Effects of Thymus vulgaris, Euphorbia hirta, and Allium sativum as phytogenic feed additives on nutrient digestibility, gut microbiota, and performance of Kabir chickens in Cameroon

This study evaluated the effects of Thymus vulgaris (thyme), Euphorbia hirta, and Allium sativum (garlic) as phytogenic feed additives on feed digestibility, gut microbiota, growth performance, and survival of Cameroon Kabir chicken roosters. One hundred and sixty 8-week-old Kabir roosters were randomly allocated to eight treatments in a completely randomized design with two replicates of 10 birds each. The treatments consisted of basal diets supplemented with 0.75% and 1.5% E. hirta, 0.5% and 1.0% T. vulgaris, 0.5% and 1.0% A. sativum, a positive control (oxytetracycline 0.5 g/L in drinking water), and a negative control (basal diet only). The experiment lasted 16 weeks following a 2-week acclimatization period. Although supplementation had no significant effects (P > 0.05) on feed intake, average daily weight gain, feed conversion ratio, or survival rates, the study had limited statistical power (0.59) to detect differences in these growth parameters. Notable improvements were observed in nutrient digestibility and gut microbiota. E. hirta at 0.75% significantly improved carbohydrate digestibility (86.6%), while several plant treatments significantly affected ash and cellulose digestibility (P < 0.05). All three phytogenic additives markedly reduced total bacterial counts in the caecum compared to both controls (P < 0.001), with E. hirta at 1.5% showing the strongest effect. The plant additives generally outperformed oxytetracycline in modulating gut microbiota. These findings indicate that Thymus vulgaris, Euphorbia hirta, and Allium sativum can serve as effective natural alternatives to antibiotic growth promoters, particularly for improving nutrient utilization and controlling pathogenic gut bacteria in Kabir chickens. They offer a promising, locally available option for sustainable poultry production in Cameroon.