329 Effectiveness of Virginiamycin Administration on Animal Health and the Observed Impacts on Growth, Development, and Intake Dynamics in Growing and Finishing Calves

Abstract

Abstract Virginiamycin (VM) is an antibiotic that possesses antimicrobial properties due to its ability to block protein synthase in Gram-positive bacteria. It reduces lactic acidosis and the incidence of liver abscesses. Animal growth and development is brought about because of improved ruminal health, and animal health and welfare. This study evaluated the continuous or intermittent provision of VM during the growing and finishing phases on 120 Angus-crossbred steers (291 ± 28 kg) in 20 pens equipped with a Calan gate feed system from which animals received VM (240 mg/d) as follow: no VM (T000); VM in the last 50 d (T001); VM for the last 100 d (T011); VM in the first 50 d (T100); VM in the first 100 d (T110); and VM for 150 d (T111). Data were analyzed using a random coefficients model with the pen as a random effect and animals within treatment as the subject. The T011 tended (0.075 ≥ P ≥ 0.052) to have a greater carcass, final shrunk body weight compared with T110. Empty body fat (EBF; %) tended (0.080 ≤ P ≤ 0.050) to be less for animals that consumed VM regardless of the period or length of feeding. Dry matter intake (DMI) was lesser for T111 compared with T000, and greater for T011 compared with T110 (P ≤ 0.028), which resulted in greater average daily gain (ADG) with no difference in feed efficiency (P = 0.015 and 0.225, respectively). ADG-adjusted metabolizable energy (aME) content increased by 3.08% for T111 compared with T000. This study indicated that daily supplementation of 240 mg VM during the whole feeding phase increased feed efficiency and paME, whereas when withdrawn during the end of the finishing phase (T110) can impair DMI and ADG.