Growth promoters have been widely used as a strategy to improve productivity, and great benefits have been observed throughout the meat production chain. However, the prohibition of growth promoters in several countries, as well as consumer rejection, has led industry and the academy to search for alternatives. For decades, the inclusion of phytochemicals in animal feed has been proposed as a replacement for traditional growth promoters. However, there are many concerns about the application of phytochemicals and their impact on the various links in the meat production chain (productive performance, carcass and meat quality). Therefore, the effects of these feed additives are reviewed in this article, along with their potential safety and consumer benefits, to understand the current state of their use. In summary, the replacement of traditional growth promoters in experiments with broilers yielded benefits in all aspects of the meat production chain, such as improvements in productive performance and carcass and meat quality. Although the effects in pigs have been similar to those observed in broilers, fewer studies have been carried out in pigs, and there is a need to define the types of phytochemicals to be used and the appropriate stages for adding such compounds. In regard to ruminant diets, few studies have been conducted, and their results have been inconclusive. Therefore, it is necessary to propose more in vivo studies to determine other strategies for phytochemical inclusion in the production phases and to select the appropriate types of compounds. It is also necessary to define the variables that will best elucidate the mechanism(s) of action that will enable the future replacement of synthetic growth promoters with phytochemical feed additives.

FA dietary supplementation on the growth performance, carcass traits and histochemical characteristics of the Longissimus thoracis muscle from finishing pigs was investigated. Four hundred and twenty pigs were used in this study, and 105 animals (with five replicate pens and 21 pigs per pen) were assigned to one of four treatments: basal diet (BD) without additives (C−); BD + 10 ppm ractopamine hydrochloride + 0.97% lysine (C+); BD + 25 ppm of FA (FA); and BD + 25 ppm of FA + 0.97% lysine (FA-Lys). Dietary supplementation with FA or ractopamine increased both the average daily gain (14%) and loin muscle area (19%), while fat deposition decreased by 53%, in comparison with C− (p < 0.05). The growth performance of pigs treated with FA was similar to those of ractopamine (p > 0.05). The histochemical analysis showed that FA and C+ treatments induced a shift in muscle fiber types: from fast fibers to intermediate (alkaline ATPase) and from oxidative to glycolytic fibers. Muscle tissues from animals treated with FA or ractopamine had a lower cross-sectional area and a greater number of muscle fibers per area (p < 0.05). Findings regarding growth performance and carcass traits indicate that FA supplementation at 25 ppm without extra-lysine can replace the use of ractopamine as a growth promoter in finishing pigs.