Prediction of the chemical body composition of Nellore and crossbreed bulls.

Young Nellore and crossbreed bulls were comparatively slaughtered to generate equation models for predicting the chemical composition of the empty body and carcass from the chemical composition of the Hankins and Howe section (; ). Data were collected from 236 animals from different genetic groups: Nellore, one-half Canchim + one-half Nellore, one-half Angus + one-half Nellore, and one-half Simmental + one-half Nellore, with 48 baseline animals (BW range from 218 to 433 kg) and 188 animals finished in the feedlot (BW range from 356 to 618 kg). The chemical composition prediction equation model was developed for all genetic groups using stepwise regression analysis. Across all animals, the percentages of water and ether extract in the HH section were highly correlated ( < 0.001) with the percentages in the carcass ( = 0.911 and = 0.901, respectively, for water content of the carcass [HOC] and = 0.921 and = 0.921, respectively, for ether extract content of the carcass [EEC]) and empty body ( = 0.937 and = 0.926, respectively, for water content of the empty body [HOEB] and = 0.935 and = 0.939, respectively, for ether extract content of the empty body [EEEB]). The best prediction models were for the traits of empty body weight, HOEB, EEEB, HOC, and EEC. Determination coefficients for predicting the dependent variables obtained from the carcass composition were lower than those obtained from the empty body composition. It was concluded that the chemical composition of the empty body and the carcass can be predicted from the composition of the HH section, using a general equation for different genetic groups.

Effect of the genetic group, production system and sex on the meat quality and sensory traits of beef from crossbred animals.

The crossbreeding of two or more breeds from the Bos taurus and Bos indicus species is an alternative for obtaining high-quality meat from animals adapted to tropical climates. Quality and sensory attributes of beef, mainly its tenderness and flavour, are very important with regard to the consumer's point of view. This study aimed to evaluate the physico-chemical and sensory characteristics of crossbred young bulls and heifers, the offspring of Angus or Limousin bulls and 1/2 Angus + 1/2 Nellore or 1/2 Simental + 1/2 Nellore cows that were finished on feedlot or pasture. Meat quality traits (pH, colour, cooking loss, water holding capacity and shear force) and sensory parameters (characteristic beef aroma/flavour intensity, strange aroma/flavour intensity, tenderness and juiciness descriptive attributes, flavour, texture (tenderness) and overall acceptance) were evaluated. The genetic group had an effect on the beef pH, but it was not as relevant as the effect of the combination between the production system and the sex or genetic group, which affected many of the quality and sensory traits.

Precocidade sexual, eficiência reprodutiva e desempenho produtivo de matrizes jovens Nelore e cruzadas / Sexual precocity, reproductive efficiency and productive performance of Nelore and crossbred young cows

Com o objetivo de avaliar matrizes da raça Nelore (NE) e cruzadas 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN) e 1/2 Senepol + 1/2 Caracu (SC) quanto à precocidade sexual em sistemas de recria a pasto, eficiência reprodutiva e desempenho produtivo das matrizes em cada grupo genético (GG), matrizes desses grupos foram produzidas por três safras. Foram avaliadas 40 matrizes AN, 37 CN, 51 NE e 43 SC. Para prenhez precoce, matrizes AN apresentaram taxa de prenhez de 92,2% contra 29,1% para CN, 22,6% para SC e 1,1% para NE. Na prenhez convencional, matrizes AN obtiveram 99,4%, 98,8% para CN, 84,4% para SC e 80,0% para NE. A reconcepção das matrizes AN foi 86,3%, 75,1% de CN, 49,6% de NE e 43,6% de SC. Matrizes AN tiveram menor média de idade ao primeiro parto em meses, 26,36±0,79, contra 31,33±0,86 para CN, 33,51±0,98 para SC e 38,08±0,74 para NE. Para peso ao desmame, crias three-cross das AN pesaram mais que as F1 das NE, por volta de 19%. Para relação de peso ao desmame, não houve diferenças estatísticas entre GG. Matrizes AN foram superiores às demais nos aspectos reprodutivos e produtivos, seguidas das matrizes CN.(AU)

With the aim of evaluating Nelore (NE), 1/2 Angus + 1/2 Nelore (AN), 1/2 Caracu + 1/2 Nelore (CN), and 1/2 Senepol + 1/2 Caracu (SC) females for sexual precocity on pasture backgrounding, reproductive efficiency and productive performance of cows and their calves of each genetic group (GG), animals of these groups were produced for three years. A total of 40 AN, 37 CN, 51 NE and 43 SC cows were evaluated. For early heifer pregnancy, AN cows had pregnancy rate of 92.2% compared to 29.1% for CN, 22.6% for SC and 1.1% for NE. For conventional heifer pregnancy AN obtained 99.4%, CN with 98.8%, SC with 84.4% and NE with 80.0%. The first reconception of AN cows were 86.3%, 75.1% for CN, 49.6% for NE and 43.6% for SC. AN cows also had lower age at first calving in months, 26.36±0.79, compared to 31.33±0.86 for CN, 33.51±0.98 for SC and 38.08±0.74 for NE. For weaning weigth the three-cross from AN were heavier than the F1s from NE, by a margin of 19%. For calf:cow weight ratio there was no statistical difference among GG. AN cows were superior to the others in both productive and reproductive aspects, followed by the CN cows.(AU)

Genetic correlations between visual slaughter conformation scores and growth and reproductive traits in Canchim cattle.

We obtained heritability and (co)variance component estimates for slaughter conformation scores at 420 days of age (SCS420), age at calving (first, AFC; second, ASC), calving occurrence until 38 months of age (CP38), weight at 420 days of age (W420), and scrotal circumference at 420 days (SC420) in Canchim (5/8 Charolais + 3/8 Zebu) cattle. A total of 23,168 records of Canchim animals, including 12,493 females and 10,675 males, were analyzed. SCS420 indicated carcass structure, muscle development, and subcutaneous fat deposition. The slaughter conformation score of each animal was relative to the whole contemporary group; 1 corresponded to the lowest expression of the trait and 6 to the highest. Heritabilities, and genetic and residual correlation estimates between SCS420 and reproductive and weight traits, were estimated by multitrait analyses using an animal model with Bayesian inference, employing a linear model for AFC, ASC, SC420, and W420 and a threshold model for CP38 and SCS420. Heritability estimates for SCS420, AFC, ASC, CP38, W420, and SC420 were 0.11, 0.15, 0.15, 0.15, 0.30, and 0.30, respectively. Genetic correlation estimates between SCS420 and the other traits were 0.08 (AFC), 0.58 (ASC), 0.08 (CP38), 0.43 (W420), and 0.17 (SC420). Visual slaughter conformation scores respond to individual selection and can be used as selection criteria in Canchim cattle. Selection to improve sexual precocity would not be effective in improving carcass conformation and composition, and selection for animals with high breeding values for yearling weight may improve slaughter conformation at the yearling stage.

Feed efficiency indexes and their relationships with carcass, non-carcass and meat quality traits in Nellore steers.

Five hundred and seventy-five Nellore steers were evaluated for residual feed intake and residual feed intake and gain and their relationships between carcass, non-carcass and meat quality traits. RFI was measured by the difference between observed and predicted dry matter intake and RIG was obtained by the sum of -1*RFI and residual gain. Efficient and inefficient animals were classified adopting ±0.5 standard deviations from RFI and RIG mean. A mixed model was used including RFI or RIG and contemporary group as fixed effects, initial age as covariate and sire and experimental period as random effects, testing the significance of the regression slope for each evaluated trait. RIG was positively related to longissimus muscle area. Efficient-RFI animals had lower liver and internal fat proportions compared to inefficient-RFI animals. Efficient-RFI and efficient-RIG animals had 11.8% and 11.2% lower extracted intramuscular fat, compared to inefficient-RFI and inefficient-RIG animals, respectively. Efficient-RFI animals had tougher meat compared to inefficient-RFI animals.

Candidate genes for carcass traits in a tropical-adapted Brazilian composite beef breed.

Backfat thickness (BFT) and ribeye area (REA) are important production traits but, because they are measured late in the animal's life, they have not been efficiently included in breeding programs. The aim of this study was to evaluate whether single nucleotide polymorphisms (SNPs) mapped to the leptin, PPARGC1A, PSMC1, CRH, and FABP4 genes, which influence BFT and REA in Canchim cattle, a composite beef breed (5/8 Charolais + 3/8 Zebu). BFT and REA phenotypic records were obtained by ultrasound measurements from 18-month-old animals. All SNP markers were genotyped by restriction fragment length polymorphism-polymerase chain reaction. Restricted maximum likelihood analysis revealed that the non-synonymous SNP located in exon 2 of the FABP4 gene has an additive effect on BFT (P ≤ 0.05). Significant allele substitution effects showed that the substitution of G by A may lead to a decrease of 0.1055 mm in mean BFT. This information can be used for inclusion of this trait-associated marker in commercial SNP panels.

Relationship of efficiency indices with performance, heart rate, oxygen consumption, blood parameters, and estimated heat production in Nellore steers.

The objective of this study was to examine the relationship of efficiency indices with performance, heart rate, oxygen consumption, blood parameters, and estimated heat production (EHP) in Nellore steers. Eighteen steers were individually lot-fed diets of 2.7 Mcal ME/kg DM for 84 d. Estimated heat production was determined using oxygen pulse (OP) methodology, in which heart rate (HR) was monitored for 4 consecutive days. Oxygen pulse was obtained by simultaneously measuring HR and oxygen consumption during a 10- to 15-min period. Efficiency traits studied were feed efficiency (G:F) and residual feed intake (RFI) obtained by regression of DMI in relation to ADG and midtest metabolic BW (RFI). Alternatively, RFI was also obtained based on equations reported by the NRC's to estimate individual requirement and DMI (RFI calculated by the NRC [1996] equation [RFI]). The slope of the regression equation and its significance was used to evaluate the effect of efficiency indices (RFI, RFI, or G:F) on the traits studied. A mixed model was used considering RFI, RFI, or G:F and pen type as fixed effects and initial age as a covariate. For HR and EHP variables, day was included as a random effect. There was no relationship between efficiency indices and back fat depth measured by ultrasound or daily HR and EHP ( > 0.05). Because G:F is obtained in relation to BW, the slope of G:F was positive and significant ( < 0.05). Regardless of the method used, efficient steers had lower DMI ( < 0.05). The initial LM area was indirectly related to RFI and RFI ( < 0.05); however, the final muscle area was related to only RFI. Oxygen consumption per beat was not related to G:F; however, it was lower for RFI- and RFI-efficient steers, and consequently, oxygen volume (mL·min·kg) and OP (µL O·beat·kg) were also lower ( < 0.05). Blood parameters were not related to RFI and RFI ( > 0.05); however, G:F-efficient steers showed lower hematocrit and hemoglobin concentrations ( < 0.05). Differences in EHP between efficient and inefficient animals were not directly detected. Nevertheless, differences in oxygen consumption and OP were detected, indicating that the OP methodology may be useful to predict growth efficiency.

Repeatability and genotypic correlations of reproductive and productive traits of crossbred beef cattle dams.

Beef cattle production requires reproductive efficiency. However, measures of reproductive traits are not usually collected; consequently, correlated traits that could be used as indicators would be useful. We examined associations between measures of reproductive and productive efficiency that could be used as selection indicators. Data from 194 dams of the genetic groups Angus x Nelore, Caracu x Nelore, and Valdostana x Nelore collected over 4 years were used. The reproductive traits analyzed were days to heat (DH), calving interval (CI), days to calving (DC), and pregnancy rate (PR). The productive traits were dam weight (DW), body condition score (BCS), calf weight (CW), and weaning rate (WR). The effects on the model were: year, genetic group, reproductive status (RS), age, reproductive rest, and breed of bull (CW and WR). Multivariate analyses were performed, using the Bayesian approach via Gibbs sampling. We conclude that the reproductive measures are ineffective as selection indicators, whereas using dam weight may be a good alternative.

A genome-wide scan for selection signatures in Nellore cattle.

Brazilian Nellore cattle (Bos indicus) have been selected for growth traits for over more than four decades. In recent years, reproductive and meat quality traits have become more important because of increasing consumption, exports and consumer demand. The identification of genome regions altered by artificial selection can potentially permit a better understanding of the biology of specific phenotypes that are useful for the development of tools designed to increase selection efficiency. Therefore, the aims of this study were to detect evidence of recent selection signatures in Nellore cattle using extended haplotype homozygosity methodology and BovineHD marker genotypes (>777,000 single nucleotide polymorphisms) as well as to identify corresponding genes underlying these signals. Thirty-one significant regions (P < 0.0001) of possible recent selection signatures were detected, and 19 of these overlapped quantitative trait loci related to reproductive traits, growth, feed efficiency, meat quality, fatty acid profiles and immunity. In addition, 545 genes were identified in regions harboring selection signatures. Within this group, 58 genes were associated with growth, muscle and adipose tissue metabolism, reproductive traits or the immune system. Using relative extended haplotype homozygosity to analyze high-density single nucleotide polymorphism marker data allowed for the identification of regions potentially under artificial selection pressure in the Nellore genome, which might be used to better understand autozygosity and the effects of selection on the Nellore genome.

Análise genética de características de fertilidade, de crescimento e de produtividade em vacas da raça Canchim / Genetic analysis of fertility, growth and productivity traits of Canchim cows

O objetivo deste trabalho foi estimar herdabilidades e correlações genéticas para idade (IPP), peso (PPP) e escore da condição corporal (EPP) ao primeiro parto, tempo de permanência no rebanho (TPR), número (ND10) e quilograma (QD10) de bezerros desmamados em até dez anos de idade, número (NDT) e quilograma (QDT) de bezerros desmamados durante a permanência no rebanho, quilograma de bezerros desmamados por ano de permanência no rebanho (QTPR), peso adulto (PAD) e parâmetros A e k da curva de crescimento de Bertalanffy de fêmeas de um rebanho da raça Canchim. As distribuições a posteriori dos componentes de (co)variância foram obtidas por inferência bayesiana, em análises bicaráter de IPP, PPP e EPP com as outras características. Os modelos estatísticos incluíram os efeitos aleatórios genético aditivo direto e residual e os efeitos fixos de ano e mês de nascimento ou do parto e idade da vaca ao parto, dependendo da característica. As médias a posteriori das herdabilidades foram 0,12 (IPP); 0,51 (PPP); 0,36 (EPP); 0,22 (TPR); 0,24 (ND10); 0,24 (QD10); 0,25 (NDT); 0,23 (QDT); 0,31 (QTPR); 0,56 (PAD); 0,60 (A) e 0,54 (k), indicando que as características possuem variação genética aditiva suficiente para apresentar boa resposta à seleção massal, com exceção de IPP. As correlações genéticas de TPR (-0,35; -0,23 e -0,02), ND10 (-0,33; -0,40 e -0,02), QD10 (-0,47; -0,29 e 0,00), NDT (-0,43; -0,41 e -0,02), QDT (-0,46; -0,28 e 0,00), QTPR (-0,52; -0,35 e 0,00), PAD (0,19; 0,86 e 0,40), A (0,07; 0,09 e -0,18) e k (-0,21; 0,08 e 0,04) com IPP, PPP e EPP, respectivamente, sugerem que a seleção para reduzir a IPP deve melhorar a longevidade e as características de produtividade das fêmeas; porém, o aumento do PPP poderá prejudicá-las...

The objective of this work was to estimate heritabilities and genetic correlations for age at first calving (AFC), weight at first calving (WFC), body condition score at first calving (SFC), culling age (DIH, days in herd), number (NW10) and kilograms (KW10) of calves weaned up to ten years of age, total number (TNW) and total kilograms (TQW) of calves weaned during herd life, kilograms of calves weaned per year in herd (KYH), adult body weight (ABW) and parameters A and k of the Bertalanffy growth curve of females of a Canchim (5/8 Charolais + 3/8 Zebu) beef cattle herd. The variance and covariance components were obtained by two-trait analyses of AFC, WFC and SFC with the other production traits, using the bayesian inference with statistical models that included the additive direct and residual random effects, and the fixed effects of year and month of birth or of calving and calving age, depending on the trait. The posteriori means of the heritability estimates were 0.12 (AFC), 0.51 (WFC), 0.36 (SFC), 0.22 (DIH), 0.24 (NW10), 0.24 (KW10), 0.25 (TNW), 0.23 (TKW), 0.31 (KYH), 0.56 (ABW), 0.60 (A) and 0.54 (k), indicating that these traits have enough additive genetic variation to show response to mass selection. The genetic correlations for DIH (-0.35, -0.23 and -0.02), NW10 (-0.33, -0.40 and -0.02), KW10 (-0.47, -0.29 and 0.00), TNW (-0.43, -0.41 and -0.02), TKW (-0.46, -0.28 and 0.00), KYH (-0.52, -0.35 and 0.00), ABW (0.19, 0.86 and 0.40), A (0.07, 0.09 and -0.18) and k (-0.21, 0.08 and 0.04) with AFC, WFC and SFC, suggest that selection to reduce age at first calving should improve longevity and productivity traits of females, but the increase in body weight at first calving should reduce these traits...

Genome scan for meat quality traits in Nelore beef cattle.

Meat quality traits are economically important because they affect consumers' acceptance, which, in turn, influences the demand for beef. However, selection to improve meat quality is limited by the small numbers of animals on which meat tenderness can be evaluated due to the cost of performing shear force analysis and the resultant damage to the carcass. Genome wide-association studies for Warner-Bratzler shear force measured at different times of meat aging, backfat thickness, ribeye muscle area, scanning parameters [lightness, redness (a*), and yellowness] to ascertain color characteristics of meat and fat, water-holding capacity, cooking loss (CL), and muscle pH were conducted using genotype data from the Illumina BovineHD BeadChip array to identify quantitative trait loci (QTL) in all phenotyped Nelore cattle. Phenotype count for these animals ranged from 430 to 536 across traits. Meat quality traits in Nelore are controlled by numerous QTL of small effect, except for a small number of large-effect QTL identified for a*fat, CL, and pH. Genomic regions harboring these QTL and the pathways in which the genes from these regions act appear to differ from those identified in taurine cattle for meat quality traits. These results will guide future QTL mapping studies and the development of models for the prediction of genetic merit to implement genomic selection for meat quality in Nelore cattle.

Resistance of beef cattle of two genetic groups to ectoparasites and gastrointestinal nematodes in the state of São Paulo, Brazil.

The resistance to infestations by ectoparasites and infections by gastrointestinal nematodes was studied in 45 animals (males and females) of two genetic groups: purebred Nelore (NI, n=28) and Three-Cross (1/2 Angus+1/4 Canchim+1/4 Nelore - TC, n=17). The animals were monitored for 24 months, during which they were left to graze in tropical pastures without receiving treatment for parasites. Each month the animals were examined for infestations by external parasites, to count the numbers of cattle ticks Rhipicephalus microplus with diameter greater than 4.5mm present on the left side, horn flies (Haematobia irritans) present in the lumbar region and botfly larvae (Dermatobia hominis) present on the entire body. The H. irritans counts were performed with the aid of digital photographs. At the time of examination, fecal samples were collected to count the eggs per gram (EPG) and to perform coprocultures, and peripheral blood samples were drawn to determine the packed cell volume (PCV) and to count the eosinophils. For statistical analysis, the count data were transformed into log10 (n+1), where n is the number of parasites. For PCV, significant effects (P<0.05) were found for collection month (CO), genetic group (GG) and gender (SX), with means and respective standard errors of 41.5 ± 0.65% for the NI animals, 39.3 ± 0.83% for the TC, 41.5 ± 0.72% for the females and 39.3 ± 0.77% for the males. Regarding the eosinophil counts, only the effect of sex was significant (P<0.01), with means and respective standard errors of 926.0 ± 46.2/µL, for males and 1088.0 ± 43.8/µL of blood, for females. The NI animals presented lower mean counts for all the external parasites compared to the TC animals (P<0.01). For ticks, the transformed means followed by standard errors for the NI and TC animals were 0.06 ± 0.01 and 0.34 ± 0.02, while for horn flies these were 0.92 ± 0.05 and 1.36 ± 0.06 and for botfly larvae they were 0.05 ± 0.03 and 0.45 ± 0.05, respectively. The average EPG values were only influenced by CO (P<0.01). The coprocultures revealed the presence of the following endoparasites: Haemonchus spp., Cooperia spp., Oesophagostomum spp. and Trichostrongylus spp., the last in smaller proportion. There were no significant differences between the genetic groups for the endoparasite loads, except for Cooperia spp., which were present in greater number (P<0.05) in the NI group. The results obtained in this experiment confirm previous findings of greater susceptibility of the Nelore breed to Cooperia spp. and high resistance to ectoparasites.

Genetic parameter estimates and principal component analysis of breeding values of reproduction and growth traits in female Canchim cattle.

Phenotypic data from female Canchim beef cattle were used to obtain estimates of genetic parameters for reproduction and growth traits using a linear animal mixed model. In addition, relationships among animal estimated breeding values (EBVs) for these traits were explored using principal component analysis. The traits studied in female Canchim cattle were age at first calving (AFC), age at second calving (ASC), calving interval (CI), and bodyweight at 420 days of age (BW420). The heritability estimates for AFC, ASC, CI and BW420 were 0.03±0.01, 0.07±0.01, 0.06±0.02, and 0.24±0.02, respectively. The genetic correlations for AFC with ASC, AFC with CI, AFC with BW420, ASC with CI, ASC with BW420, and CI with BW420 were 0.87±0.07, 0.23±0.02, -0.15±0.01, 0.67±0.13, -0.07±0.13, and 0.02±0.14, respectively. Standardised EBVs for AFC, ASC and CI exhibited a high association with the first principal component, whereas the standardised EBV for BW420 was closely associated with the second principal component. The heritability estimates for AFC, ASC and CI suggest that these traits would respond slowly to selection. However, selection response could be enhanced by constructing selection indices based on the principal components.

Candidate genes for production traits in Nelore beef cattle.

Meat quality is an important trait for the beef industry. Backfat thickness, ribeye area, and shear force are traits measured late in life, and the investigation of molecular markers associated with these traits can help breeding programs. In cattle, some polymorphisms have been related to production traits. Thus, the purpose of this study was to assess the presence of polymorphisms in the candidate genes insulin-like growth factor 1 (IGF1), fatty acid-binding protein 4 (FABP4), and peroxisome proliferative active receptor gamma coactivator 1 A (PPARGC1A) and associate them with production traits in reference families of Nelore cattle. We used 270 steers descendent from 20 sires that were chosen to represent variability in this breed. The investigation of marker effects on the traits was performed using a mixed model under the restricted maximum likelihood method. A significant allele substitution effect was found for IGF1 and yearling weight (P ≤ 0.017). The mean allele substitution effect was 6.9 kg, with the 229 allele associated with reduced yearling weight in this Nelore population.

A SNP in ASAP1 gene is associated with meat quality and production traits in Nelore breed.

The ASAP1 gene is located in a QTL region for meat production traits and to access the role of the ASAP1 gene, the association between a SNP in this gene and production traits in beef cattle was studied. For this, about 270 steers of reference families of Nelore breed were used. The investigation of marker effects on the traits was performed using a mixed model under the restricted maximum likelihood method. Novel association of a SNP in the ASAP1 gene and shear force measured at 24 h post mortem (P≤0.0083) was described in this population of Nelore cattle. This polymorphism accounted for 1.13% of the total additive variance and 17.51% of total phenotypic variance of the trait, suggesting that this marker could be used in marker assisted selection.

Genetic associations between weight at maturity and maturation rate with ages and weights at first and second calving in Canchim beef cattle.

Genetic parameters for weight at maturity (WM), maturation rate (MR), age and weight at first calving (AFC and WFC) and second calving (ASC and WSC) were estimated for females of the Canchim breed. The number of records per trait ranged from 1440 to 1923. The restricted maximum likelihood method was used and the statistical model included the fixed effect of contemporary group and the additive genetic and residual as random effects. The mean heritability estimate and respective standard errors were 0.34±0.05 (WM), 0.13±0.04 (MR), 0.14±0.04 (AFC), 0.44±0.06 (WFC), 0.16±0.06 (ASC) and 0.39±0.06 (WSC). The heritability estimate for WM and MR suggested that it would be possible to achieve changes in the animals' growth curve through selection, but the genetic correlation between these two traits suggested that there would be antagonism between them. Selection for WM would result in animals with later growth and would also affect individuals' sexual precocity. This was also seen from the genetic correlations between WM and the other traits, which ranged from 0.37 to 0.98; and between MR and the other traits, which ranged from -0.83 to -0.25. Selection to modify WM would be expected to result in correlated responses in AFC, WFC and WSC and a moderate response in ASC. Although the heritability estimate for MR was low, selection aimed for its increase might cause a large decrease in AFC, ASC and WFC and a moderate change in WSC, and this could be an alternative for improving the progeny's overall performance.

Whole-genome analysis for backfat thickness in a tropically adapted, composite cattle breed from Brazil.

Backfat thickness affects the preservation of the beef carcass after slaughter and confers organoleptic characteristics assessed by the consumer. One of the breeding goals for Canchim, a tropically adapted breed, is to comprehensively increase fat thickness. Our goals were to identify genomic regions associated with backfat in Canchim populations and validate the association of single nucleotide polymorphisms (SNPs) overlapping previously identified QTL regions known to affect fat deposition. Fifteen animals with lower and 15 animals with higher residues for backfat, according to a linear model using the SAS GLM procedure, were selected from a population of 1171 animals and genotyped using the BovineSNP50 BeadChip. Initial analysis revealed more than 100 SNPs that discriminated the tails of phenotypic distribution. One extended region of association included the centromeric region of chromosome (Chr) 14. Because this region overlapped with QTL from previous reports, we developed SNP assays to interrogate two linkage disequilibrium blocks, one in the centromeric region and another in the middle region of Chr 14 to confirm the association. The analysis validated the presence of specific haplotypes affecting fat thickness.

Resistance of cattle of various genetic groups to the tick Rhipicephalus microplus and the relationship with coat traits.

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 log(10) (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 cm(2) (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).

Candidate gene region for control of rib eye area in Canchim beef cattle.

Investigation of molecular marker effects on production traits is essential to define marker assisted selection strategies in beef cattle. We looked for a possible association of molecular markers and backfat thickness (BFT) and rib eye area (REA) in Canchim (5/8 Charolais + 3/8 Zebu) and MA (offspring of Charolais bulls and 1/2 Canchim + 1/2 Zebu cows) animals raised exclusively on pasture. Traits were measured on 987 individuals from seven herds from two Brazilian States (São Paulo and Goiás), in March and April from 2005 to 2007, when animals were, on average, 19 months of age. Five microsatellite markers lying in QTL regions for BFT and REA (BMS490 and ETH10 on chromosome 5, INRA133 and ILSTS090 on chromosome 6, and BMS2142 on chromosome 19) were genotyped and association analyses were performed under an animal model using the restricted maximum likelihood method. After correction for multiple tests, a significant effect of microsatellite BMS490 on REA was observed, suggesting that at least one QTL affecting carcass traits in this region of the BTA5. No significant effect on BFT was observed for these markers.

Genotype × environment interaction for long-yearling weight in Canchim cattle quantified by reaction norm analysis.

The objective of this study was to investigate the presence of genotype × environment interactions (G×E) for long-yearling weight in Canchim cattle (5/8 Charolais + 3/8 zebu) in Brazil using reaction norms (RN). The hierarchical RN model included the fixed effect of age of the animal (linear coefficient) and random effects of contemporary groups and additive animal genetic intercept and slope of the RN and contemporary group effects as random effects. Contemporary groups as the most elemental representation of management conditions in beef cattle were chosen to represent the environmental covariate of the RN. The deviance information criteria demonstrated that a homoskedastic residual RN model provided a better data fit compared with a heteroskedastic counterpart and with a traditional animal model, which had the worst fit. The environmental gradient for long-yearling weight based on contemporary group effects ranged from -105 to 150 kg. The additive direct variance and heritability estimates increased with increasing environmental gradient from 74.33 ± 22.32 to 1,922.59 ± 258.99 kg(2) and from 0.08 ± 0.02 to 0.68 ± 0.03, respectively. The high genetic correlation (0.90 ± 0.03) between the intercept and the slope of the RN shows that animals with the greatest breeding values best responded to environmental improvement, characterizing scale effect as the source of G×E for long-yearling weight. The phenotypic plasticity demonstrated by the slope of the RN of the animal indicates the possibility to change genotype expression along the environmental gradient through selection. The results demonstrate the importance of accounting for G×E in the genetic evaluation of this population.