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Abstract
Feed additives include numerous classes of compounds that when fed to finishing beef cattle can alter rumen metabolism, prevent pathogen infections, and improve performance. Essential oils, monensin, tylosin, and ractopamine are feed additives with differing modes of action and performance responses dependent on numerous dietary and animal factors.
A cattle finishing experiment and metabolism experiment were conducted to evaluate the performance and carcass response to specific essential oil mixtures (EOM) and explain the mechanistic mode of action of EOM. Compared to control, improved G:F was observed when EOM were fed in combination with tylosin and this response was equivocal to a diet supplemented with monensin and tylosin. Additionally, metabolism characteristics indicated greater acetate volatile fatty acid (VFA) concentration with a similar acetate:propionate ratio with EOM when compared to monensin.
To determine the effectiveness of monensin and ractopamine in diets containing modified distillers grains plus solubles (MDGS), an individual steer trial was conducted. In a forage diet, monensin and MDGS were effective at improving steer performance or rumen fermentation characteristics. Ractopamine supplementation during a finisher phase increased performance with concomitant improvement in HCW. Addition of MDGS improved rumen fermentation characteristics with performance response improved slightly. Minimal rumen fermentation differences were observed when diets were supplemented with monensin or ractopamine.
Three feeding trials with different corn processing methods were conducted to determine effectiveness of monensin and tylosin in diets containing wet distillers grains plus solubles (WDGS). An interaction between corn processing and WDGS was observed for performance with WDGS having a greater feeding value in diets containing dry-rolled and high-moisture corn compared to steam-flaked corn. Inclusion of monensin and tylosin in WDGS diets improved G:F and decreased liver abscesses compared to a WDGS diet without these feed additives regardless of corn processing method utilized.
