Abstract This study evaluated the effects of rumen-protected metabolizable methionine (RPM) supplementation on performance, carcass traits, ruminal morphometry, cecal histology, and meat quality of crossbred heifers finished on Urochloa brizantha pastures during the rainy-to-dry seasonal transition. Forty-eight 18-month-old ½ Nellore × ½ Angus heifers (380 ± 44 kg) were assigned to three supplementation strategies: a control treatment (T1) receiving an energy–protein supplement without methionine; T2 receiving the same supplement plus 3 g/animal per day of RPM; and T3 receiving 3 g/day of RPM combined with a more gradual increase in concentrate supplementation over the 140-day grazing period. RPM supplementation did not affect final body weight or average daily gain throughout the experimental period. However, heifers receiving RPM supplementation (T2 and T3) showed greater ribeye area and lower Biceps femoris fat thickness than the control treatment. Ruminal morphometry revealed a greater number of papillae in RPM-supplemented animals, although absorptive surface area and other ruminal histological measurements were not affected by treatment. In the cecum, the most pronounced responses were observed in T3, which showed lower lesion scores and fewer goblet and disrupted goblet cells than the other treatments. Meat quality evaluations indicated greater marbling scores in RPM-supplemented heifers without changes in tenderness or cooking loss. In conclusion, RPM supplementation was associated with changes in carcass traits, ruminal morphometric variables, and cecal histological responses in grazing beef heifers under tropical conditions. The most pronounced cecal responses occurred in the treatment combining RPM supplementation with gradual concentrate adaptation, although the experimental design does not allow complete separation of the effects of methionine supplementation and feeding-management strategy.
Lelis et al. (Wed,) studied this question.