Breeding of the Bitch (Female Dog)

Breeding of the Bitch (Female Dog) is involves careful planning and understanding of oestrus cycle to ensure successful conception.

The most common problem encountered by veterinarians working in canine reproduction is the “potentially” infertile bitch.

When should Breeding Begin?

The simple goal in any breeding program is to have sufficient sperm numbers present in the uterus and oviducts to achieve the optimal chance for fertilization of mature eggs. Mature oocytes are fertilized 3 to 8 days following LH surge. Behavioural observation, use of vaginal cytology, vaginoscopy and serial progesterone concentration could be used together to enhance the chances of a bitch being bred at the correct time.

Methods of Breeding

Methods of breeding include:

• Out-crossing
• In-breeding
• Line breeding

Out-crossing is the mating of two dogs within the same breed that are less closely related than the breed average.

In-breeding occurs when closely related dogs are breed such as parents and offspring or brother and sister.

Line breeding (which is a form of in-breeding) occurs with the repeated use of 1-2 dogs (usually males) for breeding to increase a certain trait.

The problems with in-breeding are that it increases the manifestation of undesirable traits.

Goal in Breeding Programme

The simple goal in any breeding program is to have sufficient sperm numbers present in the uterus and oviducts to achieve the optimal chance for fertilization of mature eggs.

Mature occytes are typically fertilized during the 3 to 8 days following the luteinizing hormone surge, representing a period beginning 24 to 48 hours after ovulation of primary immature oocytes.

Using reliable, clinically practical methods for estimating the day of the LH surge can be quite valuable. These criteria include:

1. Behaviour observation
2. Vaginal cytology
3. Vaginoscopy
4. Hormone assays
5. Ultrasonography

When used together they enhance the chances of a bitch being inseminated at the proper times.

Further, normal sperm are known to survive and retain the capacity for fertilizing mature oocytes within the uterus of the bitch for at least 4 to 6 days, and in some instance for as long as 11 days.

Using this information, a breeding program can be offered to a client with reasonable confidence of success.

1. Behaviour Observation

Observation of the bitch‘s response to a male is an inexpensive, straight forward, and reliable means of determining when to begin and when to end the breeding phase. If the female stands for the male, breeding should begin regardless of the colour of vaginal discharge, vaginal exfoliative cytology or the day of cycle. On day 5 to 6 the bitch should be brought into contact with male for approximately 10-20 min. This should be repeated every second or third day. Breeding should begin whenever the bitch is willing to breed and should be continued every other day.

2. Vaginal Cytology

Vaginal exfoliative cytology provides a good reflection of rising plasma estrogen concentrations. Full estrogen effect is seen on cytology as greater than 80% of epithelial cells being of the superficial or cornified type. This is the day when the bitch should be brought to the male. Vaginal smears should be monitored beginning with the second or third day of proestrus.

Once breeding begins, it should be allowed to continue until the bitch refuses to breed. It is recommended to breed the dog every second, third or fourth day of estrus.

3. Vaginal Endoscopy

Vaginoscopy can be used to aid in timing natural breeding. Vaginal mucosa in proestrus appears rounded and oedematous. “Wrinkling” of “Crenulation” of mucosa is associated with LH surge. This is the time to begin breeding. Breeding should be continued throughout the phase of maximal mucosal crenulation, seen as angulated folds of vaginal mucosa with sharp profiles. Breeding should be discontinued when the vaginal mucosa again becomes flaccid and smooth, with patchy red and while surface which is observed 6 to 10 days following LH surge.

4. Hormone Assays

Serum Progesterone

In hospital test kits are available for measuring serum concentrations of progesterone as <3, 3–10 ng/ml and greater than 10 ng/ml. serum should be assessed beginning 3 or 4 days after onset of proestrus and should be continued every other day. At the time of ovulation the level of blood progesterone rises dramatically & ovulation takes place when values of progesterone are between 4 and 10 ng/ml. Matings should be done at this time.

It is important to know that the time of ovulation, the ova are primary oocytes and require 48 hours to mature. Hence a second mation should be done 48 hours later to achieve maximum litter size.

LH Assay

Measurement of the peripheral plasma concentration of LH is a reliable and accurate method for determining the optimum time to mate. In most countries there is no readily available commercial assay for canine serum LH, and at present measurement requires radioimmunoassay. This method is time-consuming, expensive and there is frequently a delay in obtaining the results, because samples are assayed in batches in service laboratories. Should LH concentration be measured, critical matings or insemination can be planned between four and six days after the LH surge.

At least one ELIZA assay kit for measuring LH in canine serum has been marketed for ovulation timing (Status-LH, Synbiotics). The test is stored at room temperature and has a relatively short shelf-life. The kit may not be accurate if used beyond the expiration date, or if the foil packet containing the test device and pipette is opened well before the test is to be run. The preferred sample is serum. The sample should not be lipemic or hemolyzed. The test should be run the same day the serum is collected. If that is not possible, the serum should be refrigerated, not frozen, until the test can be run.

Because duration of the LH peak averages about one day in bitches, samples must be drawn daily, at about the same time of day. Because of the tests short shelf-life, necessity of daily testing, and the requirement of assessing progesterone to verify accuracy, this assay is rarely used in practice.

5. Ultrasonography

Ultrasound is another recent method of detecting ovulation wherein the only sign of ovulation is gradual thickening of follicle walls due to luteinization. Interestingly the number of follicles that are visible on ultrasound does not correlate well with the number of oocytes that actually ovulate. This is because 20-30% of canine follicles are “poly ovular oocytes”. Because of these challenges, we do not use ultrosonography to monitor bitches for breeding. However, it is useful to diagnose cystic ovarian disease, pregnancy or pyometra.