Effects of post-feed restriction of thyme, oregano, and probiotics supplementation on growth, carcass characteristics, intestinal morphology, and ileal digestibility in broiler chickens

Document Type : Original Article

Authors

1 Associate Prof. In Ardabil Research Center of Agriculture and Natural Resources

2 Animal Science Research Department, Ardabil Agricultural and Natural Resources Research and Education Center, AREEO, Ardabil, Iran

10.30466/vrf.2026.2056009.4700
Abstract
To mitigate metabolic disorders and skeletal abnormalities associated with rapid growth in broilers, and to reduce reliance on antibiotics, strategies involving feed restriction and non-antibiotic dietary additives are increasingly explored. This study investigated the effects of various feeding methods and additives on weight gain, feed intake, feed conversion ratio (FCR), carcass characteristics, intestinal morphology, and ileal digestibility in broiler chickens. The research involved 480 one-day-old Ross 308 male broiler chickens. A 2 × 5 factorial experiment, arranged in a completely randomized design, incorporating two feeding methods (Ad libitum and quantitative restriction) and four types of additives (thyme essential oil [300 g/ton], oregano essential oil [300 g/ton], equal weight ratio of thyme and oregano essential oil [300 g/ton], and probiotic [250 g/ton], along with control diets [without additives]). Dietary supplementation with oregano essential oil significantly increased weight gain compared to the other additive groups. While the feeding method, additives, and their interactions significantly influenced feed intake in chickens, the FCR was primarily affected by the type of additive (P≤0.05). Supplementation with any of the tested additives led to reduced total feed intake and improved final FCR compared to the control group (p≤0.05). Histological analysis revealed that chickens receiving oregano exhibited the highest villus height to crypt depth ratio (p≤0.05). In conclusion, this research suggests that quantitative feed restriction, particularly when combined with specific dietary additives such as oregano essential oil, can significantly improve broiler growth performance, feed efficiency, and intestinal morphology, offering potential alternatives to conventional practices.

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Articles in Press, Accepted Manuscript
Available Online from 23 May 2026

  • Receive Date 15 March 2025
  • Revise Date 02 December 2025
  • Accept Date 07 January 2026