The present experiment was carried out to evaluate the effect of dietary supplementation
with betaine (BET) and thyme oil (THY) and their mixtures (MIX) on nutrients digestibility, caecum
characteristics, growth performance, carcass traits, and economic efficiency of growing rabbits. A total
number of 72 growing New Zealand white (NZW) male rabbits, 5-week-old and with average weight
616±7.82 g were divided into 9 experimental groups. The control group was fed a basal diet without
supplementation (T1), whereas the other groups were fed the same basal diet supplemented with 1500
mg BET (T2), 750 mg BET (T3), 1000 mg THY (T4), 500 mg THY (T5), 1500 mg BET + 1000 mg
THY (T6), 1500 mg BET+500 mg THY (T7), 750 mg BET + 1000 mg THY (T8), 750 mg BET + 500
mg THY (T9). The experimental period extended for 8 weeks. The results indicated that feed dry
matter digestibility and digestible energy were significantly (P<0.05) improved with rabbit fed T2, T3,
T4, T6, and T9 diets. In contrast, a significant (P<0.001) decrease in total volatile fatty acids and
ammonia-N concentration of cecum content was recorded with rabbits fed T4, T5, T7, T8 and T9 diets
compared with (T1) those fed the control diet. Feed intake, hematological parameters, and carcass
traits were not significant (P<0.05) affected by dietary supplementation. Daily weight gain was
significantly (P<0.001) increased in rabbit fed the supplemented diets except those fed T8 diet. Feed
conversion ratio and economic efficiency recorded the best results with rabbits fed T2, T4 and T6
diets. Dietary supplementation with 1500 mg betaine or 1000 mg thyme oil/kg diet or mixture of
theme with the same levels are recommended to improve the feed utilization and growth performance
parameters and health status of NZW rabbits.