Potential Effect of Dietary Supplementation of Tannin-Rich Forage on Mitigation of Greenhouse Gas Production, Defaunation and Rumen Function

SIMPLE SUMMARY: In tropical and subtropical regions, low availability and poor nutritional quality of forage sources, limit ruminant productivity and promote enteric production of CH(4) and CO(2) which are considered greenhouse gases (GHG). Non-conventional trees and shrubs, as forage resources, are considered an effective alternative for the improvement of animal performance as they possess good nutritional value along with their content of secondary metabolites. The aim of this experiment was to assess the effect of including Acacia mearnsii leaves in highly fibrous rations (corn stover) and its effect on rumen degradation kinetics, digestibility, microbial synthesis and in vitro production of gas, CH(4) and CO(2). It is concluded that up to 15% of A. mearnsii leaves can be recommended in the diet of ruminants as it causes a reduction in the population of protozoa (holotrich and entodiniomorph), as well as the production of CH(4), without generating adverse effects on the ruminal degradation kinetics, nutrient digestibility and microbial protein production. ABSTRACT: This experiment evaluated the effect of including Acacia mearnsii leaves in a high-fiber diet (corn stover), on ruminal degradation kinetics, digestibility, microbial biomass production, and gas, CH(4), and CO(2) production. Four experimental diets were tested, including a control with 100% corn stover (T1), and three additional diets with corn stover supplemented at 15% A. mearnsii leaves (T2), 30% A. mearnsii leaves (T3) and 45% of A. mearnsii leaves (T4). The highest dry matter in situ degradation (p ≤ 0.001) and in vitro digestibility (p ≤ 0.001) was found in T1 (80.6 and 53.4%, respectively) and T2 (76.4 and 49.6%, respectively) diets. A higher population of holotrich and entodiniomorph ruminal protozoa was found (p = 0.0001) in T1 at 12 and 24 h. Diets of T1 and T2 promoted a higher (p = 0.0001) microbial protein production (314.5 and 321.1 mg/0.5 g DM, respectively). Furthermore, a lower amount of CH(4) was found (p < 0.05) with T2, T3 and T4. It is concluded that it is possible to supplement up to 15% of A. mearnsii leaves (30.5 g TC/kg DM) in ruminant’s diets. This decreased the population of protozoa (holotrich and entodiniomorph) as well as the CH(4) production by 35.8 and 18.5%, respectively, without generating adverse effects on the ruminal degradation kinetics, nutrient digestibility and microbial protein production.