A Meta-Analytical Approach to Evaluate the Performance of Cattle Fed Virginiamycin or Monensin Under Feedlot Conditions from Seven European Countries

This meta-analysis evaluated the growth performance of feedlot cattle fed virginiamycin (Vmax) or monensin (MON) in Europe. Twelve trials from seven European countries (Spain, Belgium, UK, Italy, Ireland, Germany, and France) conducted prior to 1999 were selected. Vmax dosage varied from 74 to 210 mg/hd/d with a median of 150 mg/hd/d and MON ranged from 150 to 210 mg/hd/d with a median of 150 mg/hd/d. Not all trials had complete data, and the analysis was conducted with the average data representing 763 animals distributed among control (CON, n=150), Vmax (n=347), and MON (n=266) treatments. The PROC GLIMMIX and PROC MIXED of SAS were used to analyze the random coefficients model in which treatment (CON, Vmax, or MON) was the only fixed effect and study was the random effect. Pen was the experimental unit and the number of animals per treatment within study was used in the WEIGHT statement. For multiple comparisons, the LSMEANS and PDIFF statements were used. Initial BW and dose were tested as covariates and removed from the statistical model if not significant (P < 0.10). The variation of ADG for CON animals was almost twice greater than for MON- and Vmax-treated animals. The ADG adjusted for study effect were 1.279, 1.336, and 1.361 kg/d for CON, MON, and Vmax, respectively (P = 0.08). Animals receiving Vmax had a greater ADG than CON animals (P = 0.03), but not different from monensin (P = 0.25). However, when adjusted for dose (P = 0.03) Vmax had significantly greater ADG (P = 0.02) than MON (1.355 vs. 1.288 kg/d; respectively) at the mean dose (123 mg/hd/d). Nonetheless, caution should be used when interpreting this result because their optimum dosage might differ. Despite a lower FCR of Vmax compared to MON (6.56 vs. 7.87, respectively), neither DMI (P = 0.93) nor FCR (P = 0.17) were different among treatments. We concluded that under European feedlot conditions, after adjusting for study effect there is evidence that Vmax might increase ADG compared to CON (1.361 vs. 1.336 kg/d, respectively; P = 0.03). Furthermore, when compared with MON at the same dose (mg/an/d), Vmax significantly increased ADG without affecting DMI or FCR.