Crossbreeding applied to systems of beef cattle production to improve performance traits and carcass quality.

Crossbreeding represents an important technique to improve growth, beef quality and adaptability in beef production systems in tropical countries. The aim of this study was to evaluate sire and dam breed effects on performance and carcass traits of crossbred cattle produced in a tropical environment. Heifers and steers were evaluated during the pre-weaning, the post-weaning (n = 173) and the finishing phase (n = 123). Animals were produced by mating Nellore (N_N), Angus × Nellore (A_N) and Caracu × Nellore (C_N) dams with Braford, Charbray and Caracu sires. After weaning, animals were raised grazing on Marandu grass for 12 months; thereafter they were housed in individual pens and finished in a feedlot, receiving a total mixed ration. Ultrasound carcass evaluations were performed to determine ribeye area (R_A), backfat thickness (B_T) and rump fat thickness (R_T). A_N progeny were heavier at birth than N_N (P < 0.05), and Braford progeny had greater birth BW than Caracu (P < 0.05). Greater weaning BW was observed in the A_N and C_N offspring compared to N_N (P < 0.01). Greater average daily gain during the post-weaning period was verified in the N_N progeny compared to C_N (P < 0.05). No dam or sire breed effects were observed for BW at the end of the post-weaning period (P > 0.05). Progeny of N_N cows had greater B_T (P < 0.05) and R_T (P < 0.01) at the end of the post-weaning period in relation to C_N. Greater R_A was observed in the Caracu progeny than in the Braford (P < 0.05), which showed greater R_T than the Charbray progeny at the end of the post-weaning period (P < 0.05). No dam or sire breed effects were verified for final BW at the feedlot or for feed efficiency traits (P > 0.05). A_N progeny were superior in final B_T compared to C_N (P < 0.01), and Braford progeny had greater R_T at the end of finishing than Charbray (P = 0.05). The use of crossbred dams allows an increase in productivity until weaning, but this is not maintained in the post-weaning and finishing periods. The use of Braford sires produces similar growth performance in the different stages of the production system to those seen with Charbray and Caracu sires but generates animals with higher fat thickness at the end of finishing, which may improve carcass quality and commercial value.

Transcriptome changes in muscle of Nellore cows submitted to recovery weight gain under grazing condition.

The aim of this study was to evaluate transcriptome changes in the muscle tissue of Bos taurus indicus cull cows subjected to recovery weight gain under grazing conditions. In all, 38 Nellore cull cows were divided randomly into two different management groups: (1) Maintenance (MA) and (2) Recovery gain (RG) from weight loss by moderate growth under high forage availability. After slaughter, RNA analysis was performed on the Longissimus thoracis muscle. Semaphorin 4A, solute carrier family 11 member 1, and Ficolin-2 were expressed in the RG, which may indicate an inflammatory response during tissue regrowth. Signaling factors, such as Myostatin, related to fibroblast activation, negative control of satellite cell proliferation in adults and muscle protein synthesis were less abundant in the RG group. The only gene related to anabolic processes that were more abundant in the MA group was related to fat deposition. The genes that were differentially expressed in the experiment showed muscle repair-related changes during RG based on the greater expression of genes involved in inflammatory responses and the lower expression of negative regulators of muscle cell proliferation and hypertrophy.

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.

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.

Quantitative and qualitative carcass characteristics of feedlot ewes subjected to increasing levels of concentrate in the diet / Características quantitativas e qualitativas da carcaça de borregas confinadas submetidas a níveis crescentes de concentrado na dieta

The aim of this study was to evaluate the effect of increasing levels of concentrate on the quantitative and qualitative carcass characteristics of feedlot ewes. Twenty-four crossbred ewes were randomly distributed in four treatments: (1) diet with 20%; (2) 40%; (3) 60%; and (4) 80% of concentrate. Animals were slaughtered when those receiving the diet with 80% of concentrate reached adult weight, at around 50kg LW. The data were analyzed by means of variance and regression analyses and correlations. The levels of concentrate increased live weight at slaughter linearly. Height at the withers and rump presented medium to high correlation (0.86). The correlation of loin eye area measured on the carcass and by ultrasound examination was 0.81, whereas for back fat thickness it was 0.85. The increase in the use of concentrate in the diets promotes heavier carcasses with better yields and fat cover. Some measures obtained in vivo presented high correlation with those measured on the carcass. The use of ultrasound can be a way to predict the in vivo loin eye area. The use of concentrate improves the meat quality in variables' color and appearance...

Objetivou-se avaliar o efeito de níveis crescentes de concentrado sobre as características quantitativas e qualitativas de carcaça de borregas confinadas. Vinte e quatro borregas mestiças foram aleatoriamente distribuídas em quatro tratamentos: (1) dieta com 20%; (2) 40%; (3) 60% e (4) 80% de concentrado. Os animais foram abatidos quando os que recebiam a dieta 80% de concentrado atingiram o peso adulto, ao redor de 50kg PV. Os dados foram analisados por meio de análise de variância e regressão e de correlações. Os níveis de concentrado aumentaram linearmente o peso vivo ao abate. A altura de cernelha e de garupa apresentaram correlação média a alta (0,86). A correlação da área de olho de lombo medida na carcaça e por meio de ultrassom apresentou valor de 0,81, enquanto a espessura de gordura subcutânea foi de 0,85. O aumento do uso de concentrado nas dietas proporciona carcaças pesadas e com melhores rendimentos e acabamentos. Algumas medidas feitas in vivo apresentaram alta correlação com as medidas na carcaça. O uso do ultrassom pode ser utilizado como forma de predição da área de olho de lombo in vivo. O uso do concentrado melhora a qualidade da carne nos parâmetros de cor e aparência...

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.

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.