Effects of Calcareous Marine Algae on Feedlot Performance, Carcass Traits, Nutrient Digestion and Enteric Methane Emissions of Feedlot-Finished Nellore Heifers

Global population growth has intensified the demand for productive and sustainable livestock systems. Lithothamnium calcareum, a calcareous marine alga, has been investigated as a natural feed additive for cattle diets. This study evaluated the effects of L. calcareum supplementation on performance, carcass traits, nutrient digestibility, nitrogen metabolism, urinary and fecal pH, and enteric methane emissions in Nellore heifers during the finishing phase. Thirty-six heifers (BW = 268.8 ± 7.3 kg) were assigned to individual pens in a completely randomized design and fed ad libitum diets (25:75 forage-to-concentrate ratio, DM basis). Treatments were: (1) sodium bicarbonate (110 g/heifer/day) and (2) L. calcareum (60 g/heifer/day). The 96-day trial included 12 days of adaptation and 84 days on the finishing diet. Methane emissions were measured using the sulfur hexafluoride (SF6) tracer technique. L. calcareum did not affect performance, carcass traits, nitrogen metabolism, or apparent total tract digestibility (all p ≥ 0.106), but reduced urine pH (p ≤ 0.001) and tended to lower methane emissions (−8.2%; p = 0.079). Thus, L. calcareum appears to be a viable natural alternative to sodium bicarbonate in finishing diets for Nellore heifers, maintaining productive performance and potentially reducing enteric methane output.