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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Livestock Bio-Systems » Research » Publications at this Location » Publication #432744
Research Project: Improving Lifetime Productivity in Swine using Systems Biology and Precision Management Approaches

Location: Livestock Bio-Systems

Title: Neuroendocrine suppression of testicular development in neonatal boars via subcutaneous implant

Author
item CRISPELL, LAURA - Tennessee University
item SOLOMON, CHLOE - Tennessee University
item KOKIMA, CHERYL - Tennessee University
item SUN, XIAOCUN - Tennessee University
item Lents, Clay
item FECTEAU, KELLIE - Tennessee University
item WHITLOCK, BRIAN - Tennessee University

Submitted to: Society of Theriogenology Annual Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 4/8/2026
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: In the United States swine industry, boars raised for pork are commonly castrated. By removing the testicles, the neonatal “mini-puberty” cannot occur, thus inhibiting sexual development to prevent boar taint and ensure consistent pork quality. In this study, a previously validated, and commercially available, sex-steroid based cattle growth implant [REVALOR-S implant (6 pellets; 120 mg trenbolone acetate, 24 mg estradiol), Merck Animal Health] was used in neonatal pigs to determine the effects it had on hypothalamic control of reproduction, specifically the kisspeptin neurons in the arcuate nucleus (ARC). We hypothesized that the implant would decrease ARC kisspeptin expression, serum luteinizing hormone (LH), and testicular size by the time the boar pigs were weaned [post-natal day (PND) 24]. Male neonatal pigs were administered one of three treatments [Castrate (n = 7), Control (gonadal intact, n = 8), or Implant (gonadal intact + 10 REVALOR-S implant pellets, n = 7)] at PND 3. Body weight was determined weekly, and blood samples were collected on PND 3 and 24. Brain and testicles were collected following euthanasia (PND 24). Immunohistochemistry of the ARC was completed to determine kisspeptin expression. Serum samples were quantified with radioimmunoassay to determine LH concentrations. The number of ARC kisspeptin neurons was suppressed in Implant (0.02±0.14 SE; p < 0.0001), while there was no difference between Control (11.85±1.05) and Castrate (13.74±1.10; p = 0.9996). There was a decrease in serum LH concentrations between PND 3 (5.72±1.33 ng/mL) and PND 24 (1.32±0.27 ng/mL) in Implant (p < 0.05). The ratio of testicular to body mass was decreased in the Implant group (0.17±0.01) compared to Control (0.93±0.07; p < 0.0001). These results indicate that the REVALOR-S implant was successful at suppressing the hypothalamic-pituitary-gonadal axis during the “mini-puberty," suggesting a non-surgical alternative to castration. The USDA is an equal opportunity provider and employer.