"Effect of Supplementing Diets with Different Levels of Thyme (Thymus vulgaris) Powder on Growth Performance, Digestive Physiology, Carcass Traits, and Fat Distribution Pattern in Barbary Lambs under Semi-Arid Conditions"

Abstract

This study aimed to evaluate the physiological and anatomical effects of dietary supplementation with different levels of thyme powder (Thymus vulgaris) as a natural phytogenic growth promoter alternative to antibiotics in growing local Barbary lambs under the semi-arid environmental conditions of Bani Walid. Twenty-four male fat-tailed Barbary lambs  with an average initial body weight of 24.5 ± 0.32 kg/lamb were randomly assigned to three equal groups (8 lambs/treatment) for a 90-day trial. The experimental groups consisted of the Control group (basal diet without additives) Treatment 1 (T1: supplemented with 1.5% thyme powder of the concentrate feed)  and Treatment 2 (T2: supplemented with 3.0% thyme powder of the concentrate feed).

The results showed that thyme powder supplementation induced a linear and significant (P < 0.05) improvement in the average daily gain (ADG) The ADG increased from 149g/day in the Control group to 168g/day in T1  and peaked at 185 g/day in T2  leading to a remarkable physiological enhancement in the feed conversion ratio (FCR) without any significant effect on daily dry matter intake.

Anatomically, thyme-supplemented groups exhibited significant increases in carcass weights, dressing percentage and Longissimus dorsi (rib-eye) area. Furthermore the study clearly established a "Smart Fat Partitioning" mechanism dietary thyme caused a sharp linear reduction (P < 0.001) in total internal visceral fat (dropping from 1.03 kg in the Control to 0.78 kg in T2) while simultaneously channeling metabolic energy towards increasing the external fat-tail weight.

Blood biochemical profiling confirmed safe liver and kidney functions alongside a significant decrease in serum urea total cholesterol and triglycerides. Moreover the bioactive phenolic compounds in thyme enhanced humoral immunity (elevated globulin) and improved systemic blood antioxidant status by increasing superoxide dismutase (SOD) activity and inducing a sharp continuous decline in malondialdehyde (MDA) levels.

In conclusion incorporating dietary thyme powder up to 3% serves as a highly effective and safe phytogenic strategy to optimize growth performance enhance the anatomical and health value of the carcass and upgrade the metabolic efficiency of local fattening lambs.