The effect of kefir and peppermint extract (Mentha pipperita) extract in drinking water on performance, lipid profiles, thyroid hormones and testosterone hormone of Japanese quail

Introduction: Application of antibiotics causes two major health problems, including antibiotic residues in body tissues and animal products and the resistance of pathogens to antibiotics. On the other hand, antibiotics improve growth, feed efficiency and control infectious diseases. Following the ban on the use of antibiotics as growth stimulants in the poultry industry, the EU has been paying more attention to non-antibiotic growth-promoting compounds since 2006, including organic acids, probiotics and herbs. Previous studies have shown that in many oils of dark plants Mentha pipperita, thymol, carvacrol, menthol and in some cases paracetamol are the most important components of growth improvement, their antimicrobial and antioxidant properties. kefir is also a natural probiotic. The fermenting agent of kefir milk is kefir seeds, which contain casein and the species Lactobacillus, Saccharomyces, Streptococcus and others. Diets containing Mentha pipperita, by improving the microflora of the gastrointestinal tract and reducing the population of harmful microbes, can create better conditions for the use of final feed products and thus improve the growth and better performance of chickens. In studies, the positive effects of kefir on the performance and biochemical parameters of broiler blood have been reported.Materials and Methods: This study was conducted in the animal husbandry research station of Khuzestan University of Agriculture and Natural Resources. In this study, four hundred one-day-old Japanese quails were used in a completely randomized design with four treatments, four replications and 25 observations per replication for 35 days. The experiment was performed. Treatments are: Treatment 1) Basic diet + drinking water (control group), Treatment 2) Basic diet + drinking water + 0.5% Mentha pipperita extract, Treatment 3) Basic diet + drinking water + kefir milk 2%, Treatment 4) Basic diet + drinking water + Mentha pipperita extract 0.5% + kefir milk are 2%. The weight of quails was measured at the end of each week and the feed consumed was determined. The average of daily weight gain, feed intake and feed conversion ratio were calculated. At the end of the fifth week, from each replicate, two quails with a weight close to the average were selected and slaughtered. Breast and thigh meat samples were used to measure pH, water holding capacity and meat moisture content. Also, at the end of the fifth week, two samples were randomly selected from each