EFFECTS OF INCREASING LEVELS OF AN ENERGY SUPPLEMENT ON PRODUCTIVE PERFORMANCE AND BEEF QUALITY OF FINISHING GRAZING STEERS

Resumen

The aim of the study was to assess the effects of increasing levels of an energy supplement on productive performance and the nutritional quality of steers finished on pasture. The supplement consisted of a blend of whole oat grain and steam-rolled corn. Treatments included a Control (steers grazing ryegrass pastures + mineral supplementation) and three increasing levels of the energy supplement corresponding to 0.5, 1.0, and 1.5% of body weight. Pasture nutritional quality was adequate throughout the experimental period, except for energy (< 2.88 MCal ME kg^-1 DM). Daily dry matter intake, body weight, and average daily gain were similar across treatments. However, carcass weight and dressing percentage differed, with lower values observed in the Control group. Steers receiving the 1.0% supplementation level exhibited greater fat cover and a tendency toward greater ribeye area. No treatment effects were observed in meat quality parameters. All samples were classified as tender (Warner-Bratzler Shear Force < 2.3 kgf), and pH was < 5.9. There were differences in the fatty acid profile, particularly in hexadecanoic and margaric acids, as well as in several C18:1 and trans fatty acid isomers. None of the treatments exceeded the recommended upper limit of 4 for the n-6: n-3 ratio. Overall, energy supplementation did not affect growth performance and beef quality; however, supplementation at 1.0% of body weight improved carcass weight and backfat thickness. This strategy may increase economic returns while maintaining a favorable fatty acid profile.