In cattle, as in other species, environmental influences in the postnatal period,such as climate, diet and stress, can have a strong impact on their adult life due toimportant metabolic changes at this phase of development. In this sense, changes inpostnatal management could alter the performance of animals and the quality of productsin beef cattle. Among the molecular mechanisms involved in these metabolic changes isepigenetics, highly modulated during this period through changes in the DNA packagingstructure and in the DNA structure itself, as in the case of cytosine methylation. Amongcommercial managements useful in the breeding phase of beef cattle, there is earlyweaning, which, although it aims at the reproductive improvement of females by notexpending more energy for suckling, can significantly alter the metabolism of weanedcalves due to the supply of concentrated diet. The supply of quality nutrition at thebeginning of the animal's life can lead, as seen in Bos taurus, to changes in fatty acidmetabolism, muscle fiber differentiation, among other metabolic pathways that directlyaffect the quality of the final product. The Nellore zebu breed has poor productive andreproductive rates compared to taurine breeds, although it has greater robustness andtolerance to parasites, which makes it widely bred in Brazil, with a tropical climate.Studies aimed at understanding metabolic adaptations due to management during thebreeding phase are scarce with Zebu breeds and non-existent with Nellore breeds. Fromthis, the objective of this study will be to describe DNA methylation patterns in genepromoter regions of the skeletal striated muscle of Nellore calves before and after earlyweaning, at 120 and 210 days, respectively. For this, 20 calves weaned at 120 days of ageand which remained in semi-confinement until 210 days of age will be used. These animalsreceived a diet containing 20% CP, 75% TDN in the period. Aliquots of muscle from thelumbar region (Longissimus thoracis) were collected by means of biopsy at 120 and 210days. Five animals will be chosen of total 20 initial animals, which had their DNAextracted from muscle tissue aiming at bisulfite sequencing of previously enriched portionsof the genome by means of restriction enzyme (MspI). The sequencing data will bepreviously submitted to analysis and quality control of the readings obtained using FastQCand FastP software. Afterwards, through the Bismark and Bowtie2 program, the readingsthat will undergo quality control will be indexed and aligned. The methylation status of allcytosine positions in the sequences will be inferred using the methylation_extractorfunction of the Bismark program. At each site (nucleotide), the methylation rate may varyfrom 0% to 100%. From this, a broad descriptive analysis of the epigenetic changes will beperformed for each of the collection moments. Thus, it is expected to obtain important andunprecedented results of characterization of DNA methylation of muscle tissue of Nellorecalves submitted to early weaning, contributing to the growth of knowledge in the area.
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