FEMALE REPRODUCTION BY DR. ALASTAIR SMITH
Spring has returned and so has the number of bitches on season. The female greyhound can cycle at any time throughout the year. However, there is an increase in the number of bitches cycling at this particular time. The bitch’s cycle can be divided into four stages: Proestrus: average 9 days (2-27). This is the beginning of the cycle. The vulva enlarges and there is blood stained discharge. The bitch will not accept the male. This is the time to get your veterinarian to take a pre-mating swab for infection. Oestrus: average 9 days (3-21). This is the period the female accepts the male for mating. The discharge is lighter in colour through to straw coloured. Natural mating or artificial insemination occur during this period. Ovulation occurs during this stage. Dioestrus (metoestrus): average 90 days. In an unmated bitch the hormones show levels similar to those in a pregnant bitch. Signs of a false pregnancy may develop. Anoestrus: average 2-7 months. This is the inactive period between cycles. The hormonal control of oestrus cycle begins in the brain in the hypothalamus. GnRH (gonadotrophin releasing hormone) is released. This acts on the pituitary gland to release LH (luteinising hormone) and FSH (follicle stimulating hormone). These in turn act on the ovary to stimulate the growth of the follicles and cause them to ovulate. Once the follicle is stimulated it starts to produce progesterone. The amount of progesterone produced increases dramatically at the time of ovulation. Once ovulation has occurred the empty follicle (now called the corpus luteum) continues to produce progesterone which maintains the pregnancy. Ovulation usually occurs during the oestrus period when the bitch is accepting the male. However, this is not always the case. Some bitches can ovulate earlier or later than expected. This can pose a problem to the owner and studmaster in trying to get these bitches in pup as the correct time to mate may not be obvious. Techniques for establishing the most effective time to mate include, relying on an experienced stud dog, visual changes in the bitch’s cycle, vaginal cytology and progesterone testing. An experienced stud dog can give the studmaster an indication of when the bitches are ready to mate. Bitches produce pheromones (smells) which are related to the stage of their cycle. Some dogs are sensitive and can pick the most likely time to mate by the scent of the bitch. This technique should be used as a guide as other scents (eg. Flea treatments) may put the dog off the bitch or other dogs may be so enthusiastic they do not care what stage of the cycle the bitch is at as they want to mate anyway. The hormonal changes in the bitches cycle induce physical changes which can be monitored. These include swelling of the vulva, bleeding and standing or flagging for the dog. The vulva usually swells at the beginning of the cycle (proestrus) and then reduces at the end of the cycle. The discharge will change throughout the cycle. Generally the colour will progress from a dark red through to a pink then to a clear or brown colour at the end of her cycle. The rule of thumb is that a good time to mate is when the colour has ‘paled off’ but is not clear or brown. However, experience is often needed to interpret these changes. The other issue with monitoring colour changes is that some bitches do not follow this rule of thumb. They may ovulate early when there is good colour and bleeding or later. These bitches can make life for the stud master more difficult. A more accurate way of testing a bitch’s cycle is to look at the changes in the cells within the reproductive tract. Again, as the hormones change during the cycle these cells change. A veterinarian or experienced/well trained studmaster can look at these cells on a microscope by taking a simple swab from the bitch. The cells change form as the cycle progresses. A large percentage of cornified cells (flat ‘cornflake-like cells’) is usually present during oestrus. Again, this method is not the most a accurate as every bitch can be different and the same bitch may differ between cycles. Progesterone testing is currently the easiest and most affordable hormone to monitor. By monitoring the elevation of this hormone one can ascertain the time of ovulation and mate accordingly. This test requires a small blood sample from the bitch on a daily or every second day basis. Repeat samples are essential, as the studmaster or veterinarian needs to see how the levels are changing on a day—to—day  basis to be accurate on determining the rise in the progesterone level. This is the most accurate way to time a bitch for mating. Some bitches frustrate their owners and future breeders by having incomplete cycles or failing to cycle at all. The bitches that fail to have pups may be classified into two groups: those that are cycling but not following the traditional rules or expectations, and those which are failing to cycle and ovulate. When assessing the bitch it is important to establish the most accurate history possible (ie how long was her last season, the interval between seasons, what signs did she show, when was she mated, and was the previous breedings successful?) The first group can be assessed on an individual basis. The use of progesterone timing is the key tool for dealing with these cases, as the oestrus period can be as short as three days or as long as three weeks. The use of progesterone tests allow the studmaster to determine the time of ovulation and mate correctly despite potentially conflicting physical signs the bitch may be exhibiting. For example, some of the bitches may even appear to be ‘going off’, but ovulation occurs after these physical signs and a successful mating is still possible if the progesterone rises and a mating or AI takes place. The second group are those bitches which fail to get in pup despite the best attempts of studmasters and breeders. These bitches may have false cycles where they do not ovulate despite the fact that they appear to have a normal cycle. Progesterone testing throughout the cycle will confirm this fact as the bitch will ‘go off’ but the progesterone level will fail to rise. This confirms the bitch has not ovulated therefore could not conceive any pups. Some of these bitches may have further medical concerns (eg. The formation of follicular cysts or low thyroid levels). This is when veterinary attention needs to be sought. The use of progesterone timing is of critical importance to ensuring the best chance of a successful mating. Those bitches which fail to cycle properly or at all may need medical assistance to maximise their chance of breeding. This may involve blood testing, hormonal treatments or surgery (cystic ovaries). If a bitch fails to cycle there are methods to induce a season. It should be noted that these protocols may not result in a fertile season but should start the bitch’s regular pattern (ie. 6-12 months). Mating can be undertaken during an induced season but should be accompanied with progesterone levels. Protocols used to induce a cycle in the bitch are based on modification of the stages of the cycle previously discussed: Elimination of proestrus: using short-term progestagens, this will stop oestrus and start an obligate period of anoestrus which is then followed by a natural oestrus. These medications are female hormones and can slow a race animal down. This is often a temporary prolonging of the cycle. Induction of luteolysis—shortening of the dioestrus  period. Drugs to stop the function of the corpra lutea on the ovary shorten the cycle so the bitch can cycle again more quickly. This method still relies on the bitch cycling and can still take months for her to come on. Shortening the anoestrus period. Prolactin inhibitors given during the anoestrus. Prolactin inhibitors given during the anoestrus period can shorten this period and induce a bitch to come on season. This is a technique used for treating greyhound bitches which may be having prolonged intervals between cycles. Stimulation of GnRH, LH and FSH. Combinations of hormonal treatments causing the release of GnRH, LH and FSH with or without the addition of oestrogen can be used to induce a fertile oestrus in bitches in the anoestrus phase of their cycle or have not cycled at all. Individual doses and exact protocols may vary for the individual bitch and veterinary advice should be sort in each case. The studmasters should also be notified so they can take the bitch’s circumstances into consideration when determining the time to mate. If a bitch is not destined for breeding then oestrus will need to be prevented, or else she could potentially lose six months a year from racing if she was to cycle twice a year. Although many medications are available for the suppression of oestrus, many of these have detrimental effects on the performance of the animal. Medications used range from: Female hormones (progestagens and oestrogens): which often have the effect of reducing the animal’s performance as well as medical problems (eg. Diabetes, cystic endometrial hyperplasia and pyometra, weight gain, lethargy, and increased appetite. They are options if other more traditional medications do not work/agree with the bitch. Some medications used with success include ethloestrenol (Nandoral) and some of the human contraceptive pills. Androgrens (male hormones): these can be administered via injections on a monthly basis or as an oral medication on a daily basis. These work well in 19 our of 20 bitches (1 in 20 may become sour and cranky). Some masculanisation may occur (clitoral enlargement, mucoid discharge from the vulva, increases to muscular strength and motivation/aggression may also occur). It should be noted that no method is 100% effective in all bitches. Also if the bitch is a potentially valuable breeding animal then any treatment should be undertaken with caution as long term use of hormones can result in delayed cycling and difficulties at a later time. These medications are restricted and must be dispensed by a veterinarian. This allows the potential use and side effects to be discussed and assessed on an individual basis. SANDOWN VETERINARY CLINIC DR. ALASTAIR SMITH AND ASSOCIATES LIGHTWOOD ROAD, SPRINGVALE VIC. 3171 PHONE: (03) 9547 6666 FAX: (03) 9548 4247