P.M.S.G. is a freeze-dried powder and the dosage administered is expressed in international units (i.u.), which is then converted to volume. There are different kinds of P.M.S.G., for example 6000 i.u. Chonogest or 5000 i.u. Novormon and it is ot utmost importance to consult with your AI Centre for the correct dosage. P.M.S.G. must be dissolved in a sterile solution immediately before use.
P.M.S.G. is sensitive to temperature changes and must be kept cool (5 – 10 ° C). Once the solution has been made, it must be protected against sunlight and heat and used within 48 hours. Accuracy is essential, and administration is intramuscularly (the thick rump muscle behind the hip bones and in front of the pin bones is easier to reach than the thigh muscle).
It is essential to use P.M.S.G. to ensure good synchronisation. At high doses it can stimulate multiple ovulations, which could lead to multiple births. ` The dosage of P.M.S.G. can be lowered when a ewe flock has a history of high conception rates, a good percentage of multiple births on first cycle, is in a good nutritional status and is being mated during its natural mating season. When the opposite conditions are prevalent in a flock with a poor breeding history, deprived nutritional status and outside its natural mating season, the dosage may be increased.
Breeders wanting to increase the number of multiple births can also inject a higher dose.
For Merino ewes we recommend 300 i.u., for heavy mutton breeds 360 – 480 i.u. and for Angora goats 180 – 240 i.u. – depending on age, nutritional status, breeding history and breeding season. It is important for the breeder and inseminator to communicate about this result and reach a final decision.
P.M.S.G. is always administered intramuscularly and at the same time of sponge withdrawal.
The time between sponge withdrawal and insemination is very important, since ovulation takes place from about 56 – 60 hours after sponge withdrawal and it is important to inseminate before that, especially when fresh semen is used. Maiden ewes usually ovulate earlier and some differences between breeds and seasons may occur.
When CIDRs is used, ewes come on heat and ovulate four hours earlier than is the case with sponges.