Effect of prenatal testosterone treatment on nitrogen utilization and endocrine status of ewe lambs

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Abstract
Thirty-eight pregnant Suffolk ewes were assigned randomly to a control group or implanted with approximately 2 g of testosterone propionate (TP) when they were between d 40 and 60 of gestation. Implants were removed 3 wk prior to lambing. Five ewe lambs born to implanted ewes and ten ewe lambs born to nonimplanted ewes were utilized in this experiment Ram lambs were not used in this trial. No differences (P >.10) were observed for fecal, urinary and total N excretion and amount of N absorbed. Nitrogen retained (percentage of N intake and g/d) was higher (P <.05) in prenatally androgenized ewe lambs than in control ewe lambs. Plasma insulin concentrations averaged 99% higher (P <.05) in prenatally androgenized ewe lambs. Plasma insulin-like growth factor I (IGF-I) concentrations averaged 29% higher (P <.06) in ewe lambs treated prenatally with testosterone. Nonesterified fatty acid (NEFA) concentrations averaged 41% higher (P <.05) in prenatally androgenized ewe lambs. Significant (P <.05) treatment × time effects were observed in plasma thyroxine, glucose and urea N concentrations of prenatally androgenized vs control ewe lambs. These significant modifications in the plasma metabolite and endocrine status could be an important element of the physiological mechanism(s) by which prenatal androgenization improves growth performance and leanness of ewe lambs.

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