Estrumate, a synthetic prostaglandin, is a potent luteolytic agent for use in cattle and horses. Cloprostenol is structurally related to Prostaglandin F 2? (PGF2?). Both cause functional and morphological regression of the corpus luteum (luteolysis). Luteolysis is usually followed by a return to oestrus 2 to 4 days after treatment (with normal ovulation). Estrumate is specific in its luteolytic action, it is ineffective when there is not a corpus luteum present. For example, there is a refractory period of 5 to 6 days after ovulation when animals are insensitive to the luteolytic effect of prostaglandins. Estrumate has a wide safety margin. There is no deleterious effect on progeny conceived at the oestrus resulting from treatment with Estrumate. ESTRUMATE IN CATTLE The life cycle of the corpus luteum (CL) is terminated by the release of the uterine luteolysin. Thus an exogenous luteolytic agent such as Estrumate can effectively shorten the cycle length, provided it is administered at times when a fully functional corpus luteum is present. There are short periods in the cycle when the system is insensitive. These are the periods directly preceding and directly following oestrus. That is, the 4 to 5 day period in the late luteal/early follicular phase when the old corpus luteum is regressing and the 5 to 6 day period after ovulation when the new corpus luteum is developing. Between these periods there is a 12 day period when the fully functional corpus luteum will respond to Estrumate. Controlled Breeding Programmes Before a programme is planned, the farmer and veterinarian should discuss the expected results and limitations of the programme, reviewing the herd’s breeding history, herd health and nutritional status to decide if it is practical in the particular circumstances. For any successful controlled breeding programme using prostaglandins: • Cows and heifers must be normal, non-pregnant and cycling (an examination should be performed) • Cattle must be in good breeding condition and on an adequate or increasing plane of nutrition. • Proper programme planning and record keeping are essential (animals must be identified). • If artificial insemination is used it must be performed by competent inseminators using high quality semen. • Oestrus observation is important, this is greatly assisted by use of tail paint. • It is important to understand that Estrumate is effective only in animals with mature corpus luteum (ovulation must have occurred at least 5 days prior to treatment). Cattle which respond to a single prostaglandin injection will normally do so within 6 days of treatment. Please refer to Estrumate publications for options on different programmes. Therapeutic uses Several reproductive problems in cattle associated with luteal function will respond to luteolytic treatment with Estrumate. A single dose of Estrumate is likely to be highly effective in the following circumstances: • Sub-oestrus (or non-detected oestrus, or silent heat) Sub-oestrus is that condition when the animal shows no clinical signs of heat but in fact normal cyclic ovarian activity is present. If rectal palpation indicates a corpus luteum on the ovary, the cow will usually respond to a 2mL injection of Estrumate by displaying heat 2 to 5 days later. Animals treated in the refractory period of the cycle will not respond. Animals not showing heat should be examined first, they may have lapsed into anoestrum. If it is appropriate they should receive a second Estrumate injection 11 days after the first and be inseminated 72 and 96 hours later whether observed in oestrus or not. • Termination of early pregnancy Pregnancy can be terminated from one week after conception until the 150th day of gestation. Before 100 days gestation, abortion can be induced rapidly and efficiently, but between 100 and 150 days of gestation results are less reliable. Treated animals should be kept under supervision until the foetus and foetal membranes are expelled. An occasional animal may develop metritis following abortion. Most cows will abort in 3 to 5 days, if an animal has not aborted by the 12th day a second Estrumate injection should be given. • Termination of abnormal pregnancy 1. Removal of mummified foetus. If the corpus luteum is present, induction of Luteolysis with Estrumate will result in the expulsion of the foetal remains into the vagina in 3 to 5 days. 2. Abnormal conditions near parturition - Vaginal prolapse: Recurring vaginal prolapse can be a problem in late pregnancy which can be treated with Estrumate (2mL i/m) to induce parturition. - Hydrops of foetal membranes: Pathological accumulation of placental fluids, hydramnios or hydrallantois can cause severe physiological complications or death. A single injection of Estrumate usually results in the presentation of a live calf in late pregnancy. Success has been achieved as early as the 6th month of pregnancy. • Chronic purulent endometritis (pyometra) This condition may be successfully treated with a single dose. Acute or sub-acute endometritis may require both local and systemic antibiotic treatment. However, induction of luteal regression by treatment with Estrumate usually results in evacuation of the uterus in 3 to 4 days allowing antibiotic treatment. Occasionally some cases with extreme endometrial damage may require 2 or even 3 treatments with Estrumate at 10 day intervals. • Luteal Cysts Estrumate has proven effective in correcting the condition and bringing about a return of cycling 2 to 4 days later. Rectal palpation 7 to 10 days later should reveal whether regression is complete. Accurate diagnosis is essential if completely satisfactory results are to be achieved. • Induction of parturition Estrumate may be used in a planned calving programme as a 2mL dose 7 to 12 days after depot corticosteriod. All treated animals must receive adequate supervision. Induction closer to the predicted calving date is more likely to maximise calf survival because of reduced viability of the very premature calf. After day 270 of gestation (excluding Bubalus spp. and Bos indicus where the normal gestation is longer) cows treated with Estrumate usually calve within 48 hours. However the range can extend from less than 24 hours up to one week. Common side effects of induction: • Retained foetal membranes • Calf mortality • Pre-partum oestrus