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

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