Plasma levels of several androgens and estrogens from birth to puberty in male domestic pigs

Abstract

Plasma concentrations for several androgens and estrogens were determined in male domestic pigs from birth to eight months of age. Samples (N = 6) of blood were collected from Yorkshire males at weekly intervals from birth to four weeks, and thereafter at monthly intervals to eight months. Radioimmunoassays were done without extraction from plasma for dehydroepiandrosterone sulphate, androstenedione and estrone sulphate. Other steroids were measured after solid-phase extraction, separate elution of unconjugated and conjugated fractions, and solvolysis of sulpho-conjugated steroids (testosterone, 5α-androstane-3β, 1 7β-diol, epiandrosterone, 19-nortestosterone and estradiol-177β). All steroids showed a peak in plasma levels at 2–4 weeks after birth. Concentrations remained low from 2–5 months and rose markedly thereafter. Most steroids were present in much greater quantities as sulpho-conjugated compounds. Concentrations of testosterone sulphate and testosterone were similar (9.4 μmol/l) at three weeks but the sulphated form predominated after six months of age. This study shows that during postnatal development the testes of the domestic pig are remarkably active in steroidogenesis with a peak at 2–4 weeks after birth. Also, the range of steroid products seen at this stage is comparable to that shown by the mature boar.

Stimulation of Sertoli cell proliferation: defining the response interval to an inhibitor of estrogen synthesis in the boar

“…Our data suggest that proliferation during the immediate postnatal interval is not sensitive to aromatase inhibition but becomes responsive after the first 3 weeks of life. This is a developmental interval during which endogenous circulating estrogen concentrations are declining naturally (Ford 1983, Schwarzenberger et al 1993) and may define the important period of Sertoli cell proliferation in a physiological context also. The reduced estrogen concentrations in tissues and serum of letrozole-treated boars confirmed that the lack of response during this interval was not due to a failure of the drug to inhibit estrogen synthesis, suggesting that there must be a change in the responsiveness that affects Sertoli cell proliferation itself.…”

Biochemical, nutritional and genetic effects on boar taint in entire male pigs

“…The production of androstenone and other testicular steroids is controlled by the neuroendocrine system, particularly by the lutenizing hormone (LH), which is under stimulatory control of gonadotropin-releasing hormone (GnRH). A transient activation of the hypothalamic-pituitary-gonadal axis during early postnatal life (approximately 2-4 weeks of age) results in an increase in levels of circulating testicular steroids including androstenone (Bonneau, 1982;Schwarzenberger et al, 1993;Sinclair et al, 2001). Otherwise, the biosynthesis of androstenone is low in young pigs and gradually increases along with other testicular steroids at sexual maturity (Gower, 1972;Bonneau, 1982).…”

“…Sexual maturity and steroidogenic potential is best assessed by measuring plasma levels of sex steroids, such as estrone sulphate (Schwarzenberger et al, 1993;Sinclair et al, 2001) or free estrone in fat (Zamaratskaia et al, 2005d). Sexual maturity may also be assessed by age/ weight or size of secondary sex glands of the pigs (e.g.…”

Early vaccination with Improvac®: effects on performance and behaviour of male pigs

“…This is in accordance with Baumgartner et al (2010) and Rydhmer et al (2010), who reported less activity for surgically castrated pigs already at the beginning of the growing period. The reasons for this behaviour are not clear, particularly given that Schwarzenberger et al (1993) found that gonadal hormones between entire male and castrated pigs at this early, pre-pubertal stage do not differ. However, Berry and Signoret (1984) reported that neonatal castration affected behaviour by elimination of sex play.…”