Estrogens and piglet viability. I. Serum estrogen concentrations in piglets

An experiment was conducted to establish estrogen (Es) levels in piglet serum up to 13 h after birth. Treated piglets were given an injection of estradiol benzoate into the vena cava immediately after birth. Control piglets were similarly injected with saline solution. Blood samples were obtained frequently for monitoring Es levels. Each sample was analyzed for estrone (E1), estrone sulphate (E1SO4) and estradiol-17 beta (E2) by radioimmunoassay. Immediately after birth, Es declined at a very fast rate for 4 h and thereafter declined slowly until 9 h, when a small recovery occurred. There were no differences (P greater than .05) in the initial concentrations of Es between the control and treated groups. Injected estradiol benzoate did not significantly increase serum Es concentration (P greater than .05) by 5 min postinjection in treated animals, but sustained a trend showing higher level of Es than the control until 4 h. At birth, E1SO4 was the Es with the highest concentration in piglet serum, followed by E1 and E2. The sharpest decline after birth occurred in E1SO4, which fell to lower values than E1 by 3 h. We conclude that an undetermined catabolic system for Es allows the piglet to eliminate or transform Es to other compounds.