Arginine Promotes Testicular Development in Boars through Nitric Oxide and Putrescine

Abstract Background: The present work aimed to explore the influence of arginine on testicular development in boars and the underlying mechanism. Methods: To this end, thirty 30-day-old male Duroc piglets (7.00 ± 0.30 kg) were randomly sorted into two groups maintained on either a basal diet (CON, n = 15) or a diet supplemented with 0.8% arginine (ARG, n = 15). The average daily gain, average daily feed intake, and testicular volume were determined periodically, and serum samples were collected once every 30 days. The amino acid composition and arginine metabolite levels were estimated in testes samples, collected by castration of three 150-day-old boars randomly selected from each group. Boars semen was collected at 240 days of age to estimate sperm production and quality. Results: The results showed that dietary supplementation of arginine had no effect on boar growth performance (P > 0.05) but increased the testicular volume and weight of 120- and 150-day-old boars, respectively (P < 0.05). Quantitative analysis of testicular histology showed a higher value for the number of spermatogonia and height of the seminiferous epithelium in the ARG group (P < 0.05). The sperm density, total number of sperm, and effective number of sperm of the boars in the ARG group increased significantly compared with the CON group (P < 0.05). Although arginine supplementation did not affect plasma amino acid levels, the testicular arginine levels in 150-day-old boars showed a significant increase (P < 0.05). The level of serum nitric oxide (NO) and activity of nitric oxide synthase (NOS) also increased in 150-day-old boars in the ARG group (P < 0.05). Interestingly, dietary supplementation of arginine increased the testicular levels of putrescine in 150-day-old boars (P < 0.05). Conclusions: These results indicate that arginine supplementation increases serum NO levels and testicular arginine and putrescine levels, thereby improving testicular development and semen quality in boars.