Ovarian morphometrical evaluation to assess reproductive activity suppression in heavy weight finishing gilts immunized against gonadotropin-releasing hormone. (May 2021)

• Record Type: Journal Article
• Authors: Cardoso, Lucas; Rodrigues, Lucas; Fontes, Dalton; Allison, Jim; Chiarini-Garcia, Helio; Almeida, Fernanda
• Is Part Of: Research in veterinary science. Volume 136(2021)
• Page Start: 519
• Page End: 526
• Publication Date: 2021-05
• Subjects: Follicular development -- Oestrus suppression -- Ovarian morphology -- Pigs; Veterinary medicine -- Periodicals; Veterinary Medicine -- Periodicals; Médecine vétérinaire -- Périodiques; Médecine vétérinaire -- Recherche -- Périodiques; Diergeneeskunde; 636.089
• DOI: 10.1016/j.rvsc.2021.04.005
• Languages: English
• ISSNs: 0034-5288

Abstract

Abstract: It is known that immunizing gilts against gonadotropin-releasing hormone (GnRH) is an efficient castration method that increases their growth performance. However, it is still unknown the ovarian histophysiology outcomes after this procedure. Therefore, the aim of this study was to investigate in detail, using morphological and morphometrical methods, changes in the ovarian structure that result in the suppression of ovarian activity, as well as to gain knowledge on the ovarian structure to assist in ovarian histopathological diagnoses. Seventy-two pre-pubertal finishing gilts were allocated to two experimental groups: immunized (IC; n = 36; gilts which received two injections of 2 mL of Vivax® - one at 15 and another at 19 weeks of age) and control (CT; n = 36, females which received two saline injections following the same protocol). All gilts were euthanized at 25 weeks of age and the ovaries of 5 gilts from each experimental group collected for biometrical and histomorphometrical analysis. IC gilts showed higher body weights, but smaller ovaries compared to CT females. In addition, the number of small follicles (≤ 2 mm) on the ovarian surface was higher, while no large follicles (> 6 mm) nor corpora lutea were found in the ovaries of IC gilts. Histomorphometrical analysis revealed that IC females showed higher numbers of quiescent and active primordial, primary, pre-antral and final stage atretic follicles. Moreover, follicle size, antrum diameter and area of the granulosa layer from mature follicles were smaller in IC gilts. Collectively, these results demonstrate that the efficacy of immunization against GnRH is related to the blockage of follicular recruitment and selection, thus suppressing reproductive activity in finishing gilts. Highlights: Immunocastration drastically reduced ovarian size and weight. Immunized gilts had higher numbers of less developed (primordial and primary) and atretic follicles. Antrum and granulosa area of mature follicles were reduced in immunized gilts. Immunocastration blocked follicular recruitment and selection in finishing gilts. Establishment of the differential diagnosis between reproductive activity suppression and pathological folliculogenesis.