The optimal mating time in the bitch

Question 1

The optimal time for mating is likely to be?

Answer 1

During or immediately preceding the fertilisation period, and the period of peak fertility for natural matings ranges from 1 day before to 5 or 6 days after the LH surge. Determination of the time to breed could therefore be based upon methods for estimating the time of the LH surge.

Question 2

The LH surge is a good marker of ascertaining peak fertility but why is it so hard to measure?

Answer 2

Measurement of plasma concentrations of LH is a reliable and accurate method of determining the optimum time to mate. However, there is no readily available commercial assay for canine LH, and at present measurement requires radioimmunoassay, a technique that is time-consuming and expensive. An enzyme-linked immunosorbent assay (ELISA) has recently been described for the measurement of LH concentration in fox plasma, but has yet to be evaluated in the dog and a key challenge in measuring LH is the fact that concentrations peak and return to basal within a short period of time, necessitating daily sampling.

Question 3

What would be a good hormone to measure that would point to a time near the LH surge and peak fertility?

Answer 3

Plasma progesterone concentrations begin to increase towards the end of pro-oestrus at the time of the LH surge. The progesterone is produced by luteinising follicles, and therefore, serial monitoring of plasma progesterone concentrations allows anticipation of ovulation. Since progesterone concentrations rise slowly prior to ovulation daily sampling is not necessary. Commercial test kits designed to measure the concentration of plasma progesterone by ELISA are available. These kits have been shown to be useful for predicting the optimum mating time in the bitch. Progesterone concentration may also be measured using this method on whole blood and vaginal fluid. Furthermore, it has been demonstrated that progesterone can be measured in faeces allowing the potential for non-invasive monitoring of the time of ovulation.

Question 4

What can be used to monitor the oestrus cycle?

Answer 4

Examination of exfoliative vaginal cells is commonly used to monitor the oestrous cycle.

During pro-oestrus, increased plasma oestrogen concentrations cause thickening of the vaginal mucosa, which becomes a keratinised squamous epithelium.

Question 5

How can vaginal cells be monitored?

Answer 5

Vaginal epithelial cells may be collected either using a moistened swab or by aspiration.

Question 6

The relative proportions of different types of epithelial cells can be used as a marker of the endocrine environment. Several methods for staining of cells and various indices of cornification and keratinisation have been suggested as markers for the stage of the cycle. In general, the fertile period can be predicted by?

Answer 6

calculating the percentage of epithelial cells that appear cornified using a modified Wright–Giemsa stain.

Question 7

Howd does oestrus appear in vaginal cytology?

Answer 7

Polymorphonuclear leucocytes are absent from the vaginal smear during oestrus because the keratinised epithelium is impervious to these cells. Their reappearance during late oestrus reflects the breakdown of this epithelium. The return of polymorphonuclear leucocytes to the vaginal smear has been used by some workers as an indicator of the time of optimum fertility.

Question 8

When should breeding be attempted according to vaginal cytology?

Answer 8

Breeding should normally be attempted throughout the period when more than 80% of epithelial cells are cornified . Whilst this is a good guide, some bitches reach peak values of only 60% cornification, whilst in others there may be two peaks of cornification . Some bitches demonstrate poor cellular changes in the vaginal smear and sometimes polymorphonuclear leucocytes may be found throughout the entire oestrous period; the extent of these variations has not been quantified.

Question 9

Evaluation of the anuclear cell index of cells aspirated from the cranial vagina was found to?

Answer 9

• Increase the pregnancy rate and litter size of a group of bitches compared with a similar group mated only on the basis of the onset of proestrus.
• The technique is particularly useful for bitches with irregular oestrous cycles and those with prolonged pro-oestrus or prolonged oestrus.

Question 10

How does anoestrus appear on cytology?

Answer 10

Question 11

How does pro-oestrus appear in cytology?

Answer 11

Question 12

How does oestrus appear in cytology?

Answer 12

Question 13

How does early met-oestrus appear on cytology?

Answer 13

Question 14

Discuss Canine Vaginoscopy: Cyclical Changes?

Answer 14

The hormonal changes which occur during the onset of proestrus, oestrus and the early luteal phase have a direct effect upon the vaginal epithelium resulting in an initial proliferation and oedema of the mucosa, a subsequent reduction in oedema, and finally sloughing of the epithelium. These changes can be readily detected with vaginoscopic examination.

Question 15

How does the vagina appear on vaginascope in prooestrus?

Answer 15

During proestrus, increased plasma oestrogen concentrations cause thickening of the vaginal mucosa which becomes a keratinised squamous epithelium.

This is essentially a mechanism to protect the normally thin vaginal mucosa from potential trauma at the time of mating. Under the influence of oestrogen there is also significant oedema of the vaginal wall.

Question 16

How does the vagina appear on vaginascope in oestrus?

Answer 16

A subsequent decline in oestrogen and slight increase in plasma progesterone initiates oestrus at which time the bitch will allow mating. The reduction in oestrogen is associated with a reduction in oedema. The rise in plasma progesterone concentration (a result of pre-ovulatory luteinisation) and the low oestrogen: progesterone ratio causes a surge in luteinising hormone (LH) from the pituitary gland. Most ovulations commence 48 hours after peak LH concentrations are reached. High concentrations of progesterone occur approximately 7 days after ovulation, after which time the proliferated epithelium starts to slough.

Question 17

Endoscopically at the onset of proestrus the mucosa becomes?

Answer 17

thickened and oedematous due to the increase in plasma concentrations of oestrogen. The mucosal folds therefore appear greatly enlarged, thickened and oedematous. Serosanguinous fluid can be observed within the lumen and may be seen to exit from the cervix. This is a stark change in appearance from the relatively thin, flat and dry mucosa noted during anoestrus. Furthermore, there is a considerable change in colour of the epithelium which changes from being red with clearly visible vessels to a pink or pink/white colour.

Question 18

As proestrus progresses, the mucosal surface become?

Answer 18

progressively less pink and typically appears white in colour, because the thickened mucosa prevents the underlying capillaries (that were visible during anoestrus) from being seen.

Question 19

In late proestrus or early oestrus, at approximately the same time as the LH surge, there is a?

Answer 19

progressive shrinking of the folds that is accompanied by further pallor. These effects are the result of an abrupt withdrawal of oestrogen. Oestrogen concentrations decline rapidly during and following the LH surge. Subsequently, over the next several days, mucosal shrinkage is accompanied by gross wrinkling of the mucosal folds and they now develop a distinctly angulated appearance but remain a dense cream to white color. The epithelial peaks become sharp-tipped and irregular in appearance. The mucosa also starts to look drier, and in many bitches there is a change to a clear/creamy colour of any discharge originating from the cervix.

Question 20

At the end of the fertile period there is?

Answer 20

rapid shedding of the epithelial surface. Sometime passage of the endoscope lifts large sheets of cells from the vaginal wall. Complete shedding of the epithelium is usually completed within 48 hours. The mucosal folds become less distinct and are clearly softer and flaccid. The surface of the mucosa at this time becomes variegated in colour with white patches mixed with areas of red-coloured thin epithelium

Question 21

Finally, as the luteal phase progresses (whether pregnant or non-pregnant) there is a?

Answer 21

reduction in the diameter of the lumen, similar to that seen in the anoestrus bitch. Initially there is apparent contraction of the folds producing a rosette appearance. Thereafter the flat, dry and red epithelium is similar to that observed during anoestrus.

Question 22

Describe each phase and how it appeards in vaginal endoscopy?

Answer 22

Inactive Phase (I)

This phase is characterised by a thin, red and dry mucosa with low and flattened mucosal folds.

Oedematous Phase (O)

This phase is characterised by a thickened and oedematous mucosa which appears turgidly swollen, rounded and grey/white in colour. Folds with this appearance are designated ‘O’

Shrinkage Phase (S)

This phase is characterised by a thickened mucosa which is normally white in colour but where there is reduced turgidity with progressive furrowing, wrinkling and indentations. The mucosal fold profile is however still rounded rather than angular. The progressive nature of this phase means that the early changes are designated ‘S1’ and the later changes ‘S2’

Angulated Phase (A)

This phase is characterised by a thickened mucosa which is normally white in colour but where there is significant reduced turgidity such that in profile the mucosal folds have progressive shrinkage and angulation such that the peaks are sharp-tipped and irregular in appearance. The mucosa is wrinkled and shrunken in appearance. The progressive nature of this phase means that the early changes are designated ‘A1’ and the later changes ‘A2’ and ‘A3’

Declining Phase (D)

This phase is characterised by a progressive decline in the size of the mucosal fold profile. Early in the phase (designated ‘D1’) there is a flaccid appearance to the mucosal fold profile. Subsequently, the folds become more rounded (‘D2’) and there is sloughing of the cornified layers of the epithelium (‘D2’ and ‘D3’), resulting in a thin mucosa of variegated colour with flattened folds and a rosette-appearance to the mucosa (‘D4’)

Inactive Phase (I)

The decline phase is followed by a return to a phase characterised by a thin, red and dry mucosa with low and flattened mucosal folds. This appearance is also designated ‘I’. There may be more debris present at this stage than found in Phase I prior to the onset of proestrus.