Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2003
Publication Date: 10/27/2003
Citation: Jimenez-Severiano, H., Fitzpatrick, L.A., D'Occhio, M.J., Ford, J.J., Mussard, M.L., Kinder, J.E., Lunstra, D.D. 2003. Testis development in bulls treated with a GnRH agonist [abstract]. Proceedings of the 39th Annual Meeting of Research in Animal Production, October 27-31, 2003, Mexico, DF. Mexico. p. 160. Interpretive Summary:
Technical Abstract: In cattle, neopubertal chronic treatment with GnRH agonists increases steroidogenic and spermatogenic capacities, perhaps by obviating LH pulsatility. It has been suggested that this treatment might reduce age at puberty in less precocious genotypes such as Zebu (Bos indicus). The objective was to compare testis characteristics of 7/8 B. indicus 1/8 B. taurus bulls treated with the GnRH agonist, deslorelin, at different times and duration during their development. An additional objective was to determine the usefulness of a stain for the transcription factor GATA-4 as a specific marker for Sertoli cell nuclei. Bulls (54) were allocated to nine groups (n=6), and received s.c. deslorelin implants, as follows: G1, from birth to 3 mo of age; G2, from 3 to 6 mo; G3, from 6 to 9 mo; G4, from 9 to 12 mo; G5, from birth to 15 mo; G6, from 3 to 15 mo; G7, from 6 to 15 mo; G8, from 12 to 15 mo; and G9, control (no implant). Bulls were castrated at 19 mo of age. Paraffin sections (10 um) were subjected to quantitative morphometry and GATA-4 immunohistochemistry. Data were analyzed by GLM and mixed models of SAS. Dunnett's test was used to compare each treated group with G9. At castration, all G9 bulls (6/6) had attained puberty, while a lower proportion (P<0.05) had reached puberty in G2 (2/5) and G6 (1/6). Bulls in G2 and G6 also had lower (P<0.05) testis weight, compared with G9 (217±45, 181±41 and 404±41 g, respectively). Total volume of seminiferous epithelium (109±26, 96±24 and 209±24 cm3, respectively) and total daily sperm production (3.8±1.2, 3.4±1.1 and 8.2±1.1 x 1,000,000,000, respectively) in G2 and G6 were only half of that observed in G9. Spermatids were observed in less than 50% of seminiferous tubules in G2, G6 and G7, compared with 82% in G9 (P<0.05). Staining for GATA-4 was specific for and abundantly expressed in the Sertoli cell nucleus in both pre- and post-pubertal bulls, and no other cell nucleus inside the seminiferous tubule was positive for GATA-4. Total numbers of Sertoli cells and Sertoli cell nuclear volume were not affected by treatment (P<0.05). In conclusion, treatment with deslorelin had no apparent beneficial effect on testis development and delayed puberty when treatment was initiated at 3 mo of age. Staining for GATA-4 is a useful method for identifying and quantifying Sertoli cell nuclei in both pre- and post-pubertal bulls.