at 120 (W120), 240 (W240), 365 (W365), and 450 (W450) days of age, scrotal circumference at 365 (SC365) and 450 (SC450) days of age, rib eye area (REA), backfat thickness (BF) and rump fat thickness (RF) were evaluated. The growth, reproductive and carcass traits records from 15,639 Nelore cattle were used. Data from feed efficiency tests carried out between 2011 and 2018, with phenotypic and genotypic information of 4,329 and 3,594 animals, respectively, were considered. The genetic parameters were estimated in a single step approach (ssGBLUP). Six prediction methods of genomic breeding values (GEBVs) were used: ssGBLUP, Bayes A, Bayes B, Bayes Cπ, BLASSO, and Bayes R. Three validation approaches were used: 1) random: the data set was randomly divided into ten subsets and the validation was done in each subset at a time; 2) age: the population was divided into training and validation set based on the year of birth, with the first group consisting of animals born between 2010 and 2016 and the second group born in 2017; 3) genetic breeding value (EBV) accuracy: were divided into two groups, with animals with accuracy above 0.45 considered as the training population, and below 0.45 the validation set. We checked the accuracy and bias of GEBV. The percentage of variance explained by windows of 10 adjacent SNPs was used to identify regions that explained more than 0.5% of the additive genetic variance on each trait. The feed efficiency related traits showed low to moderate heritabilities, ranging from 0.07 to 0.20. Feed efficiency related traits showed low genetic correlations with growth (-0.19 to 0.24), reproductive (-0.24 to 0.27) and carcass (-0.17 to 0.27) traits, except for growth with DMI (0.32 to 0.56) and FE (-0.40). The results showed that the prediction ability were similar between the prediction methods. The low heritability obtained, mainly for FE (0.07±0.03) and FCR (0.09±0.03), limited the GEBVs accuracy, which ranged from low to moderate. The regression coefficient estimates were close to 1, and similar between the prediction methods, validation approaches, and pseudophenotypes. On average and despite low variation (0.0331), the random cross-validation presented the most accurate predictions, ranging from 0.07 to 0.037, than EBV accuracy and age. The prediction ability was higher for phenotype adjusted for fixed effects than for EBV and EBV deregressed (30.0 and 34.3%, respectively). Enrichment analysis by The Database for Annotation, Visualization and Integrated Discovery (DAVID) revealed several functional vias such as neuropeptide signaling pathway (GO:0007218), negative regulation of canonical Wnt signaling pathway (GO:0090090), detection of chemical stimulus involved in sensory perception of bitter taste (GO:0001580), bitter taste receptor activity (GO:0033038), neuropeptide hormone activity (GO:0005184), bile secretion (bta04976), taste transduction (bta0742), and glucagon signaling pathway (bta04922). The selection to improve growth, reproductive and carcass traits would not change RFI, RG, and RIG. On the other hand, DMI, FE and FCR may lead to an increase in body weight, in addition to the selection for FCR may lead to a reduction in carcass yield. The genetic background of feed efficiency related traits are different, which would lead to different genetic responses. The choice of the most adequate selection criterion depends on the production system and goals. Genomic prediction methods can provide a reliable estimate of genomic breeding values for RFI, DMI, RG and RGI, traits that may have higher genetic gain and selection viability than FE and FCR. Enrichment analyzes showed genes associated with in insulin, leptin, glucose, protein and lipid metabolism, energy balance, heat and oxidative stress, zinc finger system, bile secretion, satiety, feed behavior, salivation, digestion and absorption of nutrients. The identification of these genomic regions and their respective genes provide information about genetic basis and biologic regulation for Nelore feed efficiency related traits.Item Parâmetros genéticos para características produtivas e de eficiência alimentar em bovinos Guzerá(Universidade Federal de Goiás, 2021-02-27) Pereira, Letícia Silva; Rey, Fernando Sebastian Baldi; http://lattes.cnpq.br/2142265309634106/; Carmo, Adriana Santana do; http://lattes.cnpq.br/0782572407995106/; Magnabosco, Cláudio Ulhoa; http://lattes.cnpq.br/1852112832119187; Magnabosco, Cláudio Ulhoa; Mascioli, Arthur dos Santos; Faria, Carina Ubirajara deThe Guzerat breed makes a great contribution to Brazilian livestock due to its rusticity and survival in the tropics, in addition to presenting favorable production rates regarding growth, fertility and feed efficiency. These characteristics are important criteria in determining the zootechnical and bioeconomic indexes within the production system. However, it is essential to understand the behavior of these characteristics, especially the residual food consumption, which has been used as a parameter for identifying animals that are efficient in the use of food, given that there is still little work in the literature on the Guzerat breed regarding the impact of selection for residual food consumption on the performance of characteristics of economic importance. The characteristics evaluated were weight at 120 (W120), 210 (W210), 365 (W365), and 450 (W450) days of age, scrotal circumference at 365 (SC365) and 450 (SC450) days of age, rib eye area (REA), backfat thickness (BF), rump fat thickness (RF), residual feed intake (RFI) and dry matter intake (DMI). The estimation of genetic parameters was performed by the method of maximum restricted likelihood (REML), under animal model in uni, bi and multi trait analyzes, in order to determine the genetic and phenotypic associations between these characteristics, and consequently the genetic planning and the indices selection without causing antagonisms in both characteristics. Heritability for growth characteristics, P120, P210, P365, P450, PE365 showed low to moderate coefficients in the three analyzes, uni (0.17, 0.21, 0.32, 0.39), bi (0.18, 0.22, 0.33, 0.39) and multi (0.34, 0.38, 0.35, 0.39), respectively. The carcass-related characteristics showed low to moderate heritability, AOL (0.24 to 0.27), EG (0.09 to 0.10) and EGP8 (0.29 to 0.31), whereas the characteristics of efficiency showed low coefficient of heritability varying from 0.14 to 0.23. CAR showed low genetic correlations with characteristics of growth (-0.07 to 0.22), reproduction (0.03 to 0.05) and carcass (-0.35 to 0.16), with the exception of CMS (0.42 to 0.46). In general, heritability and genetic correlations expressed considerable genetic variability and significant genetic gains can be obtained through selection for feeding efficiency, growth, reproduction and carcass characteristics in the Guzerat breed, and can be included simultaneously in selection programs, without causing genetic damage. or economic and thus promote greater genetic progress of the herds.Item Estudo genético quantitativo de características morfológicas, produtivas, reprodutivas e de carcaça em bovinos nelore(Universidade Federal de Goiás, 2021-02-23) Soares, Byanka Bueno; Rey, Fernando Sebastian Baldi; http://lattes.cnpq.br/2142265309634106; Carmo, Adriana Santana do; http://lattes.cnpq.br/0782572407995106; Magnabosco, Cláudio Ulhoa; http://lattes.cnpq.br/1852112832119187; Magnabosco, Cláudio Ulhoa; Mascioli, Arthur dos Santos; Melo, Leonardo de França eThe aim of this study was to estimate the genetic parameters of functional biotype indicator traits through the MERCOS methodology as well as the relationship between these and performance, carcass, and reproductive traits, in Nellore cattle using Bayesian Inference. The data set used contained information on 12,060 Nellore cattle born between 2001 and 2020, provided by HoRa Hofig Ramos. Visual scores data set from 4,175 Nellore cattle were used, such as muscling (M), physical structure (PS), racial (R), conformation (C), navel (N), and sacrum bone (SAC). Besides, body weights at 120 (W120), 210 (W210), 365 (W365), and 450 (W450) days of age, rib eye area (REA), backfat thickness (BF), rump fat thickness (RF), scrotal circumference at 365 (SC365) and 450 (SC450) days of age, stayability (STAY), probability of precocious calving (PPC) and age at first calving (AFC). The genealogy information used to compose the kinship matrix was provided by the National Association of Breeders and Researchers. Bi-trait Bayesian analyzes were performed using a linear-threshold model to combine linear and categorical traits, or threshold-threshold, when both traits analyzed, were categorical. The heritability estimates obtained are very wide, varying from low to high magnitude: 0.21; 0.28; 0.25; 0.25; 0.15; 0.18; 0.27; 0.28; 0.34; 0.44; 0.42; 0.46; 0.46; 0.50; 0.53; 0.38; 0.54 and 0.10 for M, BS, R, C, N, SAC, W120, W210, W365, W450, REA, BF, RF, SC365, SC450, STAY, PPC and AFC, respectively. These results indicate genetic selection feasibility and obtaining genetic gains, mainly for growth, carcass, scrotal circumference, STAY, PPC and visual scores as muscling, physical structure, racial and conformation. Still, genetic selection for visual scores is feasible. The maternal heritability estimates for W120 and W210 were: 0.16 and 0.13, respectively, indicating dam genetic effects on the progenies' performance until the weaning, for growth traits. The genetic correlations between visual scores were positive and from moderate to high, ranging from 0.25 to 0.89, except for the estimates obtained between visual scores N and SAC. The genetic correlations between visual scores and growth traits were, in general, moderate to high, except for R with W365 and W450, C with W210 and W450, O with W120, W210, and W450, and SAC with W210, W365, and W450 that were low. The genetic correlations between visual scores and carcass traits were, in general, low, except for REA with PS and SAC, which were moderate. The genetic correlations between visual scores and reproduction traits were generally low, except for M with PPC, PS with STAY, R with SC450, C with SC365, SC450, STAY and AFC, N with STAY and AFC, and SAC with SC365, STAY, and AFC, which were moderate. Estimates of genetic correlation indicate that direct selection for visual score traits may influence body weight and vice versa, and these responses are favorable. Even so, higher genetic gain for visual scores is expected if the selection is carried out directly for them, than selection for growth, reproduction, or carcass traits. However, selection for W365 and W450 may result in higher genetic gains in M and selection for REA in SAC, than direct selection for these traits. The selection of animals with higher scores, mainly for M, PS, and C scores can be used as selection criteria to get genetic gain for growth, sexual precocity, and fertility in Nellore cattle.