Synthetic prostaglandin for cattle and horses.
Cattle. Single or repeat doses of 2 mL (500 microgram) by intramuscular injection. Therapeutic uses. A single intramuscular dose of Estromil is likely to be highly effective in the following clinical conditions of the cow.
1. Suboestrus or nondetected oestrus (NDO). This condition occurs in heavy yielding cows, usually at peak lactation, which have normal ovarian cyclicity but in which behavioural manifestations of oestrus are either very mild, transient or absent. Such animals can be treated with Estromil following diagnosis of a corpus luteum by rectal palpation, and then closely observed for oestrus. Those showing heat should be inseminated. Some animals may have been treated during the refractory period of the cycle and therefore will not respond. Animals now showing heat should receive a further single injection 11 days after the first and be inseminated 72 and 96 hours later.
2. Termination of normal but unwanted pregnancies. Pregnancy can be terminated from 1 week after conception until day 150 of gestation. Before 100 days gestation, abortion can be induced rapidly and efficiently. Between 100 and 150 days of gestation results are less reliable, probably because a proportion of cattle may become progressively less dependent on the corpus luteum for the maintenance of pregnancy. Abortion should not be induced after day 150 of gestation. Treated animals should be kept under supervision until expulsion of the foetus and the placental membranes is complete, as 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 eighth day, a second injection should be given.
3. Termination of abnormal pregnancy. Removal of mummified foetus: death of the conceptus may be followed by its dehydration and degeneration. Induction of luteolysis at any stage of pregnancy will result in the expulsion of this mummified foetus from the uterus into the vagina. Manual removal from the vagina may be necessary. Normal cyclical activity should then follow.
Hydrops of the foetal membranes: pathological accumulation of placental fluids (hydramnios or hydrallantois) can cause several physiological complications and death. Surgical drainage is not usually successful in alleviating the condition. A single dose of Estromil may be used to induce parturition in such cases; success has been achieved as early as the sixth month of pregnancy.
4. Chronic endometritis (pyometra). Damage to the reproductive tract at calving or postpartum retention of the placenta frequently lead to infection and inflammation of the uterus. Acute or subacute endometritis occurring shortly after parturition may require both local and systemic antibiotic treatment and this often results in resolution of the condition. However, under certain circumstances, the endometritis may progress until at a few weeks postpartum the uterus is very swollen, of a soft doughy consistency and full of purulent discharge. This is characterised by a lack of cyclical oestrus behaviour and the presence of a persistent corpus luteum. This condition can be successfully treated by induction of luteal regression. Where necessary, treatment may be repeated at 10 to 14 day intervals.
5. Induction of parturition. Induction of parturition should take place as close to the predicted calving date as possible and not more than 10 days before. Induction should not be attempted before day 270 of gestation, measured from the confirmed day of conception. All treated animals must receive adequate supervision. In common with all other methods of shortening the gestation period, a higher than usual incidence of retention of the foetal membranes is to be expected. It is now recognised that there may be a reduced survival rate in calves born as a result of early induction. Any increased mortality is due to lack of viability as a result of prematurity rather than any effect from the prostaglandins.
6. Ovarian luteal cysts. Where cystic ovaries associated with persistent luteal tissue and absence of oestrus are diagnosed, Estromil has proven effective in correcting the condition and bringing about a return of cycling. Accurate diagnosis is essential if completely satisfactory results are to be achieved.
Controlled breeding programs. The luteolytic activity of Estromil can be harnessed to control the breeding patterns of cattle. A variety of treatment regimens exists from which it is possible to choose the most appropriate for the characteristics and objectives of each particular individual, group or herd. Estromil can be used to complement oestrus detection input or animals may be bred ?on schedule? during critical times of the breeding season, without reference to oestrus detection. Use one of the following programs.
Dairy herd. 1. To control oestrus in the individual animal giving better control of the calving index by allowing artificial insemination (AI) without oestrus detection. The number of cows culled as barren is consequently reduced.
2. To synchronise oestrus in groups of cows to promote management of the herd in groups of suitable size for feeding, AI and drying off. The chances of maintaining a strictly seasonal calving herd are improved and the number of barren cows at the end of the breeding program is reduced.
3. To permit the use of AI in dairy heifers which, in turn, allows the speeding up of the breeding program, the use of a bull known to produce few dystocia problems, better control of heifer management, and ?steaming up? prior to calving.
Beef herd. 1. To facilitate the use of AI improving the progeny through the use of genetically superior bulls. The problems of oestrus detection are avoided and the labour involved in carrying out an AI program is reduced by allowing groups of cattle to be presented instead of single animals.
2. To permit better management at conception and calving. The calving pattern is altered, resulting in greater average weight of calves at weaning. The peak calving period can be forecast more accurately in relation to other events in the farm calendar and there is an improved potential for ?flushing? the cows prior to AI.
Horses. A single intramuscular injection of 0.5 to 1.0 mL for animals up to 400 kg bodyweight. 1.0 to 2.0 mL for horses weighing 400 kg and above. Estromil, as a potent luteolytic agent, causes regression of the corpus luteum in mares in a variety of circumstances. Luteolysis is usually followed by oestrus, appearing two to four days after treatment, with ovulation during the induced oestrus. This sequence of events is seen, for example, in mares treated with Estromil during the dioestrus (progestational) phase of the oestrus cycle, but it should be noted that there is a refractory period of four to five days after ovulation when mares are not responsive to the luteolytic action of prostaglandins.
Estromil has a wide margin of safety, and has no deleterious effect on foals conceived and born as a result of mares being covered at the induced oestrus. This property of shortening the life span of the corpus luteum makes Estromil of clinical value in the following situations.
1. Induction of luteolysis following early foetal death and resorption. About 8 to 10% of all mares which conceive lose the conceptus during the first 100 days of pregnancy. Persistence of luteal function in the ovary precludes an early return of oestrus. Treatment before day 45 is recommended. After that time no response may be obtained due to the presence of circulating pregnant mare serum gonadotrophin (PMSG).
2. Termination of pseudopregnancy. Some mares covered at normal oestrus and subsequently found to be empty (but not having lost or resorbed a conceptus) display clinical signs of pregnancy. These animals are said to be ?pseudopregnant?.
3. Treatment of lactation anoestrus. Failure of lactating mares to cycle again for several months after exhibiting an early ?foal heat? can be avoided in most cases. Some variability does, however, occur.
4. Barren and maiden mares. Some of these animals will be found on examination to have a functional corpus luteum and are either suffering from abnormal persistence of luteal function or are simply failing to exhibit normal oestrus behaviour (?silent heat?) while ovarian cyclicity continues.
5. Synchronisation of oestrus. Under some circumstances this may be a desirable objective in stud management. Treatment during dioestrus usually induces oestrus after two to four days, with ovulation occurring eight to twelve days after treatment.
6. Nomination of the time of service. Mares may be brought into oestrus at will, simply as an aid to successful and economic management of stallions during the breeding season.
Controlled cattle breeding programs. A. Day 1: give Estromil injection. Day 11: give Estromil injection.
B. Palpate. All animals with corpus luteum receive Estromil injection.
C. Day 1: give Estromil injection. Day 11: all animals not bred receive Estromil injection.
D. Detect heat for 6 days and breed. Day 6: all animals not bred receive Estromil injection.
Notes. Breed at usual time, relative to detected heat; or at about 72 hours and 96 hours post-injection; or perform mass AI at 72 hours, with re-insemination of those in oestrus over the next 2?3 days. Best results are obtained where heat detection is utilised. This is generally assisted by the use of tail paint. Identification of animals is important. Conception rate may be about 20% less if insemination is carried out en masse 72 hours after injection with no re-insemination. Estromil can also be used in systems which include other treatment regimens, e.g. CIDR.
Intravenous injection. Administration to pregnant animals where the foetus is not to be aborted, since luteolysis at some stages of gestation will result in the loss of the foetus. Administration to mares suffering from acute or subacute disorders of the gastrointestinal tract, mares suffering from acute or subacute respiratory disease (this is a precautionary measure because in some species of animals, dosing with prostaglandins can result in acute respiratory distress), pregnant mares, since luteolysis at some stages of gestation will result in the loss of the foetus.