Abstract

Background:
Oregano essential oil, derived from Origanum vulgare and rich in bioactive compounds such as carvacrol and thymol, is a popular natural feed additive in poultry production. It acts as an alternative to growth promoters.

Aim:
This study explored the effects of Asparagus (Asparagus officinalis) (AEO) and Nettle (Urtica dioica) essential oils (NEO) on the performance, carcass traits, and blood parameters of Arian broiler chickens over a 42-day period.

Methods:
A total of 700 1-day-old chicks were randomly assigned to seven dietary treatments: a basal diet with no additives (control) and diets supplemented with 150 mg/kg protexin, 150 mg/kg avilamycin, 200 mg/kg AEO, 400 mg/kg AEO, 200 mg/kg NEO, and 400 mg/kg NEO. Each treatment group consisted of 4 replicates of 25 chicks. Body weight gain (BWG) and feed intake (FI) were monitored throughout the trial, and the feed conversion ratio (FCR) was calculated accordingly. On day 42, 8 birds were randomly selected for blood sampling to assess biochemical
parameters and carcass characteristics.

Results:
FI was significantly reduced in the groups supplemented with 400 mg/kg AEO and 400 mg/kg NEO and increased with 150 mg/kg avilamycin (p < 0.05). In contrast, BWG and FCR remained unaffected across all treatments (p > 0.05). Carcass traits, including relative weights of thighs, breast, and abdominal fat, showed no significant differences (p > 0.05). Blood parameters, including cholesterol, triglycerides, high-density lipoprotein, and lowdensity lipoprotein, also showed no significant differences among the groups (p > 0.05). However, blood glucose levels were significantly lower in the NEO treatment group at 200 and 400 mg/kg than in the control (p < 0.05). AEO exhibited moderate to good activity against gram-negative pathogenic bacteria, namely Escherichia coli (inhibition zone of 12 mm at 100% concentration, MIC 2.5%) and Salmonella enterica (inhibition zone of 10 mm at 100% concentration, MIC 1.56%), with concentration-dependent effects and predominantly bactericidal action against S. enterica (minimum bactericidal concentration/minimum inhibitory concentration ratio ≤4). In contrast, NEO exhibited weaker activity (MIC values up to 50% for E. coli). Neither essential oil in this research showed any inhibitory or bactericidal effects on beneficial gram-positive probiotic bacteria (Bifidobacterium bifidum and Lactobacillus casei).

Conclusion:
AEO and NEO have antimicrobial properties that support intestinal health and selectively promote beneficial microflora, potentially reducing pathogenic bacteria without the adverse effects of antibiotics. The study concludes that AEO and NEO can serve as viable alternatives to antibiotic growth promoters, maintaining broiler performance and health without affecting key growth and blood parameters. This aligns with growing concerns over antibiotic resistance, supporting the use of herbal supplements in poultry production. Further research is recommended to optimize the dosage.

Key words: Asparagus and nettle essential oils; Blood parameters; Broilers; Carcass traits; Performance.