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In this study, we detected signatures of selection in Hanwoo and Angus beef cattle using allele frequency and haplotype-based methods based on imputed whole genome sequence variants. Our dataset included 13,202 Angus animals with 10,057,633 imputed SNPs and 10,437 Hanwoo animals with 13,241,550 imputed SNPs. The dataset was subset down to 6,873,624 SNPs in common between the two populations to identify within population (runs of homozygosity, extended haplotype homozygosity) and between population signals of selection (allele fixation index, extended haplotype homozygosity). Assuming these selection signals were complementary to each other, they were combined into a decorrelated composite of multiple signals to identify regions under selection for each of the breeds. 27 genomic regions spanning 25.15 Mb and harboring 360 genes were identified in Angus on chromosomes 1,3, 4, 5, 6, 7, 8, 12, 13, 14, 16, 20, 21 and 28. Similarly, in Hanwoo, 59 genes and 17 genomic regions spanning 5.21 Mb on chromosomes 2, 4, 5, 6, 7, 8, 9, 10, 13, 17, 20 and 24 were identified. Apart from a small region on chromosome 13, there was no major overlap of selection signals between the two breeds reflecting their largely different selection histories, environmental challenges, breeding objectives and breed characteristics. Positional candidate genes identified in selected genomic regions in Angus have been previously associated with growth, immunity, reproductive development, feed efficiency and adaptation to environment while the candidate genes identified in Hanwoo included important genes regulating meat quality, fat deposition, cholesterol metabolism, lipid synthesis, neuronal development, and olfactory reception. [ABSTRACT FROM AUTHOR]

Background: Carcass weight (HCW) and marbling (MARB) are critical for meat quality and market value in beef cattle. In composite breeds like Brangus, which meld the genetics of Angus and Brahman, SNP-based analyses have illuminated some genetic influences on these traits, but they fall short in fully capturing the nuanced effects of breed of origin alleles (BOA) on these traits. Focus on the impacts of BOA on phenotypic features within Brangus populations can result in a more profound understanding of the specific influences of Angus and Brahman genetics. Moreover, the consideration of BOA becomes particularly significant when evaluating dominance effects contributing to heterosis in crossbred populations. BOA provides a more comprehensive measure of heterosis due to its ability to differentiate the distinct genetic contributions originating from each parent breed. This detailed understanding of genetic effects is essential for making informed breeding decisions to optimize the benefits of heterosis in composite breeds like Brangus. Objective: This study aims to identify quantitative trait loci (QTL) influencing HCW and MARB by utilizing SNP and BOA information, incorporating additive, dominance, and overdominance effects within a multi-generational Brangus commercial herd. Methods: We analyzed phenotypic data from 1,066 genotyped Brangus steers. BOA inference was performed using LAMP-LD software using Angus and Brahman reference sets. SNP-based and BOA-based GWAS were then conducted considering additive, dominance, and overdominance models. Results: The study identified numerous QTLs for HCW and MARB. A notable QTL for HCW was associated to the SGCB gene, pivotal for muscle growth, and was identified solely in the BOA GWAS. Several BOA GWAS QTLs exhibited a dominance effect underscoring their importance in estimating heterosis. Conclusions: Our findings demonstrate that SNP-based methods may not detect all genetic variation affecting economically important traits in composite breeds. BOA inclusion in genomic evaluations is crucial for identifying genetic regions contributing to trait variation and for understanding the dominance value underpinning heterosis. By considering BOA, we gain a deeper understanding of genetic interactions and heterosis, which is integral to advancing breeding programs. The incorporation of BOA is recommended for comprehensive genomic evaluations to optimize trait improvements in crossbred cattle populations. [ABSTRACT FROM AUTHOR]

This study investigates the effects of varying energy levels in diets on Black Angus steers, focusing on growth performance, muscle composition, rumen microbial community, and their interrelationships. Twenty-seven Black Angus steers, aged approximately 22 months and weighing 520 ± 40 kilograms, were randomly divided into three groups: low-energy (LE), medium-energy (ME), and high-energy (HE). Each group consisted of nine individuals. The steers were fed diets with energy levels of 6.657 MJ/kg (LE), 7.323 MJ/kg (ME), and 7.990 MJ/kg (HE) following a 14-day pre-feeding period, with a subsequent 90-day main experimental phase. After the 90-day feeding period, both the HE and ME groups exhibited significantly higher average daily weight gain (ADG) compared to the LE group (p < 0.05). The feed-to-weight ratios were lower in the HE and ME groups compared to the LE group (p < 0.05). The HE group showed significantly higher crude fat content in the longissimus dorsi muscle compared to the LE group (p < 0.05), with total fatty acid content in the muscle surpassing that in the ME and LE groups (p < 0.05). As dietary energy levels increased, the diversity of the rumen microbial community decreased (p < 0.05), and significant differences in bacterial community structure were observed between the LE and HE groups (p < 0.05). The results suggest that higher dietary energy levels enhance growth performance and alter muscle composition in Black Angus steers, while also influencing the rumen microbial community. This study contributes to understanding optimal dietary strategies for finishing Angus cattle to improve beef quality, economic returns, and the development of standardized production procedures. [ABSTRACT FROM AUTHOR]

In this study, we detected signatures of selection in Hanwoo and Angus beef cattle using allele frequency and haplotype-based methods based on imputed whole genome sequence variants. Our dataset included 13,202 Angus animals with 10,057,633 imputed SNPs and 10,437 Hanwoo animals with 13,241,550 imputed SNPs. The dataset was subset down to 6,873,624 SNPs in common between the two populations to identify within population (runs of homozygosity, extended haplotype homozygosity) and between population signals of selection (allele fixation index, extended haplotype homozygosity). Assuming these selection signals were complementary to each other, they were combined into a decorrelated composite of multiple signals to identify regions under selection for each of the breeds. 27 genomic regions spanning 25.15 Mb and harboring 360 genes were identified in Angus on chromosomes 1,3, 4, 5, 6, 7, 8, 12, 13, 14, 16, 20, 21 and 28. Similarly, in Hanwoo, 59 genes and 17 genomic regions spanning 5.21 Mb on chromosomes 2, 4, 5, 6, 7, 8, 9, 10, 13, 17, 20 and 24 were identified. Apart from a small region on chromosome 13, there was no major overlap of selection signals between the two breeds reflecting their largely different selection histories, environmental challenges, breeding objectives and breed characteristics. Positional candidate genes identified in selected genomic regions in Angus have been previously associated with growth, immunity, reproductive development, feed efficiency and adaptation to environment while the candidate genes identified in Hanwoo included important genes regulating meat quality, fat deposition, cholesterol metabolism, lipid synthesis, neuronal development, and olfactory reception.

Background: We investigated breed and gender variations in the compositions of long-chain (≥ C20) omega-3 polyunsaturated fatty acids (LC omega-3 PUFA), fat melting point (FMP) and intramuscular fat (IMF) contents in biopsy samples of the M. longissimus dorsi muscle of grazing beef cattle. The hypothesis that biopsy compositions of health-beneficial LC omega-3 PUFA, FMP and IMF in a pasture-based production system will vary with breed, was tested. Muscle biopsies were taken from 127 yearling pasture-based Angus, Hereford, and Wagyu heifers and young bulls exclusive to the Australian Bowen Genetics Forest Pastoral breeding stud averaging 12 ± 2.43 months of age and under the same management routine. Results: Breed had a significant influence on IMF, FMP, and the compositions of oleic acid, α-linolenic acid (ALA), eicosapentaenoic (EPA), docosahexaenoic (DHA), docosapentaenoic (DPA), and total EPA + DHA + DPA in the M. longissimus dorsi muscle biopsies (P ≤ 0.03). The Wagyu breed had the highest (11.1%) and Hereford the lowest (5.9%) IMF (P = 0.03). The reverse trend was observed in FMP values where the Hereford breed had the highest (55 °C), Angus intermediate (46.5 °C), and Wagyu the lowest (33 °C) FMP. The Wagyu and Angus breeds had similar oleic fatty acid (18:1n-9) content, while the Hereford breed had the lowest (P < 0.01). The highest ALA, DPA, total EPA + DHA, total EPA + DHA + DPA and total ALA + EPA + DHA + DPA contents were detected in the Wagyu breed (P ≤ 0.03). The Hereford had similar EPA and DPA contents to the Angus (P ≥ 0.46). Total EPA + DHA + DPA contents in Wagyu, Angus, and Hereford were 28.8, 21.5, and 22.1 mg/100g tissue (P = 0.01), respectively. Sex was an important source of variation that influenced LC omega-3 PUFA composition, FMP and IMF, where yearling heifers had higher IMF (11.9% vs 5.3%), lower FMP (33°C vs 37°C), and higher LC omega-3 PUFA than bulls. Conclusion: All the results taken together indicate that the Wagyu breed at 28.8 mg/100g tissue, was the closest to meeting the Australia and New Zealand recommended source level threshold of 30 mg/100g tissue of health-beneficial ≥ C20 omega-3 FA content. Since gender was a significant determinant of LC omega-3 PUFA composition, IMF content and FMP, it should be factored into enhancement strategies of healthy meat eating quality traits in grazing cattle. These findings also suggest that the Bowen Genetics Forest Pastoral beef cattle studs are important sources of LC omega-3 PUFA that can be used to cover the deficit in these health claimable fatty acids in Western diets. [ABSTRACT FROM AUTHOR]

Cattle lose heat predominantly through cutaneous evaporation at the skin-hair coat interface when experiencing heat stress. Sweating ability, sweat gland properties, and hair coat properties are a few of the many variables determining the efficacy of evaporative cooling. Sweating is a significant heat dissipation mechanism responsible for 85% of body heat loss when temperatures rise above 86°F. The purpose of this study was to characterize skin morphological parameters in Angus, Brahman, and their crossbred cattle. Skin samples were taken during the summer of 2017 and 2018 from a total of 319 heifers from six breed groups ranging from 100% Angus to 100% Brahman. Epidermis thickness decreased as the percentage of Brahman genetics increased where the 100% Angus group had a significantly thicker epidermis compared to the 100% Brahman animals. A more extended epidermis layer was identified in Brahman animals due to more pronounced undulations in this skin layer. Breed groups with 75% and 100% Brahman genes were similar and had the largest sweat gland area, indicative of superior resilience to heat stress, compared to breed groups with 50% or lower Brahman genetics. There was a significant linear breed group effect on sweat gland area indicating an increase of 862.0 µm2 for every 25% increase in Brahman genetics. Sweat gland length increased as the Brahman percentage increased, while the sweat gland depth showed an opposite trend, decreasing from 100% Angus to 100% Brahman. The number of sebaceous glands was highest in 100% Brahman animals which had about 1.77 more sebaceous glands (p < 0.05) per 4.6 mm2area. Conversely, the sebaceous gland area was greatest in the 100% Angus group. This study identified significant differences in skin properties related to heat exchange ability between Brahman and Angus cattle. Equally important, these differences are also accompanied by significant levels of variation within each breed, which is indicative that selection for these skin traits would improve the heat exchange ability in beef cattle. Further, selecting beef cattle for these skin traits would lead to increased resilience to heat stress without disrupting production traits. [ABSTRACT FROM AUTHOR]

The aim was to evaluate the effect of different rates of weight gain during the backgrounding on animal performance and carcass and meat characteristics of steers finished in feedlots. Thirty‐six Angus steers, 12 ± 2 months of age, were backgrounded during 91 days on Aruana grass pasture (Panicum maximum cv. Aruana) managed under different stocking rates to achieve three different weight gains: HIGH ADG (average daily gain)—no feed restriction (ADG = 0.846 kg); MEDIUM ADG—moderate feed restriction (ADG = 0.456 kg); and LOW ADG—high feed restriction (ADG = 0.154 kg). To ensure the difference in ADG, we offered 0.7% live weight of concentrate feed in the HIGH treatment and a better forage supply in the MEDIUM treatment. After the backgrounding, the animals were finished in feedlot. There was no effect of the previous performance on the animals' performance in the feedlot. The LOW presented higher weight (218.9 vs. 207.9 kg) and hot (54.0% vs. 51.3%) and cold (53.5% vs. 50.5%) carcass yield than the MEDIUM, besides presenting meat with less cooking losses (15.0% vs. 18.2%), marbling (7 vs. 4.0 points), palatability (7.1 vs. 6.3 points), juiciness (7.2 vs. 6.4 points), tenderness (7.1 vs. 6.3 points), and lower shear force (5.78 vs. 8.75 kg) than HIGH. LOW ADG steers stay longer in the finishing phase but presented in general better quality carcass and meat than those with MEDIUM or HIGH during the backgrounding. [ABSTRACT FROM AUTHOR]

Simple Summary: Microorganisms inhabiting the gut influence the health and productivity of livestock. Studies in ruminants including beef cattle show that ruminal microorganisms can help convert poor-quality or indigestible feed into nutrients, thereby influencing economically important traits like feed conversion efficiency and meat quality (e.g., marbling), and also interact with receptors on intestinal epithelial cells to regulate a variety of physiological processes including immune responses. Studies have also shown that the proportions of different groups of microorganisms in the gut are influenced by exposure to stress. In beef cattle, given that most cattle are finished on feedlots, induction into feedlots can expose cattle to stress due to transportation, change in diet and change in the handling and management of animals. Therefore, the primary objective of this study was to characterise how gut microorganisms change over time when cattle are inducted into feedlots. The results indicate that there are significant changes in the profiles of gut microorganisms in cattle that are visible soon after feedlot placement. These changes primarily include a reduced diversity of microorganisms within the gut of individual cattle and increased differences in the types of microorganisms that inhabit the gut of different cattle. The microbial communities that inhabit the intestinal tract play an important role in modulating health and productivity. Environmental stressors can impact microbial communities, which can significantly influence host physiology. Cattle are subjected to several environmental stressors when placed on feedlots, such as transportation stress, exposure to feedlot environments and change in diet and management. Exposure to these stressors could influence host gut microbiota, which in turn, could potentially influence host health and performance. The aim of the current study was to characterise the temporal changes that occur in intestinal microbiota as a consequence of feedlot placement by profiling 16s rRNA sequences in rectal faecal samples. When faecal microbiome profiles were compared in terms of relative abundances and alpha diversity metrics, the results showed significant, observable changes in profiles 2 days post-feedlot induction. Furthermore, beta-diversity analysis indicated that the phylogenetic similarity between samples significantly decreased on day 2 (PERMANOVA, p < 0.001). These trends were suggestive of a short-term reduction in microbial diversity coupled with decreased similarity between animals. These changes warrant further investigation and could provide opportunities for improved performance, health and even welfare of feedlot cattle in future. [ABSTRACT FROM AUTHOR]

In this scientific paper, the productive performances of beef cattle belonging to the Aberdeen Angus and Charolaise breeds from 6 farms in Neamț County were analyzed, studying the following indicators: birth weight (kg), body weight (kg), and average daily gain (g) at the age of 200 days (kg), and also 365 days (kg). The data on average values and variability of meat production indices show that the highest performances were 42.33 kg at birth, 246.29 kg and the average daily increase of 1030.71 grams per 200 days, and 433.69 kg with the average daily increase of 1074.33 kg, at the age of 365 days. On the last place was farm 1, which registered an average weight at birth of 30.70 kg, at 200 days this indicator was 188.59 kg, and the average daily gain was 786.20 grams; at 365 days the average weight was 320.84 kg and the average weight was 793.11 kg. Farm 1 raises the Aberdeen Angus breed, and farm 5 raises the Charolaise breed, which has better results due to the constant care of the breeder to improve the genetic material. [ABSTRACT FROM AUTHOR]

Summary: Explicitly fitting effects for major genes or QTL that account for a large percentage of variation in a whole genomic prediction model may increase prediction accuracy. This study compared approaches to account for a major effect of an F94L variant in the MSTN gene within the genomic prediction using bovine whole‐genomic SNP markers. Among the beef cattle breeds, Limousin have been known to have an F94L variant that is not present in Angus. The reference population in this study consisted of 3060 beef cattle including pure‐bred Limousin (PL), cross‐bred Limousin with Angus (LF) and pure‐bred Angus, genotyped using a BovineSNP50 BeadChip and directly for the MSTN‐F94L variant. We compared prediction accuracies in PL animals using the three datasets from only the PL population, admixed PL and LF (AL) or multibreed analysis using all of the PL, LF and Angus (MB) population according to four‐fold cross‐validation after K‐means clustering. The MSTN‐F94L variant was the most strongly associated with five traits (birth weight, calving ease direct, milk, weaning weight and yield grade) among the 13 measured traits in PL and AL populations. Fitting the MSTN‐F94L variant as a random effect, the genomic prediction accuracies for birth weight increased by 2.7% in PL, by 2.2% in AL and by 3.2% in MB. Prediction accuracies for five traits increased in the MB analysis. Fitting MSTN‐F94L as a fixed effect in PL, AL and MB analyses resulted in increased prediction accuracy in PL for eight traits. Prediction accuracies can be improved by including a causal variant in genomic evaluation compared with simply using whole‐genome SNP markers. Fitting the causal variant as a fixed effect along with markers fitted as random effects resulted in greater prediction accuracies for most traits. Causal variants should be genotyped along with SNP markers. [ABSTRACT FROM AUTHOR]

Selection for production traits with little or no emphasis on health-related traits has the potential to increase susceptibility to disease in food-producing animals. A possible genetic strategy to mitigate such effects is to include both production and health traits in the breeding objective when selecting animals. For this to occur, reliable methodologies are required to assess beneficial health traits, such as the immune capacity of animals. We describe here a methodology to assess the immune competence of beef cattle which is both practical to apply on farm and does not restrict the future sale of tested animals. The methodology also accommodates variation in prior vaccination history of cohorts of animals being tested. In the present study, the immune competence phenotype of 1,100 Angus calves was assessed during yard weaning. Genetic parameters associated with immune competence traits were estimated and associations between immune competence, temperament, and stress-coping ability traits were investigated. Results suggested that immune competence traits, related to an animal's ability to mount both antibody and cell-mediated immune responses, are moderately heritable (h 2 = 0.32 ± 0.09 and 0.27 ± 0.08, respectively) and favorably genetically correlated with the temperament trait, flight time (r = 0.63 ± 0.31 and 0.60 ± 0.29 with antibody and cell-mediated immune responses, respectively). Development of methodologies to assess the immune competence phenotype of beef cattle is a critical first step in the establishment of genetic selection strategies aimed at improving the general disease resistance of beef herds. Strategies aimed at reducing the incidence of disease in beef cattle are expected to significantly improve animal health and welfare, reduce reliance on the use of antibiotics to treat disease, and reduce disease-associated costs incurred by producers. [ABSTRACT FROM AUTHOR]

One hundred ninety-one Angus steers (age = 546 d ± 33.5; BW = 36.4 kg ± 4.2), sired by bulls divergently selected for feed efficiency over a 3-yr period, were used to compare growth, efficiency, body composition, and carcass characteristics. Selected Angus sires were either high (Hi) or low (Lo) for residual average daily gain (RADG) expected progeny differences (EPDs) and either high (Hi) or low (AVG; breed average) for marbling (MARB) EPDs. Steer weight and body composition, via ultrasound, were measured at weaning (205 d) and at 1 yr (365 d) of age. Steers entered the feedlot at 454 d of age and completed a 70-d GROWSAFE BEEF System evaluation to determine DMI, ADG, and residual feed intake (RFI). Steers were then slaughtered as they reached a backfat thickness of 1.3 cm. Carcasses were chilled for 48 h at 2 °C, ribbed, and USDA yield and quality grade data were collected. The right side of the carcass was fabricated and primal and subprimal weights were collected. A 2.5-cm longissimus steak was removed, vacuum-packaged, aged for 14 d, and frozen for slice shear force determination. Additionally, a 1.3-cm longissimus steak was removed from year 3 steers for proximate analysis. The GLM procedure of SAS was used and the main effects of RADG and MARB and their interaction were tested by the error term, SIRE(RADG*MARB). Year was evaluated as a replicate. Weight, ultrasound backfat, and REA were increased (P ≤ 0.05) at weaning in the Hi compared with AVG MARB steers. Feed efficiency, measured by RFI, was improved (P = 0.05) in the Hi RADG steers compared with Lo RADG steers. Slaughter weight and HCW were heavier (P ≤ 0.03) in the Hi RADG steers compared with Lo RADG steers. An interaction (P = 0.05) between RADG and MARB selection was found for marbling score, steers selected for Lo RADG and Hi MARB had greater marbling scores than all other groups. Longissimus proximate composition from year 3 showed that lipid content was greater (P < 0.01) in the Hi MARB and Lo RADG groups compared with the AVG MARB and Hi RADG groups, respectively. These findings suggest that selection using RADG or MARB EPDs has minimal impact on carcass yield. However, positive selection pressure placed on these breeding values can potentially improve efficiency and carcass quality. Lastly, it appears that improvements in feed efficiency can be obtained without negatively affecting beef carcass merit, especially USDA quality grade. [ABSTRACT FROM AUTHOR]

Dystocia and perinatal mortality are major animal health, welfare and economic issues in beef suckler cow production. The objective of this study was to identify risk factors for dystocia and perinatal mortality and to analyze the relationships of both traits to external pelvic parameters in extensively kept beef suckler cows. Calving ease and calf survival were recorded for 785 births on five Angus cattle farms in Germany. The prevalence of dystocia and perinatal mortality was 3.4% and 4.3%, respectively. A hierarchical model was used to predict dystocia and perinatal mortality. First-parity dams had a higher probability of dystocia (p < 0.0001) than later-parity ones. Increasing birth weight was associated with an increasing risk for dystocia (p < 0.05). The probability of perinatal mortality (p < 0.0001) was higher in assisted births than in unassisted births. Calves from first-parity dams had a higher risk (p < 0.01) of being stillborn than calves from dams in later parities. An increase in the length of the pelvis was associated with an increase in odds for perinatal mortality (p < 0.001). In conclusion, the study indicates that dystocia and perinatal mortality are mainly problems in first-parity suckler cows. Concerning the predictive value of external pelvic parameters, further research is necessary.

Os objetivos neste estudo foram avaliar um modelo animal multirracial (MAMR) heterocedástico para estimar a heterogeneidade de variância residual devida à raça, à heterozigosidade, ao sexo e ao grupo de contemporâneos (GC) e a robustez a dados extremos. Foram avaliadas diferenças nas estimativas de componentes de variância, herdabilidades e valores genéticos. Foram utilizados 4.016 registros de ganho de peso pós-desmame (GPD) do rebanho de formação da raça Brangus-Ibagé da Embrapa Pecuária Sul. Os dados foram analisados por um MAMR com quatro especificações diferentes da distribuição dos resíduos, definidas pela natureza da variância residual homocedástica (HO) ou heterocedástica (HE) e pela distribuição marginal dos resíduos Gaussiana (G) ou t de Student (T). O melhor ajuste aos dados foi pelo MAMR-T-HE e foi observada heterocedasticidade devida ao sexo e à heterozigosidade dos animais e entre grupos de contemporâneos. Houve diferenças substanciais nas variâncias genéticas de grupos raciais estimadas utilizando-se diferentes modelos e nos heterocedásticos, MAMR-G-HE e MAMR-T-HE. As maiores diferenças nas estimativas de herdabilidade ocorreram entre grupos raciais diferentes. Também foram observados reordenamentos na classificação de animais superiores quanto ao mérito genético quando variâncias residuais heterogêneas e robustez a dados extremos foram consideradas. Avaliações genéticas multirraciais utilizando o modelo t de Student para descrever resíduos e assumindo variâncias residuais heterogêneas são mais apropriadas para realizar interferência no mérito genético de animais produtos de cruzamento entre as raças Angus e Nelore.The objectives of this study were to evaluate a multibreed heteroskedastic animal model (MAMR) to estimate residual variance heterogeneity due to breed, heterozigosity, sex and contemporary groups (CG) and robustness to outliers. Differences on variance components, heritability and genetic values estimates were evaluated. It was used 4,016 records of post weaning weight gain (PWG) from Brangus foundation herd of Embrapa Pecuária Sul. Data were analyzed by MAMR with four different residual distribution specifications, which were defined by the nature of residual variance, homoskedastic (HO) or Heteroskedastic (HE) and by the Gaussian (G) or Student t marginal residual distribution. The best data fit was achived by using MAMR-T-HE and it was observed heteroscedasticity due to sex and animal heterozigosity and among contemporary groups. There were substantial differences in genetic variances of breed groups estimated by using different models and in the heteroskedastic, MAMR-G-HE and MAMR-T-HE. The greatest differences on heritability estimates occured among different breed groups. It was also noted a reordering in the ranking of superior animals regarded to genetic merit when heterogenous residual variances and robustness to outliers were considered. Multibreed genetic evaluations by using the Student t distribution model to describe residuals and assuming heterogenous residual variances are more appropriate to perform inference on genetic merit of animals from crossbreeding progenies of Angus and Nelore purebred animals.

Foram determinados os componentes de (co)variância para caracteres do período pós-desmama na raça Angus e de covariância com peso ao nascer (PN) e caracteres do período pré-desmama por intermédio de um modelo animal. Utilizaram-se dados de 18.921 animais com registros de peso à desmama e ao sobreano, dos quais 4.452 tinham avaliações completas para escores visuais à desmama e ao sobreano. Registros de PN estavam disponíveis para 11.788 animais. As herdabilidades do ganho de peso pós-desmama (GP205) e dos escores de conformação (CS), precocidade (GS), musculatura (MS) e tamanho (TS) ao sobreano foram de 0,20, 0,19, 0,25, 0,26 e 0,24 respectivamente. As correlações genéticas entre os caracteres estudados foram todas positivas: entre GP205 e escores visuais variaram de 0,50 a 0,71; para os escores ao sobreano entre si, de 0,22 a 0,94; entre GP205 e PN foram de 0,14; entre GP205 e ganho pré-desmama, de 0,23; e para o mesmo escore visual observado à desmama e ao sobreano, de 0,90 a 0,99. Esses resultados indicam que é possível selecionar para GP205, sem aumento importante do PN, e que a seleção para GP205 deverá promover uma mudança genética correlacionada em escores visuais ao sobreano.(Co)variance components were determined for post-weaning traits, and covariances with birth weight (BW) and pre-weaning traits, in Angus cattle using an animal model. Records of weaning and yearling weights of 18,921 animals were used and from these 4,452 had complete evaluations of visual scores at weaning and post-weaning phases. Records of BW were available for 11,788 animals. Heritabilities of post-weaning gain (GP205) and visual scores for conformation (YC), precocity (YP), muscling (YM) and size (YS) were 0.20, 0.19, 0.25, 0.26 and 0.24, respectively. Genetic correlations among all traits considered were positive: between GP205 and visual scores the range was from 0.50 to 0.71; for yearling scores among themselves from 0.22 to 0.94; between GP205 and BW was 0.14; between GP205 and pre-weaning gain was 0.23 and for the same score at weaning and yearling stages they varied from 0.90 to 0.99. These results indicate that it is possible to select for GP205 without a significant increase in BW and that the selection for GP205 should produce a correlated genetic change on yearling visual scores.

Genomically estimated breeding values (GEBV) for Angus beef cattle are available from at least 2 commercial suppliers (Igenity [http://www. igenity.com] and Zoetis [http://www.zoetis.com]). The utility of these GEBV for improving genetic evaluation depends on their accuracies, which can be estimated by the genetic correlation with phenotypic target traits. Genomically estimated breeding values of 1,032 Angus bulls calculated from prediction equations (PE) derived by 2 different procedures in the U.S. Angus population were supplied by Igenity. Both procedures were based on Illuminia BovineSNP50 BeadChip genotypes. In procedure sg, GEBV were calculated from PE that used subsets of only 392 SNP, where these subsets were individually selected for each trait by BayesCπ. In procedure rg GEBV were calculated from PE derived in a ridge regression approach using all available SNP. Because the total set of 1,032 bulls with GEBV contained 732 individuals used in the Igenity training population, GEBV subsets were formed characterized by a decreasing average relationship between individuals in the subsets and individuals in the training population. Accuracies of GEBV were estimated as genetic correlations between GEBV and their phenotypic target traits modeling GEBV as trait observations in a bivariate REML approach, in which phenotypic observations were those recorded in the commercial Australian Angus seed stock sector. Using results from the GEBV subset excluding all training individuals as a reference, estimated accuracies were generally in agreement with those already published, with both types of GEBV (sg and rg) yielding similar results. Accuracies for growth traits ranged from 0.29 to 0.45, for reproductive traits from 0.11 to 0.53, and for carcass traits from 0.3 to 0.75. Accuracies generally decreased with an increasing genetic distance between the training and the validation population. However, for some carcass traits characterized by a low number of phenotypic records (weight, intramuscular fat, and eye muscle area), accuracies were observed to increase but had large SE. Therefore, Igenity GEBV can be useful to Australian Angus breeders, either for blending EBV or as the sole basis for selection decisions if no other information is available. However, for carcass traits, additional phenotypic data are required. [ABSTRACT FROM AUTHOR]

The objective was to determine the effects of a decreased interval of progesterone on the ovulatory follicle prior to fixed-timed artificial insemination (FTAI) in a 7 & 7 Synch estrous synchronization protocol using estrus expression (EE), FTAI pregnancy rates (AIPR) on 37±2d, and overall pregnancy rates (OPR) after a 60d bull exposure 90±2d determined via ultrasound. Using conventional Angus semen, multiparous Angus-cross cows (n=201) from two locations were randomized by age and days post-partum into two treatments. Both treatments used a controlled internal drug releasing device (Eazi-breedTM CIDR; 1.38g progesterone) inserted intravaginally -14d of the protocol simultaneous to administration of prostaglandin F2a (PGF; 500µg cloprostenol sodium; Estrumate®). In the first treatment (7&7), gonadotropin-releasing hormone (GnRH; 86µg gonadorelin; Fertagyl®) was administered on -7d. In the second treatment (8&6), GnRH was administered on -6d. Both treatments were then administered PGF simultaneous to CIDR removal on 0d, 66±2h prior to FTAI and administration of GnRH. EE was determined at the time of artificial insemination using an EstrotectTM patch (Rockway Inc., Spring Valley, WI). EE was signified as a patch with 50% or more of the color rubbed off or missing. Subsequently, a patch with less than 50% of the color rubbed off, was not. AIPR, OPR and EE were analyzed by treatment using the GLIMMIX procedure on SAS 9.4 (SAS Institute Inc., Cary, NC.). There was a significant effect on EE (P=0.01), a tendency on PR (P=0.08), and no effect on OPR (P=0.53) by treatment. EE, AIPR, and OPR for 7&7 were 95±2.1%, 82±3.7% and 96.7±1.7% and for 8&6 were 86±4.0%, 91±3.1% and 98±1.5%, respectively. In conclusion, the altered timeframe of GnRH administration affected EE and tended to affect PR in multiparous beef cows, suggesting that GnRH administration may improve PR when administered 6d, instead of 7d, prior to CIDR removal. [ABSTRACT FROM AUTHOR]

Linkage disequilibrium (LD) and the persistence of its phase across populations are important for genomic selection as well as fine scale mapping of quantitative trait loci. However knowledge of LD in beef cattle, as well as the persistence of LD phase between crossbreds and purebreds, is limited. The objective of this study was to understand the patterns of LD in Angus, Charolais, and crossbred beef cattle based on 31’073, 32’088 and 33’286 SNP in each population, respectively. Amount of LD decreased rapidly from 0.29 to 0.23 to 0.19 in Angus (AN), 0.22 to 0.16 to 0.12 in Charolais (CH), 0.21 to 0.15 to 0.11 in Crossbreds (C), when the distance range between markers changed from 0-30kb to 30-70kb and then to 70-100kb, respectively. Breeds and chromosomes had significant effects (P

Background As consumers continue to request food products that have health advantages, it will be important for the livestock industry to supply a product that meet these demands. One such nutrient is fatty acids, which have been implicated as playing a role in cardiovascular disease. Therefore, the objective of this study was to determine the extent to which molecular markers could account for variation in fatty acid composition of skeletal muscle and identify genomic regions that harbor genetic variation. Results Subsets of markers on the Illumina 54K bovine SNPchip were able to account for up to 57% of the variance observed in fatty acid composition. In addition, these markers could be used to calculate a direct genomic breeding values (DGV) for a given fatty acids with an accuracy (measured as simple correlations between DGV and phenotype) ranging from -0.06 to 0.57. Furthermore, 57 1-Mb regions were identified that were associated with at least one fatty acid with a posterior probability of inclusion greater than 0.90. 1-Mb regions on BTA19, BTA26 and BTA29, which harbored fatty acid synthase, Sterol-CoA desaturase and thyroid hormone responsive candidate genes, respectively, explained a high percentage of genetic variance in more than one fatty acid. It was also observed that the correlation between DGV for different fatty acids at a given 1-Mb window ranged from almost 1 to -1. Conclusions Further investigations are needed to identify the causal variants harbored within the identified 1-Mb windows. For the first time, Angus breeders have a tool whereby they could select for altered fatty acid composition. Furthermore, these reported results could improve our understanding of the biology of fatty acid metabolism and deposition. [ABSTRACT FROM AUTHOR]

Intramuscular fat and collagen content are major factors affecting beef quality, but mechanisms regulating intramuscular adipose and connective tissue deposition are far from clear. Japanese Wagyu cattle are well known for their extremely high marbling. The objective of this study was to evaluate intramuscular fat (IMF) and collagen deposition in the muscle of Wagyu compared with Angus cattle. Animals were managed under the same condition and slaughtered at an averaging 585 ± 12.1 kg of BW. Samples of sternomandibularis muscle were collected from Wagyu (n = 3) and Angus (n = 3) for molecular and histological investigations of adipogenesis and fibrogenesis. With exception ofC/EBPβ (P = 0.2864) the expression of the adipogenic markers C/EBPα (P = 0.008), PPARγ (P = 0.028), and zip finger protein 423 (Zfp423; P = 0.047) in Wagyu were greater than in Angus muscle, which was consistent with greater IMF depositionin Wagyu (P < 0.05). In addition, more adipocytes and e preadipocytes were detected intramuscularly in Wagyu cattle. Similarly, fibrogenesis was also enhanced in e Wagyu, with a greater expression of fibroblast growth tfactor (FGF)-2 (P = 0.028), FGF receptor 1 (P = 0.030),transforming growth factor (TGF)-β (P = 0.028), collagen I (P = 0.012), and collagen III (P = 0.025). Similarly, Wagyu muscle had greater collagen content (P = 0.002) and decreased collagen solubility (P = 0.005). In addition, muscle fiber diameter was larger (P < 0.0001) in Wagyu s than in Angus cattle. These results clearly show that both IMF and collagen contents are enhanced in Wagyu cattle and more adipogenic cells are detected in Wagyu muscle, indicating intramuscular adipogenesis is enhanced in Wagyu compared with Angus muscle. [ABSTRACT FROM AUTHOR]

Abstract: This study evaluated the resistance of cattle of different genetic groups to the tick Rhipicephalus microplus and the relationship with traits of the animals’ hair and coat. Cows of the Senepol×Nelore (SN), Angus×Nelore (AN) and Nelore (NX) genetic groups were submitted to four consecutive artificial infestations, at 14-day intervals, each one with approximately 20,000 tick larvae placed on the animals’ lumbar region. From the 19th to 23rd day of each infestation five counts of the number of ticks were performed on each animal''s left body side. The tick count data (TTC) were transformed into log10 (n +1), and also into percentage of return (PR), where n is the total number of ticks counted at each infestation. Hair samples were collected 24h after the last infestation with flat-nosed pliers. Measures of the average hair length (HL), coat thickness (CT), number of hairs per cm2 (NHCM2) and weight of the samples (SW) were obtained. Pearson''s correlation coefficients were calculated within genetic group to measure association between PR and the hair and coat data. There was a significant difference among genetic groups for the number of ticks, with the AN group having higher counts than the SN and NX groups. For the hair and coat traits, the NX and SN groups had lower values of HL and SW than did the AN group. The SN genetic group had lower NHCM2 counts than the NX and AN groups. There were positive correlations between TTC and CT (P <0.05) and SW (P <0.05) in the SN group. No significant correlation was found for the AN genetic group (P >0.05). [Copyright &y& Elsevier]

The objective of this study was to compare performance and aspects of adaptability attributes of cattle from a Florida Angus bloodline (local source from a mostly closed herd for over 50 yr) to cattle that are representative of modern Angus bloodlines (outside source) in US subtropical conditions. Embryos from both sources were transferred to Brahman-crossbred cows in South Florida, and calves (n = 82) were born in 3 yr. Before weaning, summer tympanic temperatures were recorded hourly for 3 d in each year. Heifers were placed with fertile bulls until diagnosed pregnant. Traits relative to sexual maturation of bulls were recorded at 1- or 2-mo intervals until approximately 17 mo of age. Calves from outside sources had greater hip height at weaning than calves from the local source (P < 0.001; 108.8 ± 0.62 and 104.7 ± 0.68 cm, respectively). Local-source calves (n = 37) had greater (P = 0.03) exit velocity (2.7 ± 0.3 m/s) than outside-source (n = 45) calves (2.0 ± 0.29 m/s), which may be indicative of more nervous or temperamental disposition. However, no source differences were detected for other assessments of disposition (chute or pen score, P > 0.8). Few source differences for minimum, maximum, or range of daily tympanic (inner ear) temperatures were detected. At 17 mo of age, outside-source heifers were heavier (P = 0.05) and had greater (P < 0.001) hip height than Angus heifers from the local source. Heifers from the outside source were younger (P < 0.001) at the time of their first conception (454 ± 17.5 d) than heifers from the local source (550 ± 16.9 d). Outside-source heifers also had greater (P < 0.02) pregnancy and calving rates (0.7 ± 0.119 and 0.62 ± 0.125, respectively) from exposure to bulls within a year from weaning than the heifers from the local source (0.29 ± 0.089 and 0.19 ± 0.077, respectively). Bulls from the outside source were heavier (P = 0.05) at 320 d of age than local-source bulls. From 14 through 17 mo of age, outside-source bulls had greater (P ⩽ 0.05) scrotal circumference and tended (P ⩽ 0.15) to be heavier than local-source bulls. There appeared to be no performance or adaptation advantages for the local-source Angus through 17 mo of age. The large source difference for age at first conception in heifers merits additional attention and comparison with cow lifetime production performance for the 2 sources. [ABSTRACT FROM AUTHOR]

Wagyu-sired (n = 20) and Angus-sired (n = 19) steers and heifers were used to compare the effects of sire breed on feedlot performance, carcass characteristics, and meat tenderness. Calves were weaned at 138 ± 5 d of age and individually fed a finishing diet consisting of 65% whole corn, 20% protein/vitamin/mineral supplement, and 15% corn silage on a DM basis. Heifers and steers were slaughtered at 535 and 560 kg of BW, respectively. Carcasses were ribbed between the 12th and 13th (USDA grading system) and the 6th and 7th ribs (Japanese grading system) to measure fat thickness, LM area (LMA), and intramuscular fat (IMF). Two steaks were removed from the 12th rib location and aged for 72 h and 14 d to determine Warner-Bratzler shear force and cooking loss. Sire breed x sex interactions were not significant (P> 0.05). Angussired calves had greater (P < 0.05) ADG and DMI than Wagyu. Wagyu-sired calves had improved (P < 0.05) feed efficiency than Angus. Sire breed did not affect (P> 0.20) HCW, 12th-rib fat, or USDA yield grade. Carcasses of Wagyu had greater (P = 0.0001) marbling scores at the 12th rib than those of Angus (770.9 vs. 591.3 ± 41.01, respectively). Carcasses of Wagyu also had greater (P < 0.02) 12th-rib IMF and 6th-rib IMF than Angus, resulting in a greater proportion of carcasses grading Prime (65.0 vs. 21.1%; P = 0.006). Carcasses from Wagyu tended (P = 0.08) to have greater LMA at the 12th rib, whereas Angus carcasses had greater (P < 0.05) LMA at the 6th rib. Steaks from Angus and Wagyu had similar (P> 0.50) tenderness at aging times of 72 h and 14 d. Cooking loss was greater (P < 0.01) for Angus than Wagyu steaks at 72 h and 14 d. Using Wagyu sires vs. Angus sires on British-based commercial cows combined with early weaning management strategies has the potential to produce a product with greater marbling, but is unlikely to significantly enhance tenderness. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this study were to develop an accurate and precise method for cholesterol quantification in meat samples based on modifications made to an existing procedure (AOAC Official Method 994.10), and to apply this modified method to evaluate cholesterol levels in longissimus muscles (LM) from Angus (AN, n=5), Brahman (BR, n=4), and Romosinuano (RM, n=9) breeds. Validation of this method was performed using a meat homogenate (Standard Reference Material 1546) from National Institute of Standards and Technology (NIST), and LM samples from the three breeds with fat contents ranging from 2.4% to 9.3%. The results indicated that the modified method was accurate with cholesterol recovery exceeding 95%. The method was also found to be precise with an average coefficient of variation of 3.12%. The modification reduced 90% of chemicals used and eliminated time-consuming steps that hindered high throughput application of the traditional method. The application of this method to quantify cholesterol contents of LM samples revealed differences among the three breeds evaluated. The Angus LM with a higher fat content (50% higher) was associated with a significantly higher cholesterol concentration (70.25mg/100g) as compared to LM from Brahman and Romosinuano purebreds (64.77 and 65.76mg/100g; P=0.005 and 0.006, respectively). Cholesterol concentration was found to be correlated with the i.m. fat content of LM muscle from the three breeds (r=0.90, P<0.001). Cholesterol concentrations of LM determined in this study were comparable to those reported in the USDA National Nutrient Database for Standard Reference for separable lean from Choice rib-eye steaks. This modified method was reliable and should be evaluated for adoption as an appropriate method for cholesterol quantification in meat samples. [Copyright &y& Elsevier]

Presents abstracts of several studies on animal breeding and genetics. "The Impact of Herd Opportunity and Milk Recording Periods in Estimating Lifetime Net Income," by E. Yook, R. E. Pearson and B. G. Cassell; "Joint Genetic Evaluation of Male and Female Fertility Using Longitudinal Binary Responses," by R. Rekaya and T. Averil; "Contribution of Inbreeding and Recessive Defects to Early Embryo Loss," by P. M. VanRaden and R. H. Miller; "Effects of Climate and Photoperiod on Feed Intake of Beef Bulls During Feedlot Performance Tests," by G. T. Tabler Jr., A. H. Brown Jr., Z. B. Johnson, E. E. Gbur Jr., I. L. Berry, D. W. Kellogg and K. C. Thompson.

Presents abstracts of several studies on animal breeding and genetics. "The Impact of Herd Opportunity and Milk Recording Periods in Estimating Lifetime Net Income," by E. Yook, R. E. Pearson and B. G. Cassell; "Joint Genetic Evaluation of Male and Female Fertility Using Longitudinal Binary Responses," by R. Rekaya and T. Averil; "Contribution of Inbreeding and Recessive Defects to Early Embryo Loss," by P. M. VanRaden and R. H. Miller; "Effects of Climate and Photoperiod on Feed Intake of Beef Bulls During Feedlot Performance Tests," by G. T. Tabler Jr., A. H. Brown Jr., Z. B. Johnson, E. E. Gbur Jr., I. L. Berry, D. W. Kellogg and K. C. Thompson.

Presents abstracts of several studies on animal breeding and genetics. "The Impact of Herd Opportunity and Milk Recording Periods in Estimating Lifetime Net Income," by E. Yook, R. E. Pearson and B. G. Cassell; "Joint Genetic Evaluation of Male and Female Fertility Using Longitudinal Binary Responses," by R. Rekaya and T. Averil; "Contribution of Inbreeding and Recessive Defects to Early Embryo Loss," by P. M. VanRaden and R. H. Miller; "Effects of Climate and Photoperiod on Feed Intake of Beef Bulls During Feedlot Performance Tests," by G. T. Tabler Jr., A. H. Brown Jr., Z. B. Johnson, E. E. Gbur Jr., I. L. Berry, D. W. Kellogg and K. C. Thompson.

The article focuses on study on effects of U.S. and New Zealand Angus germplasm on characteristics of crossbred calves. Topics discussed include preweaning and postweaning growth rates were similar for calves of the U.S. and New Zealand paternity, animals have undergone natural selection for reproduction and survival and artificial selection and differences attributable to sire paternity in blood concentration at birth.

The article presents the study which examined the milk production in Brahman and Angus cows on endophyte-infected fescue and common bermuda grass. It offers details of the method of the study which involved estimation of the milk production using single-cow portable machine at a number of days of postpartum.

• Electrical stimulation of nellore-angus carcasses influenced 5 of 30 steak flavors. • SNP on BTA 4, 5, and 12 were associated with cooked beef lean flavor. • Two SNP (BTA 16 and 23) were associated with acid flavor post electrical stimulation. • One SNP on BTA 11 was associated with metallic flavor post electrical stimulation. • Beef flavor traits had low or no relationships with steer temperament traits. Steaks from Bos indicus -influenced steers (n = 350) were evaluated for beef flavor and aromatic traits. Electrical stimulation status was a fixed effect. Genome-wide association was conducted with 34,957 SNP from a commercial array using a mixed linear model. Significant effects of electrical stimulation were less intense acid and browned flavors, and more intense cooked beef lean and livery flavors (P < 0.05). There were no strong simple or residual correlations among the flavor traits with carcass quantity, quality, sensory panel palatability, or temperament traits of steers. There were 18 (no electrical stimulation; chemical burn, cooked beef lean, livery, sour) and 8 (electrical stimulation; acid, chemical burn, cooked beef lean, metallic) SNP associated with flavor traits (FDR < 0.18). Closest genes to these were involved in neural/neuronal processes or cellular and extracellular structure. [ABSTRACT FROM AUTHOR]

• Nine SNP on BTA 29 were associated with tenderness traits. • One SNP on BTA 4 was associated with juiciness score. • Associations on BTA 29 may be affiliated with CAPN1 , but this was not confirmed. • Electrical stimulation may suppress SNP-connective tissue amount associations. • Palatability traits had low or no relationships with measured temperament traits. Genome wide association analyses were conducted for palatability traits in the presence or absence of electrical stimulation. Palatability traits were measured on steaks from Nellore-Angus steers (n = 350). No palatability traits were correlated (| r | < 0.18) with steer temperament. Nine SNP on BTA 29 from 35.7 Mb to 48.2 Mb were associated with muscle fiber or overall tenderness, and/or connective tissue amount measured on steaks from carcass sides not electrically stimulated. Only three of these SNP were associated with these traits on the electrically stimulated carcass side. Associated SNP with connective tissue amount were only detected in steaks from carcass sides not subjected to electrical stimulation. Sixteen other BTA 29 SNP were associated with at least one tenderness trait from the electrically stimulated carcass side. One SNP on BTA 4 and 24 were associated with juiciness and overall tenderness, respectively. Candidate genes on BTA 29 included EGF containing fibulin extracellular matrix protein 2 (EFEMP), slingshot protein phosphatase 3 (SSH3), achaete-scute family bHLH transcription factor 2 (ASCL2). Although not detected as a candidate gene, the associated SNP with the various tenderness traits on BTA 29 may indicate the importance of calpain 1 (CAPN1), which has been considered influential on beef tenderness. [ABSTRACT FROM AUTHOR]

Presents abstracts of studies on molecular genetics, QTL detection and marker assisted selection in cattle. "Detection of Quantitative Trait Loci Affecting Conformation Traits in Holstein Cattle," by M.S. Ashwell, D.W. Heyen, T.S. Sonstegard, C.P. Van Tassell and H.A. Lewin; "Statistical Power For Detecting Epitasis QTL Effects Under the F2 Design," Y. Mo and Y. Da; "Evaluation of Microsatellite Markers on Bovine Chromosomes 1 and 5 for Potential Allelic Associations With Meat Characteristics and Growth Traits in Beef Cattle," by K.S. Kim, S. Costello. G.J.M. Rosa, A.M. Mullen, N.E. Raney, C.W. Ernst.

Presents abstracts of studies on molecular genetics, QTL detection and marker assisted selection in cattle. "Detection of Quantitative Trait Loci Affecting Conformation Traits in Holstein Cattle," by M.S. Ashwell, D.W. Heyen, T.S. Sonstegard, C.P. Van Tassell and H.A. Lewin; "Statistical Power For Detecting Epitasis QTL Effects Under the F2 Design," Y. Mo and Y. Da; "Evaluation of Microsatellite Markers on Bovine Chromosomes 1 and 5 for Potential Allelic Associations With Meat Characteristics and Growth Traits in Beef Cattle," by K.S. Kim, S. Costello. G.J.M. Rosa, A.M. Mullen, N.E. Raney, C.W. Ernst.

Presents abstracts of studies on molecular genetics, QTL detection and marker assisted selection in cattle. "Detection of Quantitative Trait Loci Affecting Conformation Traits in Holstein Cattle," by M.S. Ashwell, D.W. Heyen, T.S. Sonstegard, C.P. Van Tassell and H.A. Lewin; "Statistical Power For Detecting Epitasis QTL Effects Under the F2 Design," Y. Mo and Y. Da; "Evaluation of Microsatellite Markers on Bovine Chromosomes 1 and 5 for Potential Allelic Associations With Meat Characteristics and Growth Traits in Beef Cattle," by K.S. Kim, S. Costello. G.J.M. Rosa, A.M. Mullen, N.E. Raney, C.W. Ernst.

Background: Genome-wide association studies (GWAS) are extensively used to identify single nucleotide polymorphisms (SNP) underlying the genetic variation of complex traits. However, much uncertainly often still exists about the causal variants and genes at quantitative trait loci (QTL). The aim of this study was to identify QTL associated with residual feed intake (RFI) and genes in these regions whose expression is also associated with this trait. Angus cattle (2190 steers) with RFI records were genotyped and imputed to high density arrays (770 K) and used for a GWAS approach to identify QTL associated with RFI. RNA sequences from 126 Angus divergently selected for RFI were analyzed to identify the genes whose expression was significantly associated this trait with special attention to those genes residing in the QTL regions. Results: The heritability for RFI estimated for this Angus population was 0.3. In a GWAS, we identified 78 SNPs associated with RFI on six QTL (on BTA1, BTA6, BTA14, BTA17, BTA20 and BTA26). The most significant SNP was found on chromosome BTA20 (rs42662073) and explained 4% of the genetic variance. The minor allele frequencies of significant SNPs ranged from 0.05 to 0.49. All regions, except on BTA17, showed a significant dominance effect. In 1 Mb windows surrounding the six significant QTL, we found 149 genes from which OAS2, STC2, SHOX, XKR4, and SGMS1 were the closest to the most significant QTL on BTA17, BTA20, BTA1, BTA14, and BTA26, respectively. In a 2 Mb windows around the six significant QTL, we identified 15 genes whose expression was significantly associated with RFI: BTA20) NEURL1B and CPEB4; BTA17) RITA1, CCDC42B, OAS2, RPL6, and ERP29; BTA26) A1CF, SGMS1, PAPSS2, and PTEN; BTA1) MFSD1 and RARRES1; BTA14) ATP6V1H and MRPL15. Conclusions: Our results showed six QTL regions associated with RFI in a beef Angus population where five of these QTL contained genes that have expression associated with this trait. Therefore, here we show that integrating information from gene expression and GWAS studies can help to better understand the genetic mechanisms that determine variation in complex traits. [ABSTRACT FROM AUTHOR]

Dystocia and perinatal mortality are major animal health, welfare and economic issues in beef suckler cow production. The objective of this study was to identify risk factors for dystocia and perinatal mortality and to analyze the relationships of both traits to external pelvic parameters in extensively kept beef suckler cows. Calving ease and calf survival were recorded for 785 births on five Angus cattle farms in Germany. The prevalence of dystocia and perinatal mortality was 3.4% and 4.3%, respectively. A hierarchical model was used to predict dystocia and perinatal mortality. First-parity dams had a higher probability of dystocia (p < 0.0001) than later-parity ones. Increasing birth weight was associated with an increasing risk for dystocia (p < 0.05). The probability of perinatal mortality (p < 0.0001) was higher in assisted births than in unassisted births. Calves from first-parity dams had a higher risk (p < 0.01) of being stillborn than calves from dams in later parities. An increase in the length of the pelvis was associated with an increase in odds for perinatal mortality (p < 0.001). In conclusion, the study indicates that dystocia and perinatal mortality are mainly problems in first-parity suckler cows. Concerning the predictive value of external pelvic parameters, further research is necessary. [ABSTRACT FROM AUTHOR]