Immunization of sheep against GnRH early in life: effects on reproductive function and hormones in ewes

Abstract

Groups of Merino ewe lambs were immunized against GnRH either soon after birth (prepubertal) or around puberty (peripubertal) with a prototype commercial preparation and were studied over the following 2 years to determine the long-term effects on reproductive development, function and hormone concentrations. At least 60% of the GnRH-immunized ewes in either treatment group did not experience oestrus and possessed small uteri and small ovaries that lacked follicular development. Growth rates of immunized and control ewes were similar throughout the study. Compared with the increase in plasma LH and FSH concentrations with age in control ewes, the concentrations of these hormones in immunized animals were lower and remained relatively constant from 46 to 90 weeks of age. Plasma FSH concentrations were particularly suppressed in immunized ewes and were significantly (P < 0.05) lower than the control values of 61 and 90 weeks of age. LH release after injection of 1 microgram GnRH at 90 weeks of age was either absent or suppressed in immunized ewes compared with controls. The findings suggest that the lack of GnRH stimulation and consequent deprivation of gonadotrophins, early in the life of ewes, may result in some degree of permanent impairment of hypothalamic and/or pituitary function.

GnRH immunocontraception of male cats

“…In most reports, a series of prime-boost treatments was given and the follow-up period was short. GnRH immunization resulted in decreased testosterone, LH, and progesterone concentrations, testes size, estrus cycling, libido, aggression, and androgen-related taint in calves [18][19][20][21][22], piglets [23][24][25][26][27], and lambs [28][29][30]. Similar responses were observed in adult stallions [31] and cows [32].…”

Variation in estradiol level affects cortical bone growth in response to mechanical loading in sheep

“…The low-E 2 animals were vaccinated [4·ml intramuscularly (IM)] on day 1 and day 22 against GnRH (gonadotrophin releasing hormone) using Protherics immunoneutering vaccine (Protherics PLC, Cheshire, UK). In previous studies, vaccination against GnRH suppressed production of gonadal steroids, including E 2 (Brown et al, 1995). The high-E 2 animals were implanted on day 1 with subcutaneous capsules that release 61.5·g·E 2 ·day -1 (Encore © , VetLife, Inc, Norcross, GA, USA).…”

Vaccination against gonadotropin-releasing factor (GnRF) with Bopriva significantly decreases testicular development, serum testosterone levels and physical activity in pubertal bulls

“…The suppression of reproductive function using an anti-GnRF vaccine has been demonstrated in numerous studies in cattle [3][4][5][6][7][8][9][10][11][12][13], sheep [10,[14][15][16][17][18][19][20][21], pig [22][23][24][25][26][27][28], horse [29][30][31][32][33][34] and in wild animals [35][36][37][38][39].…”