Genetic parameters for traditional and novel ultrasound carcass traits in Nellore cattle.

The objective of this study was to contribute to genetic improvement for carcass quality in Nellore cattle by estimating genetic parameters for carcass characteristics measured by traditional and novel ultrasound adjusted for body weight. Records of 19,910 Nellore breed animals born between 2001 and 2015 as part of a genetic improvement program were evaluated for this purpose. The (co)variance components and genetic parameters for yearling weight (YW), slaughter conformation at yearling age (SCY), ribeye area (REA), REA adjusted for 100 kg of body weight (REA100), REA adjusted for 450 kg of body weight (REA450), subcutaneous fat thickness over the loin (SFTL) and the rump (SFTR), intramuscular fat (IF), and height × width ratio of the sirloin steak (RATIO) were estimated using the restricted maximum likelihood (REML) method and the three-trait animal model. The estimated heritability values were 0.39 (YW), 0.33 (SCY), 0.31 (REA), 0.42 (REA100), 0.38 (REA450), 0.31 (RATIO), 0.17 (SFTL), 0.27 (SFTR), and 0.41 (MAR). The genetic correlations between REA and YW (0.43) and SCY and YW (0.78), respectively, suggested that selecting for REA or SCY could result in an increase in body weight. Because of its moderate and negative correlation with YW, REA100 was ineffective as a muscling indicator (- 0.38). The indicators REA450 and RATIO had a - 0.12 and 0.11 low correlation with YW, respectively. Thus, it is concluded that REA450 and RATIO were the best indicators of muscling, with heritability of medium magnitude, making the selection viable, as well as having a low correlation with body weight.

Development of tetra-primer ARMS-PCR protocol to genotype the prolactin receptor SNP 39136666 and assessment of this SNP in Brazilian locally adapted cattle breeds / [Desenvolvimento de protocolo de tetra-primer ARMS- PCR para genotipagem do SNP 39136666 do receptor da prolactina e avaliação desse SNP em raças bovinas brasileiras localmente adaptadas]

As raças taurinas de origem ibérica Limonero e Carora (Bos primigenius taurus) possuem o fenótipo de pelo curto, liso e com baixa densidade folicular, o que confere a esses animais maior tolerância térmica e melhor produtividade em regiões quentes. Diferentes mutações associadas a esse fenótipo foram descritas no gene do receptor de prolactina PRLR, localizado no cromossomo bovino BTA20. Uma mutação recentemente encontrada é a substituição do nucleotídeo C por T, SNP 39136666 (p. R497*), no exon 11, que gera um códon de parada e, consequentemente, uma menor isoforma desse receptor. Neste trabalho, desenvolveu-se um protocolo rápido e de baixo custo para detecção desse SNP, utilizando-se a técnica de tetra-primer ARMS-PCR. Assim, foi possível detectar essa mutação nas raças brasileiras de origem ibérica localmente adaptadas: Caracu, Crioulo Lageano, Mocho Nacional e Pantaneiro. O alelo T foi mais frequente na raça Caracu (80%), enquanto o alelo C foi mais frequente na raça Crioulo Lageano (84%). Essa simples metodologia pode ser usada para genotipar esse SNP e ajudar na aplicação dessas informações moleculares em programas de melhoramento focados na tolerância térmica em bovinos taurinos e seus mestiços.(AU)

Water requirements of beef production can be reduced by genetic selection.

Growing concerns regarding sustainability in agriculture include the availability of drinking water, which is putting pressure on livestock production, especially the beef sector, for more efficient practices. Thus, genetic parameters were estimated for traits related to water intake and water use efficiency in Senepol cattle. Senepol females (n = 925) and males (n = 191) were evaluated in performance tests carried out from 2014 to 2019. Daily dry matter intake (DMI) and water intake (WI) were recorded by electronic feed and water bunks (Intergado Ltd.). Other traits assessed included average daily gain (ADG); mid-test metabolic BW (BW0.75); residual water intake based on ADG (RWIADG), estimated as the residual of the linear regression equation of WI on ADG and BW0.75; residual water intake based on DMI (RWIDMI), estimated as the residual of the linear regression equation of WI on DMI and BW0.75 (RWIDMI); water conversion ratio (= WI/ADG); gross water efficiency (GWE = ADG/WI); residual feed intake estimated as the residual of the linear regression equation of DMI on ADG and BW0.75 (RFI); feed conversion ratio (= DMI/ADG) and gross feed efficiency. Genetic (co)variances were estimated with bivariate analyses. The heritabilities for WI, RWIADG and RWIDMI were 0.38, 0.36 and 0.33, respectively. Water conversion ratio, RWIADG and RWIDMI showed positive genetic and phenotypic correlations with WI, whereas GWE was negatively correlated with WI, suggesting that traits related to water use efficiency may be useful to identify cattle with reduced WI. Water intake showed positive genetic (r = 0.79) and phenotypic (r = 0.60) correlations with DMI, suggesting the use of WI to estimate DMI in future studies. Both RWIADG and RWIDMI were genetically correlated with RFI (0.67 and 0.57, respectively) and ADG (0.49 and 0.44, respectively), showing that RWI is positively associated with feed efficiency, but has an antagonistic relationship with growth. This antagonism, however, may be managed using selection indexes. Genetic improvement of water use efficiency in Senepol cattle is possible through selection and may reduce the water requirements of beef production systems.

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)

Identification and evaluation of polymorphisms in FABP3 and FABP4 in beef cattle.

Single nucleotide polymorphisms (SNPs) were screened in FABP3 and FABP4 by automatic sequencing of pools of DNA from crossbred animals whose phenotypes belonged to the upper and lower extremes for back fat and marbling, as well as of a pool of DNA from sires used for crossbreeding. Five SNPs were identified in FABP3 and another nine SNPs were identified in FAPB4. Of these, only one SNP had no previous registry in the SNAP database (dbSNP). Three polymorphisms were selected for further evaluation of their association with production traits using restriction fragment length polymorphism-PCR (RFLP-PCR) or real-time PCR genotyping. All 3 markers were in Hardy-Weinberg equilibrium at the 5% significance level for all 7 genetic groups analyzed. Significant association was observed between FABP3-G/A with rib eye area (P = 0.035) and the rib eye area/hot carcass weight ratio (P = 0.025) and between FABP4/TasI with marbling (P = 0.052) and meat texture (P = 0.053). No significant association was observed between the FABP4-G/C polymorphism and any of the observed traits. Previous association studies with allelic variants in these genes have shown mixed results, probably because of the small effect of the genes for these traits, which suggests that results should be replicated in other populations.

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.

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.

Ácidos graxos voláteis no rúmen de vacas alimentadas com diferentes teores de concentrado na dieta / Volatile fatty acids in rumen of cows fed different concentrate level diets

Avaliou-se o efeito de teores de concentrado na dieta sobre a concentração de ácidos graxos voláteis no líquido ruminal de bovinos. Foram utilizadas quatro vacas mestiças, fistuladas no rúmen, com peso médio de 442,15kg, distribuídas em quadrado latino 4x4, divididos em quatro períodos de 14 dias, sendo 11 de adaptação e três para coleta de dados. Foi utilizada a silagem de milho, como volumoso, e milho, sorgo, farelo de soja, casca de soja, ureia e gordura protegida, como concentrado. As dietas foram formuladas para 13 por cento de proteína bruta (PB), utilizando-se proporções de 30; 40; 50 e 60 por cento de concentrado. Não houve influência do tratamento para concentrações de ácido acético, isobutírico, butírico, isovalérico e valérico. O ácido propiônico e a proporção acetato:propionato apresentaram concentrações máximas em 8,44 e 8,14 horas após a alimentação, respectivamente. Os ácidos graxos totais não foram influenciados pelos tratamentos, com concentração máxima em 7,68 horas após a alimentação, juntamente com valores mínimos de pH entre seis e nove horas. Dietas com até 60 por cento de concentrado na matéria seca total não influenciaram as concentrações de ácidos graxos voláteis do rúmen.

The influence of concentrate levels from the diet on the content of volatile fatty acids in rumen fluid of cattle was evaluated. Four rumen fistulated crossbred cows, weighting around 442.15kg, were distributed in 4x4 Latin square schedule, divided into four periods of 14 days, 11 for adaptation and three for data collection. Corn silage was used as roughage, and corn, sorghum, soybean meal, soybean hulls, protected fat and urea, as concentrate. Diets were formulated with 13 percent crude protein (CP), using the proportions of 30, 40, 50 and 60 percent concentrate. There was no influence of treatment for the following acid concentrations: acetic, isobutyric, butyric, isovaleric and valeric. The propionic acid content and the ratio acetate: propionate showed values of 8.44 and 8.14 hours after feeding, respectively. The total fatty acids were not affected by treatments, with maximum concentration at 7.68 hours after feeding, with minimum pH values between six and nine hours. Diets containing up to 60 percent of concentrate in dry matter did not influence the concentrations of rumen volatile fatty acids.

Random regression models using different functions to model test-day milk yield of Brazilian Holstein cows.

We analyzed 152,145 test-day records from 7317 first lactations of Holstein cows recorded from 1995 to 2003. Our objective was to model variations in test-day milk yield during the first lactation of Holstein cows by random regression model (RRM), using various functions in order to obtain adequate and parsimonious models for the estimation of genetic parameters. Test-day milk yields were grouped into weekly classes of days in milk, ranging from 1 to 44 weeks. The contemporary groups were defined as herd-test-day. The analyses were performed using a single-trait RRM, including the direct additive, permanent environmental and residual random effects. In addition, contemporary group and linear and quadratic effects of the age of cow at calving were included as fixed effects. The mean trend of milk yield was modeled with a fourth-order orthogonal Legendre polynomial. The additive genetic and permanent environmental covariance functions were estimated by random regression on two parametric functions, Ali and Schaeffer and Wilmink, and on B-spline functions of days in milk. The covariance components and the genetic parameters were estimated by the restricted maximum likelihood method. Results from RRM parametric and B-spline functions were compared to RRM on Legendre polynomials and with a multi-trait analysis, using the same data set. Heritability estimates presented similar trends during mid-lactation (13 to 31 weeks) and between week 37 and the end of lactation, for all RRM. Heritabilities obtained by multi-trait analysis were of a lower magnitude than those estimated by RRM. The RRMs with a higher number of parameters were more useful to describe the genetic variation of test-day milk yield throughout the lactation. RRM using B-spline and Legendre polynomials as base functions appears to be the most adequate to describe the covariance structure of the data.

Correlation between fertility and levels of protein, sugar and free amino acids in seminal plasma of Nelore bulls

Estimaram-se as correlações entre fertilidade e concentrações de proteínas, açúcares redutores e 17 tipos de aminoácidos livres do plasma seminal de 19 touros Nelore, adultos, doadores de sêmen de alta qualidade segundo as análises físicas e morfológicas. O escore de fertilidade foi estimado de acordo com a porcentagem de gestação das fêmeas cobertas em três estações de monta consecutivas, por inseminação artificial ou monta natural. Foi observada alta variabilidade na concentração das moléculas analisadas nas amostras. O coeficiente de correlação estimado entre concentrações de proteína e de açúcares redutores foi de 0,90. Individualmente, nenhum dos componentes quantificados apresentou correlação significativa com a fertilidade dos touros.

Analyses of growth curves of Nellore cattle by Bayesian method via Gibbs sampling

Growth curves of Nellore cattle were analyzed using body weights measured at ages ranging from 1 day (birth weight) to 733 days. Traits considered were birth weight, 10 to 110 days weight, 102 to 202 days weight, 193 to 293 days weight, 283 to 383 days weight, 376 to 476 days weight, 551 to 651 days weight, and 633 to 733 days weight. Two data samples were created: one with 79,849 records from herds that had missing traits and another with 74,601 from herds with no missing traits. Records preadjusted to a fixed age were analyzed by a multiple trait model (MTM), which included the effects of contemporary group, age of dam class, additive direct, additive maternal, and maternal permanent environment. Analyses were carried out by a Bayesian method for all nine traits. The random regression model (RRM) included the effects of age of animal, contemporary group, age of dam class, additive direct, permanent environment, additive maternal, and maternal permanent environment. Legendre cubic polynomials were used to describe random effects. MTM estimated covariance components and genetic parameters for birth weight and sequential weights and RRM for all ages. Due to the fact that covariance components based on RRM were inflated for herds with missing traits, MTM should be used and converted to covariance functions.