Abstract
Simple SummaryIonophores 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.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.
Highlights
Feed additives are an important dietary tool to enhance efficiency and profitability in grazing and feedlot cattle systems [1,2]
Ionophores are carboxylic polyether antibiotics naturally produced by an occurring strain of Streptomyces spp and provided to beef cattle orally [9,10]
Schären et al [4] reported no alteration in the abundance of methanogenic bacteria in the presence of monensin, indicating that the shift of the acetate:propionate ratio caused by ionophores reduces the substrate available to methanogenic bacteria (Figure 1), and decreases methane production
Summary
Feed additives are an important dietary tool to enhance efficiency and profitability in grazing and feedlot cattle systems [1,2]. Dietary ionophores can provide the ruminal dynamics with a more efficient fermentation route by altering the ruminal microbiome environment and reducing the substrate for methanogenic bacteria [1,2,4,14,15]. Another noticeable effect of dietary ionophores is mitigating ruminal proteolysis and subsequent reduction in ammonia synthesis [14,16,17]. The purpose of this review is to provide an overview of the impacts of ionophores on ruminal fermentation of beef cattle
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