Breeding Management of Bitches
Bitches are unique to all of the domestic species we work with. Phylogenetically dogs sit near bears, cats and rabbits which are all induced ovulators (ovulate in response to a mating), however bitches are spontaneous ovulators.
Additionally, bitches ovulate an oocyte (egg) that is stuck in a stage of division which is not stimulated to complete until after ovulation has occurred. Unlike other species breeding is not timed to occur at ovulation, it is timed to occur after ovulation. This makes timing bitches for breeding the most difficult of all of the domestic species that we work with.
Techniques used for timing breeding
There are 3 tools we have in our toolbelt for working out the best time to breed a bitch. What we use and when is dependant on the type of breeding (natural mating, fresh semen artificial insemination, chilled semen artificial insemination or frozen semen insemination) and how the cycle is progressing. The tests we use are vaginal cytology, progesterone measurement and vaginoscopy, all of which are indirect tests (indirectly telling us what the ovary and oocytes are doing). As they are indirect tests it is imperative to do multiple tests to look at changes in the results (this is the art side of breeding management). We use these tests to work out when ovulation is occurring and complete and in turn work out the best time to get the semen in.
Vaginal cytology is done by placing a moistened cotton swab into the caudal vagina of the bitch, collecting some of the cells and then rolling them onto a microscope slide, then staining them and looking at the cell types under the microscope. As the cycle progresses the cells change from looking like fried eggs to looking like cornflakes. This allows us to broadly categorise the stage of the cycle of the bitch, but not work out an accurate breeding date. Many breeders and veterinarians promote sending these swabs off to the laboratory for culture, however this process is both inaccurate and unnecessary and promotes the inappropriate use of antibiotics so is not recommended.
Progesterone is a hormone produced by the cells that surround the oocytes in the ovary. It is the one hormone required to maintain pregnancy in the bitch, and during the oestrus cycle of the bitch it changes in number relative to the ovulatory process in the ovary. Progesterone is a good indicator of time to breed, however one test is not enough, it is important to look at changes in numbers and use progesterone to confirm ovulation is complete. Pinpointing ovulation also allows for an accurate whelping date to be determined. There are many options for measuring progesterone nowadays, however measurement of progesterone is sensitive to the collection method, storage and handling of the blood sample, the tube the blood is collected into and the machine in which the progesterone level is read. The most reliable machines for measuring progesterone are those that are only used for measuring hormones (even some brands of these can be inconsistent), machines that measure other biochemical and haematological constituents are unreliable for progesterone assessment.
Vaginoscopy is a technique where we use an endoscope to look at changes which occur in the caudal vagina through the oestrus cycle. Vaginoscopy indirectly tells us what the blood level of oestrogen is in the bitch. Oestrogen is toxic to sperm and reduces after ovulation. With fresh semen and chilled semen, we use a lot of strong sperm to inseminate so oestrogen itself is not an issue, however frozen semen is fragile, and we use low numbers of sperm, so it is important to ensure oestrogen levels are low before inseminating. In most cases vaginoscopy is reserved for frozen semen. Progesterone measurement has a 30-40% error margin in the test, and frozen semen possibly only lives for 30 mins-2 days in the reproductive tract of the bitch (fresh semen lives for up to 10 days), so vaginoscopy helps us to reduce this error margin and maximise success with frozen semen.
LH Assays are used by some to try and work out the LH surge. Luteinising hormone is produced in the brain and there is a surge release to cause ovulation. I don’t use this test as I don’t think it adds any benefit to the other forms of testing. The LH surge can be quite short, and it requires daily, or ideally twice daily, blood draws. Even if the LH surge is identified, counting days from this to work out the insemination date will not result in good conception rates.
Artificial Insemination Techniques
There are 3 commonly performed artificial insemination techniques in dogs, vaginal artificial insemination, endoscopic assisted transcervical insemination (TCI), and surgical laparotomy/surgical implant insemination. It must be noted that when bitches mate naturally, the semen is ejaculated directly into the uterus, not into the vagina.
Vaginal insemination is performed by blindly passing a catheter (tube) into the vagina of the bitch, hoping to get up near the cervix, inseminating the sperm to bathe the cervix and hoping enough sperm traverse the cervix to pass up to the oviduct (fallopian tube) to fertilise the oocytes (eggs). The success rate of vaginal insemination is low compared to TCI (below).
Endoscope assisted transcervical insemination (TCI) is performed using an endoscope to pass a catheter through the cervix of the bitch and allows deposition of semen into the uterus of the bitch. TCI when performed correctly has a 40% higher pregnancy rate than vaginal insemination with fresh sperm. TCI requires minimal restraint and no anaesthesia, so is as close as we can get to a natural mating artificially. TCI has a 20% higher pregnancy rate than surgical insemination (below), which I published in 2014.
Surgical insemination is performed under a general anaesthetic and the abdomen is cut open to place semen in the uterus. There are risks with both anaesthesia and surgery with this method and it is less successful than TCI, and for this reason I do not perform this procedure. There are no benefits to surgical insemination in the bitch, and soon this procedure will become illegal in Australia as it is in some European countries and the United Kingdom.
Artificial Insemination in Cats
Artificial insemination in cats is a newly developing technique as unfortunately it has not been developed for as long as our canine friends. Semen collection in cats must be done under a general anaesthetic using electroejaculation, however the semen can be inseminated into the queen via TCI (using a different type of endoscope to the dogs). TCI in queens requires general anaesthesia, however no surgery is required. It is best to synchronise the cycle of the queen to maximise success with artificial insemination.
