Effects of immunization against LHRH and treatment with trenbolone acetate on reproductive function of beef bulls and steers

Authors: Geary, Thomas; WELLS, K - Ohio Agricultural Research & Development Center; DEAVILA, D - Washington State University; DEAVILA, J - Washington State University; CONFORTI, V - University Of Brazil; MCLEAN, D - Washington State University; Roberts, Andrew; Waterman, Richard; REEVES, J - Washington State University

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2011
Publication Date: 7/1/2011
Citation: Geary, T.W., Wells, K.J., Deavila, D.M., Deavila, J., Conforti, V.A., Mclean, D.J., Roberts, A.J., Waterman, R.C., Reeves, J.J. 2011. Effects of immunization against LHRH and treatment with trenbolone acetate on reproductive function of beef bulls and steers. Journal of Animal Science. 89:2086-2095.

Interpretive Summary: Immunization against LHRH (or GnRH) has been used for immune-sterilization in cattle previously. The objectives of this study were (1) to evaluate the ability of trenbolone acetate (TBA) administered in tandem with LHRH immunization to suppress reproductive function in beef bulls and (2) to examine the effects of LHRH and androgen (TBA) signaling on pituitary function. In order to address these objectives, 44 Angus x Hereford crossbred calves were utilized in a 2 x 2 x 2 factorial treatment structure, with castration, LHRH immunization, and TBA administration as treatment factors. Five animals were used in each treatment group not receiving LHRH immunization and six animals were used in each treatment group receiving LHRH immunization. Animals immunized against LHRH received a primary injection and two booster injections of LHRH antigen on d 0, 42 and 196 respectively. Animals treated with TBA were implanted on d 224. Mean serum LHRH antibodies increased after each booster for immunized animals, but were negligible in non-immunized animals throughout the experiment. Scrotal circumference (P < 0.05) and serum testosterone concentration (P < 0.0001) were decreased in LHRH immunized bulls compared to non-immunized bulls by d 168 and 84 of the experiment, respectively. Treatment with TBA tended (P = 0.07) to decrease serum testosterone. Testes weight at harvest were decreased (P < 0.0001) for LHRH immunized (242 ± 41g) compared to non-immunized bulls (752 ± 45g). Both LHRH immunization and castration resulted in decreased anterior pituitary stores of LH and FSH (P = 0.0007). There was no effect of TBA on mean pituitary LH and FSH concentrations (P > 0.10). Immunization against LHRH decreased expression of LH ß-subunit, and common a-subunit genes (P < 0.0001). Castration increased expression of LH ß-subunit, and common a-subunit genes (P = 0.02). There was also an interaction between TBA and LHRH immunization (P = 0.04) on the expression of the common a-subunit gene. Castration and LHRH immunization both decreased HCW (P = 0.01) and ribeye area (P = 0.04), and increased marbling score (P = 0.03) compared to non-immunized bulls. In summary, LHRH immunization suppressed reproductive function in bulls, and resulted in carcass characteristics similar to steers. Immunization against LHRH also decreased synthesis and storage of LH and FSH. Expression of the LH ß-subunit and storage of both LH and FSH were dependent on LHRH stimulation. Androgen (TBA) may play a role in synthesis, but not storage, of LH and FSH.

Technical Abstract: The objectives of this study were (1) to evaluate the ability of trenbolone acetate (TBA) administered in tandem with LHRH immunization to suppress reproductive function in beef bulls and (2) to examine the effects of LHRH and androgen (TBA) signaling on pituitary function. In order to address these objectives 44 Angus x Hereford crossbred calves (mean weight = 225 ± 2 kg; mean age = 187 ± 6 d) were utilized in a 2 x 2 x 2 factorial treatment structure, with castration, LHRH immunization, and TBA administration as treatment factors. Five animals were used in each treatment group not receiving LHRH immunization and six animals were used in each treatment group receiving LHRH immunization. Animals immunized against LHRH received a primary injection and two booster injections of ovalbumin-LHRH-7 fusion protein on d 0, 42 and 196 respectively. Animals treated with TBA were implanted on d 224. Mean serum LHRH antibodies increased after each booster for immunized animals, but were negligible in non-immunized animals throughout the experiment. Scrotal circumference (P < 0.05) and serum testosterone concentration (P < 0.0001) were depressed in LHRH immunized bulls compared to non-immunized bulls by d 168 and 84 of the experiment, respectively. Treatment with TBA tended (P = 0.07) to decrease serum testosterone. Testes weight at harvest were decreased (P < 0.0001) for LHRH immunized (242 ± 41g) compared to non-immunized bulls (752 ± 45g). Both LHRH immunization and castration resulted in decreased anterior pituitary stores of LH and FSH (P = 0.0007). There was no effect of TBA on mean pituitary LH and FSH concentrations (P > 0.10). Immunization against LHRH decreased expression of LH ß-subunit, and common a-subunit genes (P < 0.0001). Castration increased expression of LH ß-subunit, and common a-subunit genes (P = 0.02). There was also an interaction between TBA and LHRH immunization (P = 0.04) on the expression of the common a-subunit gene. Castration and LHRH immunization both decreased HCW (P = 0.01) and ribeye area (P = 0.04), and increased marbling score (P = 0.03) compared to non-immunized bulls. In summary, LHRH immunization suppressed reproductive function in bulls, and resulted in carcass characteristics similar to steers. Immunization against LHRH also decreased synthesis and storage of LH and FSH. Expression of the LH ß-subunit and storage of both LH and FSH were dependent on LHRH stimulation.Androgen (TBA) may play a role in synthesis, but not storage, of LH and FSH.