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BackgroundThe selection of beef cattle for feed efficiency (FE) traits is very important not only for productive and economic efficiency but also for reduced environmental impact of livestock. Considering that FE is multifactorial and expensive to measure, the aim of this study was to identify biological functions and regulatory genes associated with this phenotype.ResultsEight genes were differentially expressed between high and low feed efficient animals (HFE and LFE, respectively). Co-expression analyses identified 34 gene modules of which 4 were strongly associated with FE traits. They were mainly enriched for inflammatory response or inflammation-related terms. We also identified 463 differentially co-expressed genes which were functionally enriched for immune response and lipid metabolism. A total of 8 key regulators of gene expression profiles affecting FE were found. The LFE animals had higher feed intake and increased subcutaneous and visceral fat deposition. In addition, LFE animals showed higher levels of serum cholesterol and liver injury biomarker GGT. Histopathology of the liver showed higher percentage of periportal inflammation with mononuclear infiltrate.ConclusionLiver transcriptomic network analysis coupled with other results demonstrated that LFE animals present altered lipid metabolism and increased hepatic periportal lesions associated with an inflammatory response composed mainly by mononuclear cells. We are now focusing to identify the causes of increased liver lesions in LFE animals.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-2292-8) contains supplementary material, which is available to authorized users.

The current research was conducted to estimate the heritability coefficients and the genetic correlations for performance and carcass and body composition traits in a single sire broiler line. The performance traits analyzed were BW at 38 d, ultrasound records of pectoral muscle depth, feed intake, feed conversion ratio, and BW at 42 d. The carcass traits analyzed were eviscerated BW, breast weight, and leg weight, and the body composition traits analyzed were abdominal fat content, heart weight, gizzard weight, liver weight, and intestine weight. The number of observations varied between 4,120 and 29,040 for each trait. The (co)variance components, heritability, and genetic correlation estimates were obtained by restricted maximum likelihood. The numerator relationship matrix had 42,912 animals. Based on the heritability estimates obtained, the analyzed traits seemed to be able to respond to selection, at variable intensities. The genetic correlation estimates between a great number of performance traits, as well as between a great number of carcass traits, were suggestive of a close genetic relationship between these traits. The genetic correlation estimates between body composition traits were variable. A large genetic association between a great number of performance and carcass traits seemed to exist. The genetic correlation estimates between performance and body composition traits were variable, and important associations between carcass and body composition traits did not seem to exist.

Estimates of (co)variance components and genetic parameters were obtained for birth, 205-d, and 365-d weight for Nelore cattle in Brazil, using single and multiple-trait animal models. Data were from the Brazilian Zebu Breeders Association (ABCZ). Records of 27,549 calves sired by 587 bulls and raised on pasture in 57 herds were analyzed by restricted maximum likelihood fitting an animal model including direct and maternal genetic and permanent environmental effects. Single and multiple-trait analyses were carried out. Heritability estimates for direct effects were lower than previous values reported for the Nelore breed. The estimates for maternal genetic effects showed that the contribution of this component to the phenotypic variance of birth and weaning weight is not very high but is still present at yearling weight. Correlations between direct and maternal additive genetic effects were negative for all traits analyzed except for yearling weight in the single-trait analysis where the sign was positive but the magnitude was small (+.09). Genetic correlations between weaning and yearling weights were .74 (direct effect) and .84 (maternal effect). Permanent environmental and residual correlations among traits were also obtained.

To estimate the heritability for the probability that yearling heifers would become pregnant, we analyzed the records of 11,487 Nellore animals that participated in breeding seasons at three farms in the Brazilian states of São Paulo and Mato Grosso do Sul. All heifers were exposed to a bull at the age of about 14 mo. The probability of pregnancy was analyzed as a categorical trait, with a value of 1 (success) assigned to heifers that were diagnosed pregnant by rectal palpation about 60 d after the end of the breeding season of 90 d and a value of 0 (failure) assigned to those that were not pregnant at that time. The estimate of heritability, obtained by Method R, was 0.57 with standard error of 0.01. The EPD was predicted using a maximum a posteriori threshold method and was expressed as deviations from 50% probability. The range in EPD was -24.50 to 24.55%, with a mean of 0.78% and a SD of 7.46%. We conclude that EPD for probability of pregnancy can be used to select heifers with a higher probability of being fertile. However, it is mainly recommended for the selection of bulls for the production of precocious daughters because the accuracy of prediction is higher for bulls, depending on their number of daughters.