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Artificial Induction of Lactation in Cattle: Initiation of Lactation and Estrogen and Progesterone Concentrations in Milk

Department of Agriculture, Box 1231, Bunbury, Western Australia 6230

W. J. Fulkerson

Department of Agriculture, Launceston, Tasmania 7250

G. B. Martin

Department of Animal Science and Production, Institute of Agriculture, University of Western Australia, Nedlands, Western Australia 6009

Christine Gow

Animal Production Division, C.S.I.R.O., Prospect, New South Wales 2149, Australia

ABSTRACT

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 µg 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-17ß 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. Low estrogen in the induction regimen for groups 1 to 5 reduced abnormal estrous behavior, but resulting milk production was 20% of normal. Increased estrogen improved milk production but also increased adverse side effects. Further refinement of the low dose steroid treatment is required.