Virginiamycin is commonly used in livestock as a growth promoter. In the final stage of cattle farming, the dietary components of the feedlot are adjusted to produce the best quality meat. This generally involves increasing the amount of fat in the animal. In most cases, the final stage diet is grain-based, rather than grass. During this stage, additives such as virginiamycin are also introduced.
Virginiamycin is a macrolide antibiotic which has repeatedly been shown to improve animal performance. However, it is unclear whether it works by protecting the liver, or impacting the short-chain fatty acid profile in the rumen, or improving the protein flow to the small intestine.
Recently, a study at Texas A&M evaluated the effects of this additive in an attempt to understand exactly how it works. The animals were treated with 3 different dosage levels for comparison. After treatment, samples of rumen fluid, feces, and urine were collected and analyzed.
The results from this study found that virginiamycin supplementation did not effect nutrient digestibility but did increase ruminal pH and impacted the rumen dynamics. It also seemed to improve the protein flow to the small intestine.
Additional research should be done to further understand the impact of virginiamycin supplementation on the bacteria population and fermentation in the rumen. Laboratory reference standards for specific virginiamycins are available at LKT Labs:
Virginiamycin Mixture (M1 & S1)
Batista L, Rivera M, Fonseca M, et al. The influence of virginiamycin on digestion and ruminal parameters under feedlot conditions. Transl Anim Sci. 2024 Feb 14:8:txae019. PMID: 38406320