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Goat placental lactogen was partially purified from a medium collected after placental tissue incubation. The data obtained by disc electrophoresis and isoelectric focusing experiments, as well as by means of radioreceptor assay methods, provide evidence of the similarity between the goat and ovine placental lactogen.

SUMMARY A method for the bioassay of oxytocin in the lactating rat mammary gland in vitro is described. The changes in transparency induced by oxytocin in a flat segment of the gland are recorded by means of a CdS photoresistor and a simple Wheatstone bridge. The sensitivity of the assay in routine use is about 0·5–10 μu. oxytocin, the index of precision being about 0·1.

Milk production of dairy cows in 14 herds was increased by 3 -8-32'l % by the administration of recombinant methionyl bovine somatotropin (bST) in a sustained-release vehicle at 14 d intervals at 40-94 d post partum. A greater response in multiparous than in primiparous cows was found in cows turned out to graze spring pasture. Administration of recombinant bST resulted in elevated plasma bST during the first 9 d after injection. Clinical characteristics such as respiration, heart rate and body temperature were unaffected by bST treatment, as were blood erythrocyte and leucocyte counts, haemoglobin concentrations and haematocrit values. Plasma levels of glucose, free fatty acids, urea and P, and serum alanine aminotransferase and aspartate aminotransferase were not affected by bST treatment, and acetone was not detected. No adverse effects of bST on general health, infection status of mammary glands, mastitis incidence and reproduction were found.Recombinant DNA technology has opened the way for the production of large quantities of polypeptides. As the use of recombinant bovine somatotropin (bST) could have an important impact on dairying, research on bST efficacy and safety in experimental and commercial dairy herds has been stimulated in many countries, including Czechoslovakia, where a high proportion of cows are in large state or cooperative farms. Diets for cows are based mainly on roughage and moderate amounts of concentrates, and herd management practices are often poor. A major current research interest is whether use of bST can significantly improve milk production under the conditions on Czech commercial dairy farms.The objective of the present investigation was to examine the effects of recombinant bST in a sustained-release vehicle on lactational performance, general health and mastitis incidence in dairy cows kept under different conditions in different parts of Czechoslovakia.