Effects of Ionophores on Ruminal Function of Beef Cattle

SIMPLE SUMMARY: Ionophores are an important nutritional tool used to manipulate ruminal fermentation dynamics and improve the efficiency and performance of beef and dairy animals. Ionophores are carboxylic polyether antibiotics naturally produced by an occurring strain of Streptomyces spp. Ionophores modulate the ruminal environment by targeting and altering the metabolism of Gram-positive bacteria, resulting in an increased concentration of ruminal propionate and a reduced acetate concentration. Another pronounced effect of ionophores is the mitigation of ruminal proteolysis and the consequent reduction in ammonia synthesis. The purpose of this review is to highlight the impacts of ionophores on ruminal fermentation, leading to an improvement in the efficiency and performance of beef cattle. ABSTRACT: Ionophores have been widely used in the beef and dairy industry for decades to improve feed efficiency and performance by altering ruminal fermentation dynamics, increasing the level of propionate. Ionophores can also reduce ruminal proteolysis and ammonia synthesis, thus increasing the influx of protein into the small intestine in cattle, leading to improvements in performance and efficiency responses. Ionophores indirectly impact ruminal methanogenesis by decreasing the substrate used to produce methane. Despite the consistent benefits of using ionophores in cattle nutrition, their utilization is under public scrutiny due to concerns related to microbial adaptation. However, there is inconsistent evidence supporting these concerns, whereas ionophores are still an important dietary tool to enhance productivity and profitability in beef production systems.