Fortification of tropical macroalgae (Gelidium sp., Gracilaria sp., Sargassum sp., Ulva sp.) enhances mineral profile, strength, and ruminal degradability of mineral blocks for beef cattle

Objectives: Mineral blocks are widely used for ruminant supplementation, but their low mineral availability and weak physical properties often limit nutrient utilization. This study evaluated the effects of fortifying mineral blocks with tropical macroalgae on their mineral composition, physical quality, ruminal degradability, and palatability in Ongole crossbred bulls. Materials and Methods: The study employed a completely randomized design (CRD) with five treatments, comprising one non-fortified control (MBNF) and four macroalgae-fortified mineral blocks (MBFM) containing Gelidium sp., Gracilaria sp., Sargassum sp., or Ulva sp., each replicated three times. The mineral composition was determined by X-ray fluorescence (XRF), and the physical properties were evaluated in accordance with the Indonesian National Standard (SNI 1974:2011). In vitro ruminal degradation and gas production were measured over a 72-h incubation in five replicates per treatment, whereas palatability was assessed in 10 Ongole crossbred bulls. Data were analyzed using analysis of variance (ANOVA), and mean differences were tested by Duncan’s Multiple Range Test at p < 0.05. Results: Fortification with Gelidium sp. significantly increased Potassium (K), Iron (Fe), Manganese (Mn), and Copper (Cu) contents compared with MBNF (p < 0.05). Compressive strength improved by up to 69%, particularly in Gelidium-fortified blocks (p < 0.05). Ruminal degradability was enhanced, with dry matter digestibility and organic matter digestibility increasing by 39% and 36%, respectively (p < 0.05). Palatability tests showed no significant differences in block consumption between MBFM and MBNF (p > 0.05). Conclusions: Fortifying mineral blocks with Gelidium sp. improved mineral enrichment, compressive strength, and ruminal degradability without reducing palatability, indicating its potential as an effective mineral supplementation strategy for Ongole crossbred bulls.