The effects of in utero androgen exposure on growth characteristics in sheep

Hastie, P. , Evans, N. and Robinson, J. (2008) The effects of in utero androgen exposure on growth characteristics in sheep. In: 6th International Congress on Farm Animal Endocrinology, Roanoke, Virginia, USA, 14-16 Oct 2008,

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Abstract

Over the last 20 years experimental evidence has indicated that the environment of the fetus, and the substances to which a developing animal is exposed, can have a significant impact on its growth and development, both in utero and later in life. Recent studies have demonstrated that exposure of fetal sheep to exogenous male hormones (androgens) during a relatively short critical window of development (d30-90 of 147d gestation) leads to abnormalities in growth in males and females, concomitant with virilization and reproductive dysfunction in females. The mechanisms underlying these prenatally programmed effects, especially those on growth, are poorly understood. In addition, it is unclear whether the abnormalities in growth are mediated via the actions at androgen or estrogen receptors. The aim of this study was to characterize patterns of growth in male and female Poll Dorset lambs that were exposed to twice weekly injections of (i)vegetable oil (control); (ii) testosterone propionate (TP; 200mg/week); or (iii)dihydrotestosterone (DHT; 200mg/week), between d30-90 of gestation. Two androgens were used as TP can be aromatized (androgenic and estrogenic actions) whereas DHT is nonaromatizable (androgenic actions only). Animals were weighed at birth, and weights, measures of stature (crown-rump length, wither height, girth) and backfat thickness (assessed by ultrasound) were obtained at 1, 2 and 3 months of age. A subset of animals (2 males and 2 females per group) was euthanazed at birth to obtain measures of bone formation. At birth DHT males (3.4±0.35; n=9) and females (3.2±0.31; n=14), and TP females (3.5±0.23; n=17), were significantly (P<0.01) lighter than TP males (4.6±0.29; n=11) and control males (4.5±0.33; n=7)and females (4.3±0.15; n=14), which were not different. At 1, 2 and 3 months of age TP males were significantly (P<0.05) heavier than all other groups, while by 2 months of age, DHT females were significantly (P<0.05) lighter than all other groups. Consequently, average daily gain (ADG) from birth to each measured time period was significantly (P<0.01) greater in the TP males compared to all other groups. Similarly, by 2 months of age, TP males had a significantly (P<0.05) greater crown-rump length and girth in comparison to all other groups, while overall DHT animals were significantly (P<0.05) smaller in length, height and girth in comparison to control and TP animals. Backfat thickness over the loin was significantly (P<0.05) less in DHT animals, in comparison to control and TP animals, which were not different. Examination of lambs euthanazed at birth demonstrated that all 4 DHT animals had compromised long bone growth and exhibited marked signs of osteoporosis (via radiographic analysis) compared to control and TP animals. These results demonstrate that prenatal exposure to androgens results in sexually dimorphic effects on prenatal and postnatal growth. In addition, the results indicate that the actions of androgens to programme different aspects of growth are mediated via both androgenic and estrogenic receptors.

Item Type:Conference Proceedings
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Robinson, Dr Jane and Hastie, Professor Peter and Evans, Professor Neil
Authors: Hastie, P., Evans, N., and Robinson, J.
Subjects:S Agriculture > SF Animal culture > SF600 Veterinary Medicine
College/School:College of Medical Veterinary and Life Sciences > Institute of Biodiversity Animal Health and Comparative Medicine
College of Medical Veterinary and Life Sciences > School of Veterinary Medicine
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