Background and Aim: Secondary bioactive compounds of medicinal plants exert anti-inflammatory, antimicrobial, antioxidant, and metabolism-modulating effects. This study aimed to investigate the effect of feeding 4-hexylresorcinol, as well as its combinations with gamma-octalactone and 7-hydroxycoumarin, on the digestibility of dietary nutrients, weight gain, and quality characteristics of the meat and liver of Arbor Acres broiler chickens.

Materials and Methods: The following feeding scheme was applied on the chickens: Control, basal diet (BD); I experimental, BD + 4-hexylresorcinol at 0.5 mg/kg of live weight per day; II experimental, BD + 4-hexylresorcinol + gamma-octalactone at 0.4 mg/kg of live weight per day; III experimental, BD + 4-hexylresorcinol + 7-hydroxycoumarin at 0.1 and 0.15 mg/kg of live weight per day; and IV experimental, BD + 4-hexylresorcinol + gamma-octalactone + 7-hydroxycoumarin at 0.05, 0.15, and 0.01 mg/kg of live weight per day.

Results: Chickens in I, II, and IV experimental groups at the age of 35 days showed superior live weight than chickens in the control group. Supplementation with all the tested additives, except the combination 4-hexylresorcinol + 7-hydroxycoumarin, significantly increased the digestibility coefficients of dietary nutrients. Supplementation with the combinations 4-hexylresorcinol + gamma-octalactone and 4-hexylresorcinol + gamma-octalactone + 7-hydroxycoumarin significantly increased the amount of fat in the pectoral muscles. However, the mass fraction of fat in the thigh muscles of broiler chickens decreased in II, III, and IV experimental groups. The pectoral muscles of broiler chickens in experimental Group IV contained small amounts of lysine, tyrosine, histidine, leucine–isoleucine, methionine, valine, proline, threonine, serine, alanine, and glycine. Supplementation with pure 4-hexylresorcinol significantly reduced the levels of lysine, phenylalanine, histidine, leucine–isoleucine, methionine, valine, proline, threonine, and alanine in the thigh muscles. However, supplementation with pure 4-hexylresorcinol significantly increased the concentrations of P, Fe, Se, Zn, and B and decreased the concentrations of I, Ni, V, Al, and Pb in the pectoral muscles. Supplementation with the combination 4-hexylresorcinol + gamma-octalactone + 7-hydroxycoumarin resulted in the accumulation of Ca, Co, Fe, Mn, Se, Zn, and Li and a decrease in the concentrations of K, Mg, and V.

Conclusion: Supplementation with all the tested additives, except the combination 4-hexylresorcinol + 7-hydroxycoumarin, exerted a positive effect on the indicators of live weight gain and dietary nutrient digestibility in broiler chickens. Supplementation with the combinations 4-hexylresorcinol + gamma-octalactone and 4-hexylresorcinol + gamma-octalactone + 7-hydroxycoumarin increased the amount of fat in the pectoral muscles but decreased it in the thigh muscles. Supplementation with all the tested additives decreased the concentrations of I in the pectoral muscles and Zn in the thigh muscles in all the experimental groups compared with those in the control group.

Keywords: chickens, liver, medicinal plants, pectoral muscles.