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 CH4 and CO2 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, CH4 and CO2. 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 CH4, without generating adverse effects on the ruminal degradation kinetics, nutrient digestibility and microbial protein production. 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, CH4, and CO2 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 CH4 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 CH4 production by 35.8 and 18.5%, respectively, without generating adverse effects on the ruminal degradation kinetics, nutrient digestibility and microbial protein production.

Automated summary

The inclusion of Acacia mearnsii leaves in ruminant's diets has been found to reduce the population of protozoa and methane production while not affecting ruminal degradation kinetics, nutrient digestibility, and microbial protein production. Up to 15% of A. mearnsii leaves can be recommended as a supplement in high-fiber diets without adverse effects.