Effects of 3-nitrooxypropanol on productivity and carcass traits in feedlot cattle fed a steam-flaked wheat diet in a commercial setting

Context As the livestock sector faces mounting expectations to curb greenhouse gas emissions alongside evolving public attitudes toward feed additives, rigorous evaluation of emission-mitigation additives within commercial feedlot operations is warranted. Aims The present study evaluated the impact of 3-nitrooxypropanol (3-NOP) supplementation on growth performance and carcass outcomes of feedlot cattle fed a steam-flaked wheat diet in a large-scale commercial setting. Methods In total, 9492 crossbred steers and heifers (bodyweight 362.8 ± 30.4 kg, mean ± s.d. ) were randomly assigned to one of two treatments, namely, control (no 3-NOP) or 3-NOP (100 mg/kg DM dose of 3-NOP). Cattle were transitioned to a finisher ration over 11 days and then fed for 95 days, during which each treatment remained on its respective diet for the 106 day finishing period. All statistical procedures were performed using SAS software, where the pen was considered the experimental unit and block as random. Key results The 3-NOP cattle had significantly lower dry-matter intake than did the control (8.78 vs 8.91 kg/day respectively). Moreover, average daily gain, feed:gain, morbidity, carcass weight, and dressing percentage were unaffected. The 3-NOP cattle had a reduced P8 fat depth and Meat Standards Australia (MSA) marbling score, and tended to have lower Ausmeat marbling scores; however, these differences were practically small, and overall MSA index was not affected. Conclusion The study indicated that 3-NOP can be confidently supplemented to feedlot cattle finished on steam-flaked wheat diets without negatively influencing key feedlot performance and carcass characteristics. Implications Feeding 3-NOP to finishing cattle reduced dry-matter intake, resulting in diminished marbling and fat depth, without negatively influencing cattle performance or health.