Evaluating the Effect of Quebracho Tannin Supplementation Upon Ruminant Production

Ruminant production is essential to meeting the high-quality protein requirements of an increasing global population. However, gaseous byproducts from ruminant production such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) can reduce energy efficiency and be detrimental to the environment. Increased societal awareness of food safety and environmental stewardship has driven the search for natural feed additives that can assist in mitigating greenhouse gases from animal agriculture. Condensed tannins are a diverse group of naturally occurring secondary metabolites that are potential alternative feed additives within ruminant nutrition due to improved protein efficiency and CH4 mitigation. We investigated how quebracho tannin (QT) extract inclusion at differing rates, 0, 1.5, 3, and 4.5% DM, affected digestibility parameters, enteric gas production, energetic efficiency, nitrogen retention, and fecal gas flux in beef steers. The inclusion of QT above 1.5% decreased the digestibility of DM, organic matter, and nitrogen (P < 0.01) with variable responses for fiber digestibility across trials. Addition of QT altered excretion profiles with fecal N-to-total N excreted ratio and fecal N-to-urinary N ratio increasing with inclusion of QT, however, N retention was not different. Animals receiving QT had increased fecal energy (P < 0.001), resulting in decreased digestible energy (P < 0.01). Metabolizable energy was not different across treatments with all inclusion levels maintaining a metabolizable energy-to-digestible energy ratio of 0.86 –– 0.87. Heat energy decreased (P= 0.01) with increased QT inclusion rate, but there was no difference in retained energy. For fecal gas flux trials, season and animal greatly impacted emissions, resulting in large variation between trials. The daily flux of CO2 was influenced by soil moisture and temperature (r = 0.34; P < 0.01), whereas CH4 and N2O were associated with soil moisture. Large variation in animal response to QT resulted in discrepancies among trials. However, within certain environments QT supplementation could potentially improve animal performance and reduce fecal gas emissions. Future studies that encompass greater animal variability are required to determine the feasibility of QT utilization