Mentha piperita (peppermint) in growing Japanese quails’ diet: Serum biochemistry, meat quality, humoral immunity

• Mentha piperita improved blood lipid profile of growing quails.
• Mentha piperita increased the humoral immunity of growing quails.
• Mentha piperita improved meat quality of growing quails.

In this experiment, the effect of dietary Mentha piperita L. (MP, peppermint) on biochemical blood parameters, meat quality, and humoral immunity responses of growing Japanese quails were evaluated. A total of 360 seven-day-old quail chicks were fed six experimental diets (with 5 replicates and 12 birds each) including control positive (basal diet + antibiotic), control negative (basal diet), MPI (basal diet + 10 g/kg MP), MPII (basal diet + 20 g/kg MP), MPIII (basal diet + 30 g/kg MP), and MPIV (basal diet + 40 g/kg MP) for 5 weeks. At the end of experiment, two birds in each replicate were sacrificed for blood sampling and assessment of meat quality. The birds were injected with sheep red blood cell (SRBC, at days 18 and 28 for primary and secondary responses) and Newcastle disease virus (NDV, at day 14) antigens. Concentrations of triglycerides (TG), total cholesterol (TC), low-density lipoprotein (LDL), and alanine aminotransferase (ALT) were decreased in birds received dietary peppermint but the level of high-density lipoprotein (HDL) increased (P < 0.001) compared to control groups. Incremental levels of dietary peppermint decreased the levels of malondialdehyde (MDA), drip loss, and cooking loss in meat samples compared to control diets (P < 0.001) while humoral immunity system has been boosted in birds fed dietary peppermint (P < 0.05). Regression analysis showed that minimum rate of TC, LDL, TG, cooking loss, and MDA may be achieved with 25.7 (R2 = 0.89), 22.1 (R2 = 0.90), 21.8 (R2 = 0.64), 29.3 (R2 = 0.58), and 11.0 g/kg (R2 = 0.99) of peppermint in the diet. Moreover, the maximum rate of HDL, antibody production against secondary SRBC, and NDV antigens were obtained with 24.0 (R2 = 0.88), 13.1 (R2 = 0.99), and 26.7 g/kg (R2 = 0.98) of peppermint in the diet. Principal component analysis showed that humoral responses and HDL concentration positively correlated with peppermint groups but the use of antibiotic may impair the oxidative stability of quail meat and deteriorate the blood profile. This study revealed that peppermint at the rate of 20–30 g/kg of diet could be a promising alternative to antibiotics in order to improving blood profile, humoral immunity, and meat quality in growing Japanese quails.