Behavioral responses of pigs to dietary alternatives to antibiotic growth promoters: a systematic review

Abstract

Intensive swine production stressors induce stress responses that compromise welfare and health, positioning behavior as a critical welfare indicator. Although antibiotics traditionally improve performance, antimicrobial resistance concerns have driven the search for alternatives. This systematic review evaluated the influence of zootechnical additives, used as alternatives to antibiotic growth promoters (AGP), on pig behavior. Following the PICO framework (pigs, antimicrobial alternatives, AGP, behavioral responses), three databases (Scopus, PubMed, Web of Science) were searched. Out of 1,893 identified articles, seven met the inclusion criteria, highlighting the scarcity of standardized behavioral research in this field. Extracted variables included biting frequency, posture (lying/standing/sitting), exploration, agonistic behavior, object interaction, reactivity, stereotypies, and vocalizations. The limited study number and heterogeneous assessment methods restricted direct comparisons between additives. While organic acids showed non-significant effects, probiotics improved exploration and activity in weaned piglets, improved human-animal relationships in sows, and reduced stress reactivity in offspring. L-glutamine increased standing time and novel object exploration in weaned piglets. Regarding phytogenics, Moringa oleifera reduced belly nosing, while Passiflora incarnata decreased aggression and biting in weaned piglets. In conclusion, feed additives can positively modulate pigs behavioral responses; however, these findings stem from limited data and require cautious interpretation. These findings highlight the potential of specific feed additives to mitigate stress-related behaviors in pigs, while emphasizing the urgent need for standardized ethological protocols to strengthen behavioral evidence across production phases.

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