The objective of this study was to investigate the association of single nucleotide polymorphisms (SNPs) with birth weight, weight gain from birth to weaning and from weaning to yearling, yearling height and cow weight in Nelore cattle. Data from 5064 animals participating in the DeltaGen and PAINT breeding programs were used. The animals were genotyped with a panel of 777 962 SNPs (Illumina BovineHD BeadChip) and 412 993 SNPs remained after quality control analysis of the genomic data. A genome-wide association study was performed using a single-step methodology. The analyses were processed with the BLUPF90 family of programs. When applied to a genome-wide association studies, the single-step GBLUP methodology is an iterative process that estimates weights for the SNPs. The weights of SNPs were included in all analyses by iteratively applying the single-step GBLUP methodology and repeated twice so that the effect of the SNP and the effect of the animal were recalculated in order to increase the weight of SNPs with large effects and to reduce the weight of those with small effects. The genome-wide association results are reported based on the proportion of variance explained by windows of 50 adjacent SNPs. Considering the two iterations, only windows with an additive genetic variance >1.5% were presented in the results. Associations were observed with birth weight on BTA 14, with weight gain from birth to weaning on BTA 5 and 29, with weight gain from weaning to yearling on BTA 11, and with yearling height on BTA 8, showing the genes TMEM68 (transmembrane protein 8B) associated with birth weight and yearling height, XKR4 (XK, Kell blood group complex subunit-related family, member 4) associated with birth weight, NPR2 (natriuretic peptide receptor B) associated with yearling height, and REG3G (regenerating islet-derived 3-gamma) associated with weight gain from weaning to yearling. These genes play an important role in feed intake, weight gain and the regulation of skeletal growth.
-The objective of this work was to define the traits that should be included as breeding objectives for Nellore cattle, according to simulations with a bio-economic model for rearing systems. The economic values (EVs) of the traits were calculated as the differences between the profits due to an increased performance of 1% in each trait, with the others traits remaining constant. To determine the impact of each selection on the revenue system, two scenarios were simulated based on the traits being selected. In the first scenario, the adopted selection criteria were: weaning weight (WW), weaning rate (WR), yearling weight (YW), and mature cow weight (MCW). In the second scenario, the cumulative productivity (CP) of dams was used as an indirect evaluation of the performance of calves, with all the other traits included, except WW. In the first scenario, an EV of R$ 1.44 kg -1 was obtained for WW. In the second scenario, an EV of R$ 2.91 kg -1 was obtained for CP. The trait with the highest EV in both scenarios was WR, which enhanced the profits by R$ 3.21 for each 1% increased performance. The meat price paid to the producer is the factor with the greatest impact on the EVs of all examined traits.
The objective of this work was to evaluate the effects of supplementation with melengestrol acetate (MGA), after timed artificial insemination (TAI), on the conception rate of Nellore cows, according to cyclicity during the protocol, estrus expression between intravaginal device withdrawal and insemination, and diameter of the largest follicle at the time of insemination, in order to identify predictors of the use of MGA. Multiparous lactating cows (577) were subjected to a hormonal protocol for ovulation synchronization. On day -2 of the protocol, the animals were painted with a marker on the base of their tail. On day 0, they were evaluated for estrus expression; the preovulatory follicle diameter (POFD) was measured by ultrasonography, and the artificial insemination was performed. The animals were assigned to two experimental groups according to the supplementation or not with 0.50 mg MGA, between 13 and 18 days after TAI. Pregnancy diagnosis was performed using an ultrasound examination 35 days after TAI. A positive effect of the treatment with MGA on the conception rate occurred generally in animals in anestrus, irrespective of the estrus expression. For animals treated with MGA, only those with POFD greater than 14 mm showed better conception rates that the control group.
Dados de pesos à desmama ajustados para 205 dias (P205) e ao ano ajustados para 365 dias (P365), de animais da raça Nelore provenientes de 29 fazendas de diferentes estados brasileiros distribuídos entre as regiões Norte, Sudeste e Centro-Oeste, participantes do Programa de melhoramento genético da raça Nelore (Nelore Brasil), foram utilizados para avaliar a presença da interação genótipo-ambiente (IGA), bem como estimar as herdabilidades direta (P365 e P205) e materna (P205) pelo método de máxima verossimilhança restrita com auxílio do programa MTDFREML. O modelo estatístico utilizado incluiu efeitos fixos de grupo contemporâneo, idade da vaca ao parto (covariável) e efeitos aleatórios genéticos direto (P205 e P365) e materno (P205). As correlações genéticas estimadas para as características P205 e P365 em cada uma das regiões, Norte (R1), Sudeste (R2) e Centro-Oeste (R3), foram, para P205: 0,85±0,11 entre R1 e R2; 0,96±0,07 entre R1 e R3; e, 0,95±0,07 entre R2 e R3, e para P365: 0,72±0,09 entre R1 e R2; 0,83±0,07 entre R1 e R3; e 0,85±0,08 entre R2 e R3. Esses resultados indicam que, na desmama (P205), o efeito da IGA não foi observado, porém para o peso ao ano (P365), na combinação envolvendo as regiões Norte/Sudeste foi verificado efeito da IGA.
SUMMARY The objective of this study was to evaluate the effect of the genotype-environment interaction (GEI) for scrotal circumference traits measured at different ages, 365 (SC365), 450 (SC450) and 550 (SC550) days of age, and age at first calving (AFC) for Nellore animals raised in different regions of Brazil. For the evaluation, the herds were grouped in the following regions of the country: North, Southeast and Central-west, using information from 26,619, 28,730, 14,476, 15,397 for the traits SC365, SC450, SC550 and AFC respectively. Genetic parameters, as well as the assessment of GEI were performed using Bayesian inference, using the programs of the BLUPF90. The estimated heritabilities were: 0.465 ± 0.021, 0.500 ± 0.022, 0.492 ± 0.026, 0.117 ± 0.017 for SC365, SC450, SC550 and AFC respectively. The results obtained in the analysis, indicated that this interaction was not significant for SC at different ages (genetic correlation, rg> 0.8). For AFC, significant effect of GEI was observed for combinations involving the Northern region (rg<0.8), indicating that this interaction should be considered by the genetic evaluation programs in this region.
Resumo Com o objetivo de caracterizar a diversidade geoclimática da região Nordeste do Brasil e sua adequação à criação de bovinos de corte, foram avaliadas informações de altitude, precipitação, temperatura média anual, umidade relativa do ar e índice de temperatura e umidade de 94 municípios. Para a verificação da importância das variáveis supracitadas e melhor avaliação da divergência entre os estados, foi realizada uma análise multivariada dos dados. Utilizando dados padronizados foi realizada a análise de variáveis canônicas e a análise de agrupamento pelo método Unweighted Pair Group Method with Arithmetic Mean (UPGMA), utilizando os programas SAS e GENES. Os resultados mostraram que as duas primeiras variáveis canônicas explicaram mais 88% das variações entre os estados, sendo os municípios da Bahia e do Maranhão os que apresentaram maior divergência em relação aos demais. Como resultado da análise de agrupamento, observou-se a formação de dois grupos, sendo o menor grupo, com seis municípios, o que apresentou maior dissimilaridade com relação aos outros da região, mostrando que as variáveis estudadas foram eficazes em discriminar as cidades da região.
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