Breeding, Pregnancy, and Parturition

Chapter 20 BREEDING, PREGNANCY, AND PARTURITION





SEXUAL BEHAVIOR


Breeding management of both the bitch and the stud involves a good deal of emphasis on normal “instincts” or normal “behavior.” There is little doubt, however, that humans influence dogs and their behavior patterns. It can be difficult to understand and assess the effect of the interaction between owner influence and a variety of other environmental factors on pet dogs that do have strong instinctive behavior patterns.





Changes in Sexual Behavior in Proestrus and Estrus


In response to increases in plasma estrogen concentrations, the bitch is frequently observed to be more interested in interacting with other dogs, to be restless or nervous, to have an increase or decrease in appetite, to drink more, and/or to urinate more frequently (Farstad, 1998). The increase in urination may aid in dispersing pheromones present in the urine and vaginal secretions that attract male dogs. This pheromone has the chemical structure of methyl-hydroxybenzoate.


Using a scoring system to assess changes in the behavior of the bitch and the stud, an objective view of changing patterns can be appreciated (Tables 20-1 and 20-2) (Concannon et al, 1979). The female changes from being outwardly hostile to the male, to becoming passive but resistant, and finally to being actively receptive. Obviously, the key behavioral change during this series of events is the female becoming overtly receptive to males. The bitch in estrus stands still when approached by a male and deviates her tail to one side (“flagging”). Some females may present their vulva by elevating it when sniffed by a male. Often contractions may be observed in the perineal and rectal muscles. The bitch may assume a “lordosis” posture if a male places a paw on her back. If the male is timid, she may back up to him, poke him in the side with her nose, paw on his back, or even mount him. As estrus progresses, the female may become less interested in mating. The behavior at the end of estrus is not marked by an abrupt alteration (Farstad, 1998).




Bitches tend to show a gradual decline in acceptance of males over 1 to 4 days. Behavior is definitely variable in late estrus and early diestrus when correlated with vaginal cytology. The female response to an aggressive or persistent male when she is in late estrus may be initial reluctance followed by acceptance of copulation. It should be pointed out that males, too, may show a relative or absolute lack of interest in bitches that have progressed to early diestrus.




The Tie


Courtship behavior, as previously described, usually precedes copulation. Courtship may be prolonged by play or chasing activity, or it may consist of the male briefly licking the vulva prior to mounting. Any attempt at mounting by the male typically causes the bitch to stand firmly in place. Mounting (stage 1 of normal mating) consists of the male clasping the flanks of the female, with his forelegs anterior to the hip joints. Intromission appears to be achieved through tentative trial and error pelvic thrusting of the penis toward the vaginal opening (stage 2 of normal mating).


Intromission (stage 2 of mating; stage 1 of coitus; Fig. 20-1) can be accomplished without the male having an erection because the os penis provides rigidity. If the male had an erection prior to intromission, the enlarged bulbus glandis would actually prevent intromission. With normal breeding, intromission takes place, erection then begins (stage 3 of mating), and “stepping” movements of the male’s rear legs are seen. Engorgement of the bulbus glandis takes place simultaneously with the stepping movements. The pelvic thrusting becomes more aggressive, and ejaculation of sperm-free prostatic fluid takes place during the initial 15 to 60 seconds of intromission.



After pelvic thrusting, the male typically dismounts (stage 4; see Fig. 20-1) by placing both front legs to one side of the bitch, lifting one hind leg over her back, and standing tail to tail with her (stage 4; see Fig. 20-1). Full engorgement of the bulbus glandis makes withdrawal of the penis from the relatively small vaginal opening impossible. Thus the male and female are locked, or “tied,” together (Fig. 20-2). This is described as an inside tie. If the male’s erection precedes intromission, the relatively large bulbus glandis cannot enter the vagina, and the result is an outside tie. Dogs that have achieved an inside tie (normal mating) usually remain “locked” together for 5 to 60 minutes. They may actually drag each other around during this period. During the first 1 to 5 minutes of a tie, the male is ejaculating sperm-rich semen. The ejaculate throughout the remainder of a tie consists of sperm-free prostatic fluid.




Factors Affecting Sexual Behavior







ARTIFICIAL INSEMINATION (AI): GENERAL INFORMATION



Indications for Artificial Insemination


There are numerous reasons for an owner to choose AI over natural breeding, but the primary explanations are that the male and female live some distance from each other or there is a perceived inability for the male and female to breed. This inability may be the result of the presence of a vaginal stricture, which impedes intromission by the male and causes pain during breeding for the female (see Chapter 25). Additional reasons for failure to breed include orthopedic problems, such as disk disease, stifle problems, or muscle weakness.


AI may also be chosen because of a major size difference between the mates. Either the male or female may be inexperienced, or one dog may have a history of refusing to mate or to allow mating by the other. If the male or female has a history of attacking the other, the owner may simply want to avoid confrontation. Some bitches appear never to enter standing heat, refusing all breeding attempts by any male.


Less commonly, some owners wish to avoid venereal diseases resulting from contact between their dog and its mate. This seems uncalled for when working with Brucella-free animals. Any agent that could be transmitted from stud to bitch during natural mating is not avoided with AI. However, AI avoids transmission of any agent from the bitch to the stud. Some male dogs (particularly Doberman Pinschers) experience some prostatic bleeding after exposure to a bitch in heat (see Chapter 30). This may be associated with von Willebrand’s disease. In this situation, AI can be performed without any contact between stud and bitch, occasionally avoiding this problem.


Fresh extended and frozen forms of semen are being used with increasing frequency. Obviously, shipped semen must be artificially inseminated into a bitch. Because semen collection is the “rate-limiting” factor in AI, insemination of extended or previously frozen semen remains a relatively simple procedure (Fontbonne et al, 2000).



Success Rates for Artificial Insemination


AI may be associated with lower conception rates and smaller litter sizes than would be achieved with natural breeding (Andersen, 1980). This is likely a result of several factors. During natural breeding, semen is pressure forced through the cervix into the uterus and oviducts (see Fig. 20-2), whereas in AI, the semen is placed posterior to the cervix. With natural breeding, uterine contractions aid in semen transport. This is an unlikely event in most AI situations. Also in natural breeding, the duration of the tie may contribute to improving conception rates.


A review of various reports shows that conception rates are less with every method of artificial insemination compared with natural breeding. Natural breeding has been reported to be associated with pregnancies at a rate of 80% to 100%; with fresh semen and artificial insemination, the rate is 62% to 100%; with chilled extended semen and intravaginal insemination, the rate is 60% to 80%; and with frozen semen and intravaginal insemination, the rate is 52% to 60% (Kustritz and Johnston, 2000b). Litter size also appears to be smaller with any insemination method compared with natural breeding (Linde-Forsberg and Forsberg, 1989, 1993; Fontbonne and Badinand, 1993; Silva, 1996).


It is our opinion that the above percentages, if incorrect, underestimate the success rates associated with each method of achieving conception. Experience and expertise have dramatically improved during the past decade, and each methodology has true attributes. There is little doubt that natural breeding, for numerous reasons, achieves the greatest conception rates. However, in various situations, natural breeding is not an option, therefore the various alternatives have potential to offer success. Nevertheless, we do not underestimate the value of experience with respect to relating conception rates to any “artificial” protocol.



ARTIFICIAL INSEMINATION (AI): INTRAVAGINAL TECHNIQUE



Collection of Semen






PROTOCOL.

With the owner holding the stud, to provide him with someone familiar and to protect the collector from being bitten, the penis and bulbus glandis are gently massaged within the penile sheath. When the bulbus glandis begins to enlarge, the sheath is slipped posteriorly, and the penis, including the bulbus glandis, is exteriorized. Failure to exteriorize the penis and the bulbus glandis from the sheath usually results in an incomplete erection and failure to ejaculate, presumably due to pain.


Once the penis and bulbus glandis are extruded from the sheath, the collector firmly holds onto the base of the penis, proximal to the bulbus glandis. The thumb and index finger are used, providing both massaging movements and downward pressure around the base of the bulbus glandis (Fig. 20-4). During or immediately after achieving an erection, aggressive pelvic thrusting movements by the stud, which accompany the onset of ejaculation, may make it difficult to place the artificial vagina over the penis. However, the pelvic thrusting is typically short-lived (5 to 15 seconds) and, as previously described, the initial 5 to 30 seconds of ejaculate consists of sperm-free prostatic fluid. There is no need to collect this sperm-free fluid; therefore there should be no alarm if pelvic thrusting interferes with collection of the initial fluid of the ejaculate.



The sperm-rich second fraction of the ejaculate usually begins as the pelvic thrusting stops. At the same time, moreover, many males step over the collector’s arm, as if dismounting the bitch. The collector should simply allow this instinctive movement by the male and bring the penis between the rear legs of the stud for continued collection (Fig. 20-4, B). Semen is usually collected for 2 to 5 minutes. The clear plastic tube should already have been connected to the rubber artificial vagina, and the apparatus can be held under the collector’s arm during the initial stimulation period to provide some warmth. Canine semen is relatively resistant to cold shock, alleviating the need for warm water tanks or incubators for holding semen.


Use of a clear plastic collection tube allows visualization of the semen. We usually collect semen for approximately 2 to 4 minutes, keeping one hand over the plastic to avoid excessive exposure to light. As long as the ejaculate is obviously whitish or cloudy (normal and sperm rich), it continues to be collected. Whenever the ejaculate becomes clear (sperm free), collection can be discontinued. If the collector is not certain whether the male has stopped ejaculating the sperm-rich fraction, collection should be stopped after 3 to 4 minutes (Farstad, 1998). Continued collection only dilutes the sperm with the phase 3 clear, sperm-free prostatic fluid, resulting in cumbersome fluid volumes. Alternatively, the collection system containing sperm-rich semen can be exchanged for a clean system if there is any need to evaluate the prostatic fluid.


The most difficult task in AI is collection of semen from the male. Once this has been accomplished, the balance of the procedure is quite simple. The bitch should be inseminated within 10 to 15 minutes of collection of semen from the male. If the semen appears grossly normal, we inseminate the bitch immediately after collecting the semen, saving several drops for postinsemination microscopic evaluation. If there are any questions about the male or if the ejaculate is abnormal in color or consistency, it is evaluated prior to insemination. During any delay, the collector keeps the semen warm by holding the tube in the hand, which also keeps the semen out of potentially harmful ultraviolet rays.



Insemination Procedure


The male is taken out of the room to avoid any distractions. Wearing sterile gloves, the inseminator draws the semen into a sterile, new, 6 ml syringe. Every attempt should be made to stop semen collection as soon as sperm-free prostatic fluid is seen so as to avoid an excessive volume. The smaller the volume (less than 4 to 6 ml is excellent), the less leakage of semen from the vaginal vault of the bitch after AI. Once the semen is in the syringe with at least 1 to 2 ml of air, a new clean urethral catheter is attached (see Fig. 20-3). The owner is usually given the job of holding the bitch’s head and keeping the bitch’s tail to one side.


A gloved, nonlubricated index finger (except in very small dogs, in which case the little finger is used) is inserted into the vaginal vault, palm up. If lubricant is used, it must be nonspermicidal. Lubricant is often not needed, or only a tiny amount is necessary due to the normal vaginal discharge associated with estrus. The urethral catheter is then slid over the top of the finger and passed into the vaginal vault until resistance is met. Because of the unique anatomy of the canine cervix (Fig. 20-5), it is difficult at best to pass a catheter through the cervix and into the uterus (Roszel, 1992). Therefore the goal should be to pass the urethral catheter cranial to the “cervical os.” Realistically, the inseminator passes the catheter as far cranially as possible, having first estimated the length of the catheter against the distance from the vulva to the cranial edge of the pelvic floor. The index finger aids in avoiding both the clitoral fossa and the urethra. The catheter follows the dorsal curvature of the vaginal vault. Semen is flushed into the vaginal vault and cleared with the air that was also in the syringe. Once this procedure has been completed, the catheter is removed.



The index finger can be used to stroke the roof of the vaginal vault or the clitoris, which sometimes causes obvious vaginal (uterine?) contractions. Once contractions have stopped, the index finger is withdrawn and the rear legs are raised so that the bitch is held in a “wheelbarrow” fashion. This helps the semen flow through the cervix. Usually we have the owners sit in a comfortable chair with a drape over their lap and have them hold the rear legs of the bitch up for at least 10 to 15 minutes. During this time the remaining semen is examined microscopically by the collector. The entire insemination procedure is rarely a problem for the bitch. There should not be any pain or discomfort associated with the procedure, making it rather simple and not time-consuming.




ARTIFICIAL INSEMINATION (AI): TRANSCERVICAL INSEMINATION (TCI)



Background





ANATOMY.

Familiarity with canine anatomy is required to become competent with TCI. The vagina of the bitch is relatively long compared with other species. The total length of the vagina in the typical 11 kg female has been estimated to be 10 to 14 cm, and for large breed dogs it can be as long as 30 cm (Pineda et al, 1973). Visualization of the cervix is normally compromised by the dorsal median fold (Fig. 20-6), which extends caudally 2 to 4 cm from the cervix. The paracervix is the term used to identify this portion of the cranial vaginal vault (Lindsay, 1983). The caudal portion of the paracervix ends in a narrow “tubercle,” which has the appearance of a cervix when viewed from the rear; this explains why some individuals incorrectly assume that they can routinely visualize the cervix with various scopes. Cranially, the paracervix ends in a fornix. The fornix is a slitlike space cranioventral to the true cervix and is a blind pouch (see Figs. 20-5 and 20-6).



The cervix lies diagonally across the uterovaginal junction and is directed craniodorsally, connecting the vagina with the uterus. Thus the external opening of the cervix faces the floor of the vagina and is located in the center of a rosette of furrows in most bitches. This angle, plus the small diameter of the cervical canal, creates natural obstacles to an attempt to pass a catheter from the vagina into the uterus (Wilson, 2001). Maiden bitches present a greater challenge because their cervical lumen is, on average, narrowest.



“New Zealand” Endoscopic Technique





EQUIPMENT.

The equipment used is a rigid, extended length cystourethroscope (Storz, Coleta, CA). This tool has a telescope with a 30-degree oblique viewing angle, a sheath, a bridge, and a cold light source. The working length of the assembled endoscope is 29 cm (Fig. 20-7). This tool can be used with virtually any breed, regardless of size. A nonessential video camera can be attached. Finally, the actual insemination is accomplished with a 6 or 8 French urinary catheter (the 6 French size is sometimes needed for small or maiden bitches). The best technique for this procedure also uses a specially designed hydraulic platform table that provides a tie point to the dog’s collar and an abdominal band that prevents sitting or any sideways movement. The table can be placed at a level that gives the operator optimum positioning during the procedure (Fig. 20-8).





PROCEDURE.

The endoscope is placed into the vagina and visually advanced through the vaginal folds. When a bitch is in proestrus or early estrus, the rounded vaginal folds (see Chapter 19) that tend to fill the vaginal lumen can impede placement of the endoscope. Dehydration of these folds, associated with continuing estrus, allows better visualization. The caudal tubercle of the dorsal median fold (DMF) is a prominent landmark (see Fig. 20-6). The lumen may be quite narrow in this region, sometimes requiring manipulation of the endoscope to the widest space and occasionally causing the endoscope to be pushed lateral to the DMF rather than being maintained in the more ideal midline. The vaginal cervix may not be obvious because it faces caudoventrally or ventrally. To locate the cervical os, the operator usually must advance the scope under the cervical tubercle. The os can be identified as being centered in the rosette of furrows or by observing the flow of serosanguineous uterine fluid through the cervix. The positioning of the os may appear to change during estrus as dehydration of vaginal folds progresses.


Most bitches in estrus tolerate transcervical insemination without anesthesia or sedation. The catheter should be advanced into the cervical os by careful manipulation of the endoscope and catheter. The rigidity of the endoscope allows the operator to move the cervical tubercle, line up the os, and change the canal angle. Air insufflation is not needed to visualize vaginal structures. Once the catheter tip has been introduced into the os, it can be steadily advanced with a twirling movement to aid passage through the cervical canal. The catheter is then advanced as far as possible, without force, for semen deposition. To ensure correct placement, it is important that the operator observe semen flow through the catheter and see no back flow. If back flow of semen does occur, the operator should stop the insemination and reposition the catheter, either inserting it farther in or withdrawing it slightly.


In some bitches, the amount of space in the paracervix is too small to accommodate the endoscope. This problem may be encountered in some small breed dogs and with some maiden bitches. Endoscopes with a smaller diameter may be used, although such scopes have a shorter length. The shorter length limits use of these scopes to small breeds. The longer scope may be difficult to manipulate in small breeds, sometimes requiring their sedation. Even when the scope can be positioned without difficulty, some bitches are not easily catheterized due to unusual anatomy, poor visibility secondary to vaginal discharges, or lack of cooperation.





FERTILIZATION



The Egg


Understanding the temporal relationships between ovulation, fertilization, and breeding behavior of the bitch may aid in caring for dogs used in breeding programs, specifically dogs suspected of being infertile. In an “average” bitch, there is a consistent sequence of events leading to pregnancy as she progresses through proestrus and into estrus (standing heat). The luteinizing hormone (LH) peak occurs on the second day of standing heat (Concannon and Yeager, 1990). Twenty-four to 96 hours later, averaging the fourth day of standing heat, ovulation begins. Studies indicate that it takes 72 hours for approximately 75% of the follicles to rupture and 96 hours after the LH surge for more than 90% of the follicles to rupture (Wildt et al, 1978). The eggs released are “primary” oocytes that must undergo two meiotic divisions, requiring 48 to 72 hours, before they can be fertilized. Once mature, the fertile life of “secondary” oocytes may be as brief as 24 to 72 hours (Phemister et al, 1973). Fertilization, therefore, on average, takes place on day 7 of estrus (standing heat).


Eggs are fertilized in the average bitch from the middle of the fifth day of standing heat through the ninth day after the beginning of standing heat. Minimal fertility may persist for 1 or 2 days after the beginning of diestrus, as determined by vaginal cytology (Fig. 20-9). However, because most bitches are not precisely “average,” predicting a precise day of fertilization is difficult (Concannon et al, 1989b), therefore no single day is optimal for a stud to breed the normal bitch. Conception usually occurs, however, with a single natural breeding (Figs. 20-9 and 20-10). When 21 bitches were bred twice, once 36 hours prior to ovulation and once 84 hours after ovulation, each time to a different male, only two of the bitches conceived pups from only the second male (Doak et al, 1967). This suggests that some advantage is gained by breeding early in estrus. The primary goal in breeding should be to obtain at least one mating every 2 to4 days during standing heat. Embryonic cleavage between 2 and 16 cells occurs more rapidly after fertilization of more mature versus less mature oocytes, explaining in part why gestation length is similar whether mating occurs before or after ovulation (Bysted et al, 2000; Concannon et al, 2000).




The Sperm


Knowing the potential life span of canine sperm in the uterus of the bitch is also helpful in understanding breeding management and conception. Sperm from a natural mating may reach the oviduct of the bitch within 25 seconds of ejaculation. More important, canine sperm has a relatively long survival period in the uterus. Undiminished concentrations of motile sperm have been found in the uterus 4 to 6 days after a single breeding. Breeding trials have suggested that canine sperm has a fertile intrauterine life span of 6 to 7 days after breeding (Doak et al, 1967; Concannon et al, 1983). Also, motile sperm have been observed in bitches as late as 11 days after a single mating. Sperm requires 7 hours of capacitation in the uterus. Once this time period has passed, sperm can penetrate the zona pellucida. In vitro, sperm can enter the vitellus and undergo nuclear decondensation in immature (primary) oocytes (Mahi-Brown et al, 1982).


The length of time that fertile eggs (primary and secondary oocytes) remain in the oviducts (several days), coupled with the longevity of sperm capable of fertilization after a single mating, suggests that a single breeding is quite likely to result in conception (see Figs. 20-9 and 20-10). Single matings per bitch per cycle, beginning 2 days prior to the LH surge through 5 days after, have resulted in conception in 95% of healthy bitches. Maximum litter sizes have been observed among bitches bred once 4 to 10 days before the onset of diestrus. Conception rates fall to 80% if the single breeding takes place 6 days after the LH surge, and the percentage of successful conceptions continues to fall to virtually zero 10 days after the LH peak. Litter size also decreases. The average onset of diestrus was the eighth day after the LH surge. These various factors agree with the tentative scheme outlined in Fig. 20-9 and with the results of early research (see Fig. 20-10).




BREEDING MANAGEMENT OF THE BITCH




Age, Silent Heat, Split Heat, Inexperience, and Ovulation Failure









Breeding Intervals per Estrus and When Breeding Should Begin





CRITERION 1: BEHAVIOR.

Behavioral estrus (standing heat) is the factor in determining when breeding of the bitch should begin. In most bitches, estrus behavior is synonymous with fertility. Therefore observation of the bitch’s response to a male is an inexpensive and reliable means of determining when to begin and end breedings. Occasionally it is advisable to have both the male and the female leashed, with one handler for each, in case of fighting. However, if possible, it is better to allow the male and female some freedom of movement, and if the female stands for the male, breeding should begin regardless of the color of the vaginal discharge, the vaginal exfoliative cytology interpretation, or the “day of the cycle.”


On day 5 or 6 of proestrus, the bitch should be brought into contact with a male dog for approximately 10 to 20 minutes. This should be repeated every second or third day. Breeding should begin whenever the bitch is willing to breed (behavioral estrus) and should continue every other day (daily if AI is being used) until she is no longer willing to breed. The one variable that cannot be overstated is the inability to predict the number of days a bitch will be in estrus (will allow mating); the average is 7 to 9 days.


We recommend breeding the bitch every 2 to 4 days, beginning with the first day of acceptance and continuing throughout the acceptance period. If the period of standing heat for an individual bitch cannot be predicted, breeding every second or third day is an excellent routine. Based on observations from previous ovarian cycles in an individual bitch, an educated guess may be made regarding the duration of estrus, because a bitch 2 to 6 years of age tends to be similar from one cycle to the next. Bitches typically in standing heat for longer than 12 days should be bred every third or fourth day. Bitches typically in standing heat for only 3 or 4 days should be bred every 24 to 48 hours.


It is of paramount importance to recommend to owners that the male continue breeding the bitch until the bitch refuses to breed or until the first day of diestrus is documented with vaginal cytology. Fertilization of eggs is most likely occurring in the final 4 or 5 days of standing heat, regardless of the length of standing heat, or 4 to 5 days before the onset of diestrus.





CRITERION 4: SERUM PROGESTERONE CONCENTRATION.

In-hospital test kits for determining the serum progesterone concentration are widely available, and reference laboratories are providing rapid turnaround of submitted samples, making progesterone a useful tool for timing ovulation. It is recommended that serum be assessed beginning 3 or 4 days after a bloody vaginal discharge is observed or within 1 or 2 days of detection of greater than 60% superficial cells on vaginal cytology. Ideally, the first sample documents plasma progesterone concentrations less than 1 ng/ml. The bitch should then be assessed daily or every other day until a distinct rise of greater than 1 ng/ml is noted, which suggests that the LH surge is occurring or has occurred (Eckersall and Harvey, 1987; England et al, 1989; Hegstad and Johnston, 1992; Manothaiudom et al, 1995; Goodman, 2001). Breeding or AI should then begin and continue every other day (or daily with AI) for 8 days or until another criterion (vaginal cytology or behavior) demonstrates that breeding should be discontinued.


The serum progesterone level begins to rise concurrently with the LH surge, reaching 1.0 to 1.9 ng/ml (3.1 to 5.9 nmol/L) on the day the surge takes place. The day after the LH surge, 1 day before ovulation, the serum progesterone concentration is 2.0 to 3.9 ng/ml (6.2 to 12.1 nmol/L). On the day of ovulation, the serum progesterone concentration is 4.0 to 10.0 ng/ml (12.4 to 31.0 nmol/L). Several enzyme-linked immunosorbent assay (ELISA) kits for assessing the progesterone concentration are available for use in the veterinary hospital (i.e., PreMate, Camelot Farms, College Station, TX; Status-Pro, Synbiotics, Malvern, PA). Critical evaluation of these kits has demonstrated poor correlation with radioimmunoassay (RIA) systems, specifically in the 1.5 to 10.0 ng/ml range. This is the range of greatest importance for ovulation timing. Whenever possible, therefore, laboratory RIA testing should be used (Bouchard et al, 1993; Kustritz and Johnston, 2000a).

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Jul 10, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Breeding, Pregnancy, and Parturition
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