REMEMBERING reproduction lectures from my time at college requires extra effort over and above that needed for other subjects. Now, nearly 20 years later, I can recall that sinking feeling when “cornered” by the reproduction lecturer in the college Land Rover on a fertility visit, asking what I had remembered from the previous week’s lecture.
The question was always asked with a knowing smile. The problem was that reproduction lectures always fell on a Friday morning, and Dublin vet students traditionally went out on a Thursday night. Friday morning lectures unfortunately always took the hit, as evidenced by the empty rows.
So it was with great enthusiasm, and partly a delayed sense of guilt, that I jumped at the chance to attend one of the recent evening roadshows on Small animal reproduction in general practice – options and alternatives, hosted by Virbac Animal Health and presented at the Animal Health Trust by Angelika von Heimendahl, who runs a private reproduction referral service and is a clinical consultant at the Cambridge veterinary school.
Reproduction specialists are few and far between in the UK, but Angelika pointed out early in her presentation that many of the queries and problems presented by breeders can be solved through a thorough understanding of the reproductive cycle and are within the scope of general practices.
Rather than hide in the office when a breeder enters reception, she encouraged practices to embrace these clients, many of whom will become great advocates of the practice if they are on-side, and in most cases have a very realistic attitude to what is going on with their animal.
Whilst many do not have lots of money to spend, and few have insurance (as reproduction is normally excluded from policies), most are caring and knowledgeable pet owners who want to do the best for their pet.
The first half of Angelika’s presentation focused on helping to optimise conception and the use of diagnostic aids in pregnancy planning. She helpfully (for me) ran through a reminder of the physiology of reproduction and emphasised that the measurement of progesterone is probably the most useful tool in canine reproduction.
For those of you with a similar memory lapse to myself, just as a reminder, the bitch is non-seasonal mono-oestrus, cycling about every seven months. A period of pro-oestrus, signalled by physical and behavioural changes including swelling of the vulva and a serosanguinous discharge, usually lasts an average of nine days, but can range from 0-17 days.
During this time, follicles in the ovary, under the influence of follicle stimulating hormone (FSH) from the pituitary gland, increase in size and produce oestrogen, leading to cornification of the vaginal epithelial cells. The steroid hormone progesterone is produced in small quantities by maturing follicles at this time (and later by corpora lutea).
Oestrus which follows and is characterised by the receptivity of the bitch to mating, lasts on average nine days, but can range from 3-21 days. Luteinising hormone (also from the pituitary) during pro-oestrus luteinises the follicles prior to ovulation and then surges and peaks, stimulating ovulation.
At the same time, progesterone levels start to rise significantly from baseline values and at the time of the peak in LH levels reach about 1.52.5ng/ml (3-7 nmol/l). It is worth noting that once progesterone is starting to rise it doubles roughly every two days.
At ovulation, which takes place about two days after the LH peak, progesterone levels are 5-7ng/ml (1520nmol/l); this level is consistent, allowing this hormone to be used to help predict or confirm ovulation and help identify the ideal fertilisation period.
Progesterone continues to be produced by the corpora lutea and following the end of oestrus (on average about six days after ovulation) the bitch enters a di-oestrus phase which persists whether the bitch is pregnant or not.
Progesterone drops back to base levels 12-24 hours before parturition if the bitch is pregnant, with parturition 63 days after ovulation , or slightly longer if she is not pregnant. So again, measuring progesterone can be a very useful tool in predicting parturition or signalling when intervention may be necessary if the breeder raises concern that she is not showing any signs of whelping.
ELISA kits are available for inhouse progesterone testing but Angelika
emphasised that accuracy is vital in performing and interpreting the test. Remembering that the egg will take two days to reach maturation post ovulation, and then remain viable for two days after maturation, actually gives quite a long window of time to prepare for the mating.
A possible mating regime was suggested: given the fertilisation period is from ovulation plus one day until plus four days, then, if two matings are possible, plan for mating on ovulation plus one and plus three days (as male dogs have “super” sperm, surviving 5-7 days in a “good” dog) or ovulation plus two and plus four days. If one mating only is possible then ovulation plus two or ovulation plus three is suggested.
For progesterone testing, Angelika recommends starting on day five if no males are around, or if the breeder is not sure of dates, and then to space the testing (with the shortest interval to be 48 hours – daily testing is not needed) in a sensible way to maximise information and keep costs down.
Every other day testing is practical and should always be continued until ovulation is confirmed (don’t stop short at the pre-ovulation stage). Have a pen and paper to hand to count forward the days for ideal mating, not forgetting the two-day maturation period.
She felt that there was a place for vaginal cytology but that it needed to be done daily and needed experience in identifying cell types. Cells will be completely cornified throughout oestrus and will abruptly become non-cornified as soon as oestrus is finished. If white blood cells are seen, then it’s too late.
Pharmacological interventions
In the second half of her presentation, Angelika focused on pharmacological interventions relating to reproduction and went through some of the newer drugs available for the treatment of misalliance such as the synthetic progesterone antagonist Aglepristone and its mode of action.
Interestingly, off-label use of this drug can extend to non-surgical treatment of pyometra, induction of parturition in unwell females (e.g. in bitches with large litters or conditions such as diabetes or heart disease) and its use in pre-operative reduction in the size of mammary or vaginal tumours.
Licensed non-surgical contraceptives, such as the GnRH superagonist Deslorelin, available for entire male dogs, lend the breeder more flexibility in allowing effective temporary reduction (for six months on average) in testosterone and sperm count, with no long-term reduction in semen quality or male fertility following its use.
A scenario for its use with non breeders may be where the pet owner desires to see what effect castration might have on the dog’s temperament before committing to permanent castration through surgery.
Angelika noted that the UK now has the highest rate of neutering in the world for both male and female animals but urged vets to question whether for every non breeding individual this should be the default.
Neutering in European countries outside the UK is much less common and indeed is prohibited by law in places such as Scandinavia and Germany. There, females are either allowed to have seasons or are treated with GnRH analogues or progesterone.
Many owners do not have a problem with entire pets, and she recommended that rather than making neutering a blanket recommendation and part of the “package” of responsible pet ownership, vets should carefully discuss options with the client, discussing the pros and cons of neutering, their lifestyles, and help them to make an informed choice.
Advantages of neutering include fewer mammary and testicular tumours, along with a lower incidence of ovarian and prostate cancers. In some breeds, such as those where a higher rate of tumours such as osteosarcomas and haemangiosarcomas are seen, leaving them intact may decrease the risk of these cancers.
The American Society of Theriogenology also refers to a lower incidence of obesity and related problems such as diabetes and cranial cruciate rupture and fewer transitional cell carcinomas in entire animals. The decision to isn’t always black and white!
Overall the evening was truly enlightening and interesting, lending me confidence in an area I’d hitherto considered a “dark art”. So next time a breeder walks through the door, maybe I won’t be so scared.
