The Effect of Vitamin A Administration on Testicular Development in Peri-Pubertal Bulls

The establishment of the final number of Sertoli cells in the calf testicle determines daily sperm production in the bull. Retinoic Acid (RA) has been described as one of many factors having an effect on Sertoli cell proliferation. Fourteen Angus and Shorthorn bulls (287 ± 3.3 days of age, 310 ± 10 Kg) were assigned randomly to one of two treatments: 1) Intramuscular injection of 1 million IU vitamin A (Vit A) or 2) no treatment (Control). Scrotal circumference (SC) was measured in all bulls at the time of the treatment application and 11 days later at castration. Weight of the testes and epididymis were obtained, and samples of parenchyma were collected from each testicle. Samples were fixed in formaldehyde, embedded in paraffin and cut into 5 µm sections. Slides were deparaffinized with successive washes of xylene and alcohol. After antigen retrieval and blocking with 10 percent normal goat serum, sections were incubated sequentially with mouse monoclonal anti-androgen receptor antibody (AR441), ab9474 (abcam, Cambridge, MA) and CF633 Goat Anti-Rabbit IgG (H+L) fluorescent stain (Biotium, Fremont, CA). Samples were examined under a fluorescent microscope and the images captured with a digital camera and processed using Image-Pro Plus software. Effects of Vit A treatment on SC, testicular weight, testicular parenchyma weight and epididymis weight, number of Sertoli cells, germ cell, and ratio of germ cells to Sertoli cells within the seminiferous tubule (ST) were analyzed using the ANOVA procedure of SAS. No differences were observed among treatments for SC (1.63 ± 0.26 vs. 2.17 ± 0.17 cm; P = 0.135), testicular weight (228.17 ± 17.00 vs. 221.79±24.98g ;P=0.575), testicular parenchyma weight (141.02±11.82 vs. 131.46±14.49 g; P=0.615), epididymis weight (12.01±1.10 vs. 9.43±1.01 g; P=0.109), number of Sertoli cells/Seminiferous Tubule (ST) (45.56 ± 3.14 vs. 48.04 ± 2.18; P=0.557), number of germ cells/ST (217.29 ± 26.83 vs. 156.04 ± 16.75; P=0.100) and the Germ to Sertoli cell ratio (5.03 ± 0.93 vs. 3.30 ± 0.43; P=0.158) for vitamin A and control, respectively. Within the confines of the current experiment, vitamin A has no effect on fertility when administered in peri-pubertal bulls.