Effects of garlic powder on growth, blood serum profile and caecal microbiota composition in meat-type ducks

This study investigated the effects of dietary garlic powder supplementation on growth performance, nutrient digestibility, carcase traits and caecal microbiome of meat-type ducks. A total of 288 day-old-duck (initial body weight (BW) 41 ± 2.1 g) were randomly allocated into four groups of control diet (0% garlic powder; T0) and garlic powder supplemented diets at 0.8% (T1), 1.6% (T2) and 2.4% (T3). Each group had eight replicates (pens) with nine ducks in each pen. Quadratic response (p < .001) was found on performance parameters, whereas ducks fed T1 and T2 diets had higher (p < .01) feed intake, final BW and average daily gain compared to T0 and T3 (p < .01), but FCR was unaffected. Ducks on T1 and T2 also exhibited greater carcase yield and lower non-carcase weight (p < .001), showing a quadratic pattern (p < .001). Thymus, heart, bursa of Fabricius, and ventriculus were influenced (p < .01) by garlic levels, with T2 and T3 showing increased values. Garlic powder increased (p < .001) the HDL and decreased (p < .01) the LDL content. Caecal microbiota profiling via 16S rRNA sequencing showed significant microbial diversity and community composition shifts. Alpha diversity was highest in T1, and beta diversity analysis confirmed treatment-specific clustering (PERMANOVA R2 = 0.15, p < .01). Linear discriminant analysis effect size (LEfSe) analysis identified distinct microbial biomarkers for each group, correlating with performance and digestibility traits. Functional KEGG prediction analysis revealed amino acid and vitamin metabolism in response to garlic supplementation. Overall, 0.8–1.6% garlic improved duck performance by positively altering the composition of the caecal microbiome, while excessive inclusion (2.4%) diminished these benefits.