ABSTRACT Replacing antibiotic growth promoters with effective alternatives has attracted increasing attention in modern swine production. Phytochemicals are promising candidates, but their evaluation has largely been limited to short‐term trials or specific production phases. Here, we conducted a longitudinal trial in which piglets were assigned to four groups: negative control (NC), positive control with antibiotics and high dietary zinc (PC), and two phytochemical‐supplemented diets containing Lippia origanoides and Rosmarinus officinalis extracts (Phyt1 and Phyt2). Growth performance was monitored throughout the nursery (d 0–42), growing (d 42–98), and finishing (d 98–155) phases. PC pigs showed higher body weight and average daily gain (ADG) during the nursery phase, but these benefits disappeared after antibiotic and zinc withdrawal. In contrast, Phyt1 and Phyt2 pigs exhibited improved ADG and feed efficiency during the finishing phase, indicating a more sustained growth response. Microbiota profiling revealed reduced diversity and an increased enrichment of potential pathogens (e.g., Clostridium sensu stricto 1 and Terrisporobacter ) in the PC group, whereas phytochemical supplementation preserved microbial diversity and promoted beneficial taxa such as Lactobacillus amylovorus . Functional prediction showed early (d 16) downregulation of teichoic acid biosynthesis and cationic antimicrobial peptide resistance pathways in both PC and Phyt2 groups. By d 155, Phyt2 pigs exhibited enrichment in amino acid and carbohydrate metabolism pathways, which may support their superior late‐stage growth. Overall, these findings demonstrate that phytochemicals, particularly Phyt2, can serve as potential antibiotic alternatives by supporting gut health, modulating microbial functions, and promoting sustained growth performance in a longitudinal manner across multiple production phases.
Liu et al. (Fri,) studied this question.