Metabolism and Nutrition: Feed Additives II

A meta-analysis of the effect of Topmax (ractopamine HCl) on the performance of hen and tom turkeys when administered the last 14 d of finishing was conducted. Summary data from 18 studies were included. PROC GLIMMIX (SAS Inst.) was used with a model including fixed effects of linear and quadratic Topmax, sex, breed, age and their interactions and a random study effect. Any non-significant (α > 0.05) terms were dropped from the final model. Meta-analytical methods that weight responses by study precision of results were used. There was a significant linear relationship between level of Topmax and ADG kg/ day. For each unit change in mg/head/d (mg/hd/d) Topmax, there was a 0.002 kg/d increase in ADG. There were significant linear and quadratic relationships between level of Topmax and F:G and G:F ratios. For each unit change in mg/hd/d Topmax, there was a linear 0.065 decrease in amount of feed needed for the same amount of gain and a linear 0.009 increase in gain for the same amount of feed consumed. Both F:G and G:F ratios had a value which had a significant influence on the results. When this outlier was removed, there were no longer significant qua­ dratic relationships between level of Topmax and F:G and G:F ratios. Without the outlier, for each unit change in mg/hd/d Topmax, the linear decrease in the amount of feed needed for the same amount of gain was −0.021 and the linear increase in the gain for the same amount of feed consumed was 0.007. The results of these analyses support the conclu­ sion that feeding elevated levels of Topmax the last 14 d of finishing improves both hen and tom turkey production efficiency with expected outcomes of 0.068, 0.132 and 0.20 kg gain in toms and 0.064, 0.132, and 0.195 kg gain in hens fed 2.0, 4.0 or 6.0 mg/hd/d (respectively) relative to controls.