An implant can be placed to bring the jill out of season , but caution must be used if the jill has been in season for some time , due to the initial hormonal surge that can prolong oestrus and bone marrow suppression . Care must also be taken when using deslorelin in an in-heat jill if she presents with early signs of hyperoestrogenism and hypoplastic anaemia [ 9 ] .
Goericke-Pesch and Wehrend [ 10 ] conducted a small study on seven jills in season for at least 4 weeks and found a reduction in vulva size within 1 – 2 weeks following administration of a 4.7 mg Suprelorin implant , indicating that ovulation had occurred [ 10 ] . Oestrus can remain suppressed for up to 32 months [ 10 ] . When placed before the breeding season , the implant led to the suppression of reproductive function for 698 ± 122 days ( monitored by clinical examination and hormone levels ); sexual behaviour was suppressed for 637 – 872 days [ 11 ] . However , in practice , suppression lasts around 1.5 – 2 years when using a 4.7 mg implant and 3 – 4 years with a 9.4 mg implant [ 12 ] . The author has experienced a 4.7 mg implant lasting 3.5 years when implanted in a female ferret in the early stages of season .
Van Zeeland et al . [ 13 ] suggest that it is advisable to place a new implant every year , based on the minimum duration of effectiveness . However , biennial replacement may be sufficient in the majority of ferrets [ 13 ] . In the author ' s experience , many owners will wait until the first signs of heat ( i . e . a swollen vulva ) to replace the implant . Owners may decide to place a Suprelorin implant , as opposed to surgical neutering , to reduce the risk of ACD . It should be noted that the author has seen a case of ACD in her own implanted ferret . Caution must be used when placing an implant in a female ferret outside the breeding season , as implanted females frequently show a temporary fertile heat after treatment . Therefore , the female should be separated from entire males until the vulva has returned to normal size [ 14 ] .
Human chorionic gonadotropin
Human chorionic gonadotropin ( hCG ) is a hormone that stimulates the production of gonadal steroid hormones by stimulating the corpus luteum of the ovary to produce progesterone . LH triggers ovulation and hCG can substitute for LH in this function . hCG stimulates ovulation and should be administered at least 10 days after the onset of oestrus [ 1 ] , stimulating ovulation 35 hours after injection in 95 % of cases , followed by anoestrus for 40 – 60 days , during which time the jill will go into pseudopregnancy [ 9 ] . Oestrus will terminate within 7 days of the administration of hCG in 95 % of jills . A reduction in vulva size should be seen within this time [ 15 ] . In some cases , a repeat dose is needed . Anaemia is linked to prolonged oestrus in ferrets , so a packed cell volume ( PCV ) measurement is advised to check for anaemia . Ferrets with a PCV of > 25 % have a good prognosis and respond well to treatment with hCG ; ferrets with a PCV of < 25 % carry a fair to guarded prognosis [ 9 ] .
Administration of GnRH
The pre-ovulatory LH surge can be mimicked indirectly by stimulating endogenous LH release with the administration of GnRH ( 20 μg ), given intramuscularly 10 days after the onset of oestrus [ 1 ] . As with the use of hCG , these drugs will induce a pseudopregnancy , with the jill returning to heat after this time . Multiple injections of GnRH may sensitise the ferret to the drug , resulting in anaphylactic reactions shortly after administration [ 1 ] . It is important to note that after treatment with hCG or GnRH , owners will need to consider medical or surgical treatment to prevent ovarian activity .
Breeding the jill
Ovulation is induced by neck gripping and pressure on the cervix during mating , and generally occurs 30 – 40 hours after this time . The swelling of the vulva associated with oestrus decreases several days after ovulation .
The gestation period is around 42 days . The jill gives birth to an average of eight kits but may have as many as 18 . Hairless rings develop around the jill ' s teats 1.5 weeks before giving birth . The jill may go back into season within 2 weeks after weaning if the breeding season has not ended .
If the jill does not nurse her litter or if the kits die , a new oestrus may be observed 8 weeks after mating [ 2 ] . The same interval between mating and return to oestrus occurs in cases of abortion or pseudopregnancy [ 2 ] . In some situations ( e . g . a small litter of up to four kits ) the jill may return into oestrus while nursing [ 2 ] ; in this case , it would be preferable to leave the ferret nursing and interrupt oestrus after the weaning period .
Please note : this article does not promote the breeding of ferrets as a solution to prolonged oestrus in females .
Conclusions
It is vital to avoid illness associated with prolonged seasons in female ferrets . There are many options available to prevent or terminate oestrus in these patients . Many are used off licence , and this should be fully explained to the owner .
Veterinary professionals should be aware of the options available for treating female ferrets and be able to discuss treatment plans with owners , taking into consideration the owner ' s individual situation , the duration of season in the presented ferret , and the risks associated with each treatment option .
If surgical neutering is chosen to prevent oestrus , then this should be done in a way that reduces the risk of adrenal disease in this species .
50 Veterinary Nursing Journal