Exploring Interactions Between Pre-Grazing Sward Height and Energy Supplementation on Beef Cattle Responses

This study evaluated the interaction between energy supplementation and pre-grazing sward height on grazing behavior, nutrient intake, digestion, and nitrogen metabolism of cattle. Eight rumen-cannulated Nellore steers (24 mo; 343 ± 7.4 kg BW) grazed palisade grass (Urochloa brizantha cv. Marandu) managed at 25 or 35 cm pre-grazing height until a 15 cm post-grazing target. Treatments were arranged in a 2 × 2 factorial structure: two sward heights and two supplementation levels (mineral supplement only or ground corn at 0.6% BW, DM basis). The experiment was conducted as two replicated 4 × 4 Latin squares, with eight animals, four treatments, and four experimental periods. An interaction (p = 0.02) showed that supplementation reduced grazing time only at 35 cm. Steers grazing 25 cm swards spent less time grazing, rested more, took fewer steps, had higher bite rates, and consumed more forage (p < 0.05). Supplementation reduced forage intake but increased total DM intake, improved forage NDF and total DM digestibility, increased microbial protein synthesis, enhanced nitrogen retention, reduced ruminal ammonia-N, urinary N losses, and the acetate:propionate ratio (p ≤ 0.05). Steers grazing 25 cm swards also exhibited greater ruminal ammonia-N, urinary N excretion, and nitrogen retention. Managing pastures at 25 cm improved forage harvesting efficiency, while energy supplementation enhanced rumen fermentation, nitrogen utilization, and overall grazing efficiency, with potential environmental benefits.