The effect of early postnatal treatment with a gonadotropin-releasing hormone agonist on the developmental profiles of testicular steroid hormones inthe intact male pig
Pa. Sinclair et al., The effect of early postnatal treatment with a gonadotropin-releasing hormone agonist on the developmental profiles of testicular steroid hormones inthe intact male pig, J ANIM SCI, 79(4), 2001, pp. 1003-1010
Three studies examined the effects of early postnatal treatment with a GnRH
agonist on plasma concentrations of testosterone, dehydroepiandrosterone s
ulfate, 16-androstene steroids in fat and salivary glands, androstenone in
fat and plasma, and testicular development of intact male pigs. The first s
tudy involved 45 7-d-old pigs assigned to three treatment groups: 1) boars
administered 100 mug/kg of Lupron depot, 2) boars administered 200 mug/kg o
f Lupron depot, and 3) control boars receiving a saline carrier. The second
study involved 20 7-d-old pigs assigned to two treatments: daily injection
of 200 muL of 0.5 mg/mL Lupron from d 7 to 35 and controls treated with sa
line. The third study involved a total of 100 animals assigned to 10 groups
of 10 based on their age at slaughter. These groups were subdivided into o
ne of two treatments: 1) boars injected with 200 muL of 0.5 mg/mL of Lupron
from d 3 to 35 and 2) control boars injected with saline. Testicular stero
id hormone concentrations in plasma decreased (P < 0.01) within 7 d of GnRH
agonist treatment. Following cessation of treatment, steroid levels increa
sed to control levels and remained constant until the final rise at 5 mo. P
lasma testosterone levels in the 100 <mu>g/kg depot treatment group were hi
gher (P < 0.05) than that of the 200 <mu>g/kg and control group at 164 d of
age. There were no differences between treatments (P > 0.05) in testicular
steroid hormone levels at the end of study 2 or 3. There were no differenc
es (P > 0.05) in concentrations of 16-androstene steroids in salivary gland
s between any of the treatment groups at market weight in studies 1 and 2.
Fat androstenone levels measured in the third study ranged between 0.6 mug/
g and 4.2 mug/g at 7 to 28 d of age. Treatment with GnRH agonist decreased
plasma steroid levels and testicular development; however, by d 60 testicul
ar size and weight were at control levels and remained similar until 180 d
of age. The results of these studies indicate that daily administration of
a GnRH agonist significantly decreased testicular development and steroidog
enesis only during treatment, but testis growth and steroidogenesis had ret
urned to control levels by 60 d of age in male pigs. Suppression of the ear
ly postnatal rise in testicular steroid hormones did not affect growth perf
ormance or steroid hormone levels at 5 to 6 mo of age.