Efficacy of Supplementing Lemongrass Powder on Growth, Metabolism, Immune and Endo‐Parasitic Status of Lambs in the Tropics

Background Parasitic infections are prevalent among lambs in the subtropics, adversely affecting immunity, liver health and growth performance. To efficiently combat these issues, herbs as supplements are an effective approach. Objectives The present study aims to evaluate the efficacy of lemongrass powder on growth performance, nutrient digestibility, blood biomarkers, liver enzymes, immune and endo‐parasitic status in lambs ( Ovis aries ). Methods Ten lambs (body weight [BW]: 16.67 ± 3.82 kg) were randomly assigned to two diets (5 lambs/diet) in a crossover design, consisting of two 35‐days feeding periods separated by a 14‐days washout interval. The basal diet had 14.90% crude protein and 10.57 mega joules of metabolizable energy/kg of dry matter (DM) and was considered the control diet (CL‐diet), and the lemongrass diet (LS‐diet) consisted of the basal diet + 0.50 g of lemongrass powder/kg of metabolic BW of a lamb. Feed, faeces and blood samples were collected during each feeding period. Results Lambs receiving the LS‐diet presented a better propensity of DM consumption ( p = 0.07), greater average daily gain ( p = 0.06), while showing a better feed conversion ratio ( p = 0.05) and higher growth velocity ( p = 0.02) compared to the CL‐diet. In addition, lambs given the LS‐diet improved nutrient digestibility, serum high‐density lipoprotein cholesterol and albumin, while reducing serum triglycerides, low‐density lipoprotein cholesterol and globulin compared to the CL‐diet ( p < 0.05). However, feeding the LS‐diet to lambs had no impact on serum total protein, immunoglobulin (Ig)‐M, alanine aminotransferase and gamma‐glutamyltransferase, while substantially improving serum IgG and reducing aspartate aminotransferase and alkaline phosphatase, thereby improving immunity and liver health. Lambs given the LS‐diet effectively suppressed stomach worms, Paramphistomum spp. and Eimeria spp. ( p < 0.05). Conclusions Lemongrass powder as a supplement with a basal diet had a positive impact on growth velocity, digestibility, serum cholesterol levels, liver health, immunity and endo‐parasitic status in lambs.