Dietary supplementation with L-carnitine and L-arginine improves testicular development and reproductive potential on aged broiler breeder roosters

This study examined the impact of L-arginine (L-Arg) and L-carnitine (LC) supplements, alone and combined, on blood parameters, lipid peroxidation, testicular histology, reproductive performance, and hormones in 50-week-old roosters. Thirty-two Arian breed broiler breeders were divided into four experimental groups in a completely randomized design. The treatments were: 1) control (CON); 2) diet with 150 mg/kg LC; 3) diet with 500 mg/kg L-Arg; and 4) diet with 75 mg/kg LC + 250 mg/kg L-Arg. The analysis of testicular tissue indicated that the malondialdehyde levels in the LC treatment group were significantly reduced compared to the other treatment groups (P ˂ 0.05). The inclusion of 150 mg/kg LC in the diet of roosters resulted in a significant increase in the diameter of the seminiferous tubules, the thickness of the seminiferous epithelium, the volume of connective tissue between the tubules, the quantity of seminiferous tubules, and the spermatogenesis index (P ˂ 0.05). Roosters fed with the L-Arg + LC mixed diet had higher concentrations of FSH and testosterone (P < 0.05). Fertility and hatchability percentages in the LC treatment were significantly higher than those in CON and L-Arg treatments (P < 0.05). Therefore, it can be concluded that L-Arg + LC prevents the severity of oxidative stress caused through modulating lipid metabolism, reducing malondialdehyde, and increasing the reproductive hormones, and improves the process of spermatogenesis and ultimately fertility and hatchability.