Impact of weight recovery on transcriptome and meat phenotypes of adult Nellore cows

<p>The speed of renewal of muscle proteins defines muscle growth, and can affect meat quality, as well as collagen turnover and proteolytic rate. There is little information in the literature about changes in the muscle protein remodeling process in response to the rate of recovery of weight gain after malnutrition in adult animals. The use of RNA sequencing may indicate changes in muscle tissue through a differential expression profile that explains changes in phenotypes associated with muscle growth. Therefore, the objective of this study was to evaluate changes in the transcriptome associated with phenotypes of meat of Nellore adult cows submitted to different rates of weight recovery. In this experiment, 28 adult cows aged 5 to 16 years were used. With the exception of 5 animals, the others had low body score and were randomized into 3 groups: T1-Control animals (slaughtered with low body score, n=4); T2-Slow weight gain (0.6kg/day, n=9); T3 - Accelerated weight gain (1.2 kg/day, n=10). The group T4-Maintenance of body weight (animals with high body score, kept in confinement until the end of the experiment, n=5), were allocated the other animals. The animals were slaughtered in 4 periods (S1=T1; S2=T2 and T3; S3=T3; S4=T2 and T4), and <i>Longissimus</i> muscle samples were collected to obtain the total RNA. After obtaining the RNA and preparation of the libraries, the sequencing of the samples was done in a HiScanSQ equipment. Twenty-four hours after slaughter, the pH and instrumental color (L*, a*, b*) were measured in the <i>Longissimus</i> muscle, and 2 steaks were collected for shear force analysis at 24h and 21 days. For comparisons of the phenotypes and genes, contrasts were made using the T1 group as a reference. Statistical differences between treatments were analyzed in R software, using ANOVA and Tukey test. There were significant (P<0.05) changes in shear force at 21 days in the group T2 (S4) e T4 (S4) and values L*, a*, b* in the T3 group (S3). Seven differentially expressed genes were found in both contrasts analyzed, D-aspartate oxidase (DDO), Serpin family H member 1 (SERPINH1), Neural precursor cell expressed, developmentally down-regulated 4 (NEDD4), novel gene (ENSBTAG00000030593), Collagen type IV alpha 1 chain (COL4A1), Activating transcription factor 5 (ATF5), and the novel gene (ENSBTAG00000018451). The differences found between phenotypes and genes indicate that growth rates impact differently on the phenotypes associated with meat quality. In addition, it is possible to state that feedback in adult animals may be an alternative to improving quality of meat, since some differentially expressed genes are associated with important modifications in muscle.</p>