Designing Next-Generation Broiler Systems with Composition or Chemotype-Guided Essential Oils: From Intestinal Ecology to Post-Harvest Meat Preservation

Essential oils from rosemary, cinnamon, and clove have attracted interest as alternatives to routine antibiotic use in poultry production. Their potential effects include improving gut health, microbial control, oxidative balance, growth performance, carcass traits, and meat preservation. However, comparing the literature is difficult because terms like “rosemary oil,” “cinnamon oil,” and “clove oil” often refer to preparations that are not chemically or functionally equivalent. These preparations vary by botanical source, chemotype, extraction method, storage, formulation, concentration, and route of exposure. This review argues that poultry outcomes should be interpreted through a chemistry- and route-based framework. Rosemary essential oil is typically rich in monoterpenes. Cinnamon oils may be cinnamaldehyde- or eugenol-dominant, depending on the species and plant organ. Clove oil is generally rich in eugenol but remains compositionally variable. These differences influence antimicrobial potency, anti-virulence activity, redox behavior, sensory impact, and stability. The review further distinguishes between direct antimicrobial injury and growth-independent virulence attenuation. It also separates dietary effects in live birds from postharvest effects on meat. Evidence suggests that dietary supplementation can influence intestinal morphology, inflammatory status, nutrient utilization, and carcass composition. These effects are especially notable when formulations are protected or encapsulated. This review aims to critically evaluate rosemary, cinnamon, and clove essential oils as non-interchangeable interventions in poultry systems. It relates their chemical identity, formulation, and route of exposure to outcomes such as gut health, microbial modulation, performance, and carcass traits.