Artificial induction of lactation in cattle: initiation of lactation and estrogen and progesterone concentrations in milk.
Thirty heifers were given 11 subcutaneous injections of 5 mg estradiol benzoate and 200 mg progesterone every 3 d to develop their mammary glands. Three days later groups of animals were treated with 1) 20 mg dexamethasone twice, 2) 500 micrograms cloprostenol thrice, 3) dexamethasone and cloprostenol, 4) oxytocin 4 IU six times, or 5) no further injections. Two further groups of six heifers each (6 and 7) were treated in a manner similar to groups 1 and 3 except the dose of estrogen to develop their mammary glands was doubled to 10 mg/3 d. Six lactating first calf heifers were controls (8). The proportion of animals lactating, combined milk yield for each group (kg), and mean days lactated were 1) 5/6, 3831, 142; 2) 1/6, 912, 195; 3) 6/6, 4898, 194; 4) 3/6, 1066, 128; 5) 1/6, 293, 154; 6) 6/6, 6109, 130; 7) 6/6, 6265, 130; and 8) 6/6, 19, 190, 251. The lactogenic response to dexamethasone and oxytocin is similar to that in sheep, but the response to cloprostenol indicates a species difference. Intensive blood sampling before and after injection of hormones, intended to trigger lactogenesis, showed that plasma prolactin rose to peaks above 210 ng/ml in cows of groups 2, 3, and 4 and were unchanged from the base below 40 ng/ml in groups 1 and 5. Monitoring of steroids after induction treatment showed estradiol-17 beta ranged between 35 and 400 pg/ml and 20 to 80 pg/ml in mammary secretion and plasma and progesterone concentrations were less than at diestrus.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002417:Cattle; D003008:Cloprostenol / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D004958:Estradiol / Q000032:analysis / Q000097:blood / Q000494:pharmacology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D066298:In Vitro Techniques; D007774:Lactation / Q000187:drug effects*; D008892:Milk / Q000032:analysis; D010121:Oxytocin / Q000494:pharmacology; D011247:Pregnancy; D011374:Progesterone / Q000032:analysis / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood
D003008:Cloprostenol; D011374:Progesterone; D004958:Estradiol; D010121:Oxytocin; D003907:Dexamethasone; D011388:Prolactin; D006854:Hydrocortisone