Dietary valine affects Japanese quails' sperm parameters and testis histology

Valine is an essential amino acid that participates in various physiological and metabolic activities. The objective of the present study was to investigate the influence of different valine levels in the diet on the reproductive performance of adult male Japanese quails. Forty male quail chicks (14-24 week old) were employed in a completely randomized design with 5 treatments (0.65, 0.75, 0.85, 0.95, and 1.05 % valine in the diet), 4 replicates and 2 birds in each replicate over a period of 35 days following a 14-day adaptation period. Semen was collected weekly, and its characteristics were analyzed. The birds were then ethically slaughtered, and histological analyses were performed on testicular samples. Results showed that the different valine levels had no significant effect on testicle volume, length and relative weight, although testicle diameter tended to decrease with increasing valine level in the diet in a linear and quadratic manner (p < 0.05). The total motility and progressive motility of sperm decreased with an increase in dietary valine (p < 0.05). Abnormal sperm morphology increased with increasing valine level in the diet and the difference between treatments was significant. Different valine levels in the diet significantly affected the height of seminiferous tubule epithelia, diameter and number of tubules as well as the tubular differentiation index of the testis; but the spermatogenic index was not affected by the treatments. The findings of the study indicate that when valine levels in the diet exceed 0.75 %, there is an adverse impact on testicular volume and diameter, as well as the qualitative properties of sperm in adult quails. It is advisable to pursue additional research in this area.