The Nellore breed was spread in Brazil into the half of 20th century fromIndia. At the begging of the decade 2000, the Nellore breed represented around 80% ofthe national beef cattle herd. The advantage of the zebu breed, as Nellore, is due to theirability to adapt to tropical weather. In the second half of the 20th century, successfulnational genetic improvement programs started to select animals with better productiveand reproductive characteristics, such as weight gain and scrotal circumference, amongothers that are easy to measure. During the last years, together with the use of genomictools and more accurate phenotype evaluation techniques, it has been seen theimplementation of the improvement of characteristics related to the productive and earlyreproductive, as well as the quality of the carcasses and cuts. In addition, severalnutritional management and protocols started to be tested and applied to Nellore cattlein different growth phases. These managements aim, directly or indirectly, to changecharacteristics related to meat quality. Between some of the management, the earlyweaning, that consists of calves weaning between 60 and 120 days old, which helped inimproving the reproductive efficiency of the dam, also in Taurus breed, the researchshowing the change in early weaning calves' metabolism, as fat deposition andproportion of muscle fiber type. These changes occurred due tometabolic imprinting, which can alter the muscle tissue development and lipiddeposition during this phase. In this sense, the objective of this work will be to evaluatethe differential expression of genes related to muscle fiber metabolism in Nellore calvessubmitted to different weaning protocols. For this, will be used 10 animals submitted atearly weaning (120 days) and 10 animals submitted at conventional weaning (210 days).The animals from early weaning will be fed with concentrate in feedlot and the calvesfrom conventional will be kept with their dam in the pasture until 210 days. The RNA-seq method will be performed for sequencing the total messenger RNA from samplescollected from calf's Longissimus thoracis using both groups at 210 days. Afterwards,the sequences obtained (reads) will be aligned to the reference genome and, finally, thedifferentially expressed genes will be detected using the R program edgeR package. Theresults will be filtered according to the gene function and participation of metabolicpathways concerning the metabolism of skeletal muscle fibers. The results of this studywill bring important information about adaptations in muscle metabolism of calvessubmitted to different postpartum diets.
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