Effects of Dietary Supplementation with Thymol on Growth Performance, Blood Biochemistry, Rumen Fermentation...

This experiment aimed to study the effects of thymol on the growth performance, blood biochemical indices, hormone levels, rumen fermentation parameters, and rumen microbial changes of Texel-Hazak sheep ewes. Thirty healthy young hybrid ewes were selected and randomly divided into two groups, 15 each: a control group (CG) and an experimental group (EG). Under the same feeding management conditions, the diet of the CG group was not treated in any way, while the basal diet of the EG group was supplemented with 30 mg/kg of thymol. The experiment lasted 72 days, including a 12-day adaptation phase and a 60-day formal feeding period. During the formal feeding period, each ewe was offered 2 kg of diet per day on an as-fed basis. The thymol dose for the EG was calculated based on this planned daily feed allowance and was thoroughly mixed into the concentrate portion, which was completely consumed during individual feeding. The results showed that adding 30 mg/kg thymol to the diet significantly increased total weight gain and average daily gain in ewes (p < 0.01), and significantly decreased the feed-to-gain ratio (p < 0.01). It also significantly increased plasma P4 levels (p < 0.05) and significantly decreased B levels (p < 0.01). Meanwhile, the 16S rRNA sequencing results further confirmed that thymol altered ruminal microbial diversity and the relative abundance of specific bacterial taxa. These results suggest that the addition of 30 mg/kg thymol to the diet may act as a nutritional regulator, providing important insights into improving physiological status and rumen health during the growth stage of Texel-Hazak replacement ewes.