Studies on parturition in dairy cattle.

Levels of estrone，estradiol-17，progesterone and oxytocin in the peripheral plasma during late pregnancy and parturition in Holstein cows were measured.Estrone levels remained low until4weeks prepartum(155pg/ml)，began to rise from4weeks until1day prepartum(155-2271pg/ml)，and reached a peak at parturition.Then the levels fell to 197pg/ml at 1 day postpartum。Changes in the plasma estradiol-17levels generally resembled those for estrone levels，but the estradiol-17levels were only10-21%as compared to those of estrone levels.Progesterone levels remained high until 2 days prepartum(o.71 ng/ml)，began to fall at 1 day prepartum and 0.75 ng/ml at parturition，and was 0.23 ng/ml at 1 day postpartum.On the day of parturiton，the levels of estrogens and progesterone remained approximately constant from the beginning of opening labor pains until 1hr postpartum。Oxytocin levels rose abruptly on the day of parturition in most of cows.The levels in cows showing weak pains were about half of those in normal cows.Changes in rectal temperature，heart and respiration rates，rising of tail head，and sizes of udder，teat and vulva were determined during the preparturient period in order to study these items could be utilized for the estimation of the onset time of parturiton。Fall in rectal temperature below 39.0°C and marked increase of udder size was useful for the prediction of parturition time.Changes in behavior during preparturient period were also studied.Times of standing-up，standing time and tail movement were determined。These items may be worth noting as for the prediction of onset time of parturition.Effect of-adrenoceptor agonist(Clenbuterol)on parturition time and uterine activity during parturition was examined in rats.After administration of-adrenoceptor agonist，the uterine contraction decreased and deriveries interrupted in rats.The efficacy of-adrenoceptor agonist was not so clear in cows.

Levels of estrone, estradiol-17 , progesterone and oxytocin in the peripheral plasma during late pregnancy and parturition in Holstein cows were measured. Estrone levels remained low until 4 weeks prepartum (155 pg/ml), began to rise from 4 weeks until 1 day prepartum (155-2271 pg/ml), and reached a peak at parturition. Then the levels fell to 197 pg/ml at 1 day postpartum. Changes in the plasma estradiol-17 levels generally resembled those for estrone levels, but the estradiol-17 levels were only 10-21% as compared to those of estrone levels. progesterone levels remained high until 2 days prepartum (o.71 ng/ml), began to fall at 1 day prepartum and 0.75 ng/ml at parturition, and was 0.23 ng/ml at 1 day postpartum. On the day of parturiton, the levels of estrogens and progesterone remained approximately constant from the beginning of opening labor pains until 1 hr postpartum. Oxytocin levels rose abruptly on the day of parturition in most of cows. The levels in cows showing weak pains were about half of those in normal cows.Changes in rectal temperature, heart and respiration rates, rising of tail head, and sizes of udder, teat and vulva were determined during the preparturient period in order to study these items could be utilized for the estimation of the onset time of parturiton. Fall in rectal temperature below 39.0゜C and marked increase of udder size was useful for the prediction of parturition time.Changes in behavior during preparturient period were also studied. Times of standing-up, standing time and tail movement were determined. These items may be worth noting as for the prediction of onset time of parturition.Effect of -adrenoceptor agonist (clenbuterol) on parturition time and uterine activity during parturition was examined in rats. After administration of -adrenoceptor agonist, the uterine contraction decreased and deriveries interrupted in rats. The efficacy of -adrenoceptor agonist was not so clear in cows.