282 Awardee Talk: Effects of Various Feed Additives on Finishing Pig Feed Efficiency: A Review
Authors: Rao Zhong-Xing , Tokach Mike D , Woodworth Jason C , DeRouchey Joel M , Goodband Robert D , Gebhardt Jordan T 
Published: October 2023

Abstract
Several feed additives have shown benefits throughout the literature in improving growth performance and carcass characteristics when fed to finishing pigs. The mechanisms of action of these feed additives may be by improving health status, energy metabolism, and/or nutrient digestibility. However, the results have been variable and have not been well summarized. In addition, few of the feed additives have a review of all the available literature, and to our knowledge, no review summarizes each feed additive in one centralized effort. Therefore, this review summarizes the available research on feed additives fed in swine diets for the grow-finish phase (Table 1). The feed additive categories chosen for this review were acidifiers, betaine, Cr, conjugated linoleic acid (CLA), Cu, direct-fed microbials (DFM), carbohydrases, proteases, phytases, multi-enzymes, essential oils (EO), L-carnitine, yeasts, and Zn. Research articles were collected from online research databases. Inclusion and exclusion criteria were utilized to select qualified research articles. The percentage difference for each response variable between the treatment and control group was calculated to determine the magnitude of effect. Results indicated that positive outcomes for each feed additive can be found; however, the magnitude of improvement varied, and many experiments did not observe statistically significant improvements in response criteria. For G:F, acidifiers (n = 65 total comparisons, 3.1% improvement across all comparisons), betaine (n = 35, 2.7%), CLA (n = 57, 3.5%), multi-enzymes (n = 29, 3.3%), DFM (n = 66, 3.3%), L-carnitine (n = 24, 2.5%), and yeasts (n = 33, 2.7%) showed relatively large and positive effects (&gt; 2%) across a reasonable number of comparisons (n &gt; 20) with &gt; 14% of them being statistically ( P≤ 0.10) positive. For ADG, DFM (n = 71, 3.3%), Cu (n = 155, 2.5%), L-carnitine (n = 24, 2.1%), and multi-enzymes (n = 29, 3.1%) showed relatively large and positive effects (&gt;2%) across a reasonable number of comparisons (n &gt;20) with &gt; 21% of them being statistically (P ≤ 0.10) positive. Moreover, except for betaine, Cr, CLA, and L-carnitine, most feed additives showed little, inconsistent, or non-significant effects on carcass characteristics. The improvements in carcass characteristics were probably due to the improved energy metabolism. Publication bias and the location of studies need to be considered when evaluating the data, as many studies that show no effect might not be published. Furthermore, even though the economics was not discussed in this review, the decision to include feed additives in the pig diets should consider the return on investment based on the price and the magnitude of benefit. In conclusion, this literature review provides descriptive analysis and databases for commonly used feed additives in the hope of better understanding the effect of feed additives on improving the efficiency of swine production.