This study evaluated the effects of guanidinoacetic acid (GAA) supplementation during the growing and finishing phases on Nellore bulls’ performance, carcass traits, and meat quality. Fifty-two Nellore bulls were randomly assigned to four treatments: control (CON, without GAA) and three GAA levels (3, 6, and 9 g/kg dry matter [DM] in the growing supplement; 0.3, 0.6, and 0.9 g/kg DM in the finishing diet). During the 280-day growing phase, bulls were kept in paddocks, while in the 74-day feedlot finishing phase, they were housed in collective pens. Body weight, average daily gain, and carcass ultrasound measurements were recorded in both phases. Feed intake was recorded daily during finishing, and carcass traits were evaluated post-slaughter. GAA supplementation during the growing phase did not affect performance or ultrasound carcass traits (p ≥ 0.12). In the finishing phase, increasing GAA doses linearly reduced body weight gain (p = 0.03) without affecting carcass traits assessed by ultrasound or post-slaughter (p ≥ 0.10). GAA supplementation linearly reduced cooking loss (p = 0.02) without influencing other meat quality parameters (p ≥ 0.11). It is concluded that, under the conditions of this study, GAA supplementation did not affect performance or carcass traits, except for reduced weight gain at the highest dose, but reduced water loss from cooked meat.

The objective of this study was to evaluate the in vitro fermentation products, digestibility, gas production (GP) kinetics, and enteric greenhouse emissions (CH4 and CO2) of substrates with different forage:concentrate ratios (100F, grass hay only; 100C, concentrate mixture only, and mixture, an equal proportion of them) within non-woven fabric (NWT; 100 g/m2) or F57 (Ankom®) filter bags compared to directly dispersed in the medium (DIS), arranged in a 3 × 3 factorial arrangement. Substrates (0.5 g) were incubated using [...] ABSTRACT The objective of this study was to evaluate the in vitro fermentation products, digestibility, gas production (GP) kinetics, and enteric greenhouse emissions (CH4 and CO2) of substrates with different forage:concentrate ratios (100F, grass hay only; 100C, concentrate mixture only, and mixture, an equal proportion of them) within non-woven fabric (NWT; 100 g/m2) or F57 (Ankom®) filter bags compared to directly dispersed in the medium (DIS), arranged in a 3 × 3 factorial arrangement. Substrates (0.5 g) were incubated using

This study evaluated the effects of different levels of guanidinoacetic acid (GAA) supplementation on the transcript abundance of genes related to myogenesis, protein turnover, and energy metabolism in Nellore (Bos indicus) cattle during the growing and finishing phases. Fifty-one bulls were supplemented with 0, 3, 6, or 9 g GAA·kg⁻¹ of supplement dry matter (DM) during the growing phase and 0, 0.3, 0.6, or 0.9 g GAA·kg⁻¹ of dietary DM during the finishing phase. Longissimus thoracis samples were collected at the end of each phase for RT-qPCR analyses. During the growing phase, GAA supplementation increased the transcript abundance of genes associated with myogenic regulation (PAX7, MYF5, and MYOG) and anabolic signaling (MTOR and EIF4E), resulting in a transcriptional profile consistent with the modulation of genes involved in myogenic regulation and protein turnover, with responses differing among doses. During the finishing phase, continued GAA supplementation decreased the transcript abundance of MYF5, MYOG, EIF4E, FBXO32, and SLC2A4, whereas MTOR and GSK3B showed positive quadratic responses to increasing GAA doses. However, these molecular responses were not accompanied by improvements in growth performance, carcass characteristics, or most meat quality variables. Differences in gene expression observed at the end of the growing and finishing phases should be interpreted in the context of diet, management, feeding system, and duration of GAA exposure.