detection of estrus and pregnancy when dogs

detection of estrus and pregnancy when dogs

Cells of the vaginal epithelium mature to keratinized squamous epithelium under the influence of estrogen. Because of the rise in estrogen throughout proestrus, with peak levels occurring just prior to the onset of standing the heat, the vaginal smear can be used as an indicator of the bitch's readiness for breeding.

The smear will not confirm the presence of ovulation, nor is it of prognostic value in normal bitches during anestrus.

The percentage of vaginal epithelial cell cornification is an index of estrogen secretion by the ovarian follicles. As cornification of vaginal epithelial cells proceeds, the cells become larger, with more angular borders. The nuclear-cytoplasmic ratio decreases until the nuclei reach a point where they no longer take up stain (coincident with the onset of estrus). The cells appear "anuclear" and are classified as "cornified" or "anuclear squares." Cornification occurs approximately 2 days prior to the estrogen peak and 4 days prior to stand the heat. The percentage of cornified cells (of the total number of epithelial cells) decreases gradually to zero after the onset of diestrus. The vaginal cytology smear of the bitch changes from predominantly cornified to noncornified 6 days after ovulation. The day of this change is the first day of diestrus. Other epithelial cell types noted on vaginal cytology include superficial cells (large, angular cells with small nuclei); intermediate cells (round or oval cells with abundant cytoplasm and large, vesicular nuclei); and parabasal cells (small round or elongated cells with large, well-stained nuclei, and a high nuclear-cytoplasmic ratio). Based on vaginal cytology, the estrous cycle is classified as follows: Proestrus, early: intermediate and superficial cells, red blood cells, and neutrophils.
Proestrus, late: superficial cells, anuclear squames, and red blood cells.

Estrus: more than 50% anuclear squames, superficial cells, with or without red blood cells.
Diestrus: more than 50% intermediate cells, superficial cells and squames early, but becoming completely non-cornified with neutrophils present as diestrus proceeds.

Anestrus: small numbers of parabasal cells and intermediate cells, with or without neutrophils.

Although vaginal cytology is a useful tool, it is not a substitute for observation of behavioral estrus, which is the best criterion to use in breeding management. during proestrus, the male is attracted to the bitch and will investigate her hindquarters, but she will not accept breeding. The behavioral hallmark of estrus is standing receptivity toward the male. 

during this stage, the bitch will exhibit "flagging," or elevation of her tail with a muscular elevation of the vulva to facilitate penetration by the male. In order to maximize the conception rate, and the
a number of pups whelped per egg ovulated, it is recommended to breed the bitch on days 1, 3, and 5 of the standing heat.

-. Pregnancy
Fertilization is completed in the mid- to the distal oviduct. Implantation is evident by areas of local endometrial edema 17-18 days after breeding. There is no correlation between the number of corpora lutea and the number of fetuses in the corresponding uterine horn, suggesting transuterine migration of embryos.

The dog has endotheliochorial placentation. The endothelium of uterine vessels lies adjacent to the fetal chorion, mesenchymal, and endothelial tissues so that maternal and fetal blood are separated by four layers. The canine placenta is also classified as zonary and deciduate, indicating that the placental villi are arranged in a belt and that maternal decidual cells are shed with fetal placentas at parturition. The length of gestation is 59-63 days. Luteal progesterone is responsible for maintaining pregnancy, and canine corpora lutea retain their structural development throughout gestation. Serum progesterone rises from less than 1 ng/ml in late proestrus to a peak of 30-60 ng/ml during gestation then declines to 4-5 ng/ml just prior to parturition.

Progesterone is essential for endometrial gland growth, secretion of uterine milk, attachment of the placentas, and inhibition of uterine motility.

Pregnancy detection can be performed by abdominal palpation of the uterus 28 days after breeding. The embryos and chorioallantoic vesicles form a series of ovoid swellings in the early 
gravid uterus.
 They are approximately 2 inches in length at 28-30 days, the time at which pregnancy is most easily and accurately diagnosed. By day 35 the uterus begins to enlarge diffusely so that the vesicles (and, therefore, pregnancy) are difficult to identify by palpation. Fetal skeletons become calcified and are radiographically evident by day 42. Bitches in which a difficult whelping is anticipated should be radiographed in late pregnancy to determine the litter size and to evaluate the size of the fetal skulls in relation to the bony maternal birth canal. Real-time ultrasound can be utilized for pregnancy detection of vesicles as early as 25-28 days.

-. Parturition and the Neonate
An abrupt drop in body temperature to less than 100~ indicates impending parturition within 18-24 hours. The process of parturition has been divided into three stages, Stage 1 of labor lasts 6-12 hours and is characterized by uterine contractions and cervical dilation. During this stage, the bitch may appear restless, nervous, and anorexia. Other common clinical signs include hard panting and increased pulse and respiration rates.
Fetal expulsion occurs during stage 2, which lasts approximately 3-6 hours. As the fetus engages the cervix, the neuroendocrine system induces the release of oxytocin; this is referred to as the Ferguson reflex. 
Oxytocin strengthens the uterine contractions and may elicit voluntary abdominal contractions as well. The bitch is usually recumbent during stage 2 but is able to inhibit this stage if labor if disturbed. The chorioallantois ruptures either during the passage of each neonate through the birth canal or by the bitch's teeth at birth. Interestingly, the posterior presentation is common in dogs but does not predispose to dystocia.
 The time interval between delivery of each pup is irregular, but the average time lapse is less than 1 hour between pups until parturition is complete. Veterinary assistance is necessary if the bitch remains in stage 2 for more than 5 hours without delivering the first pup, or for more than 2 hours before delivering subsequent pups.
The placentas are expelled during stage 3 of labor, immediately following delivery of a pup or up to 15 minutes thereafter.
If two pups are delivered from alternate uterine horns, then the birth of both puppies may precede expulsion of the respective placentas. 
The bitch will lick the newborn vigorously to remove the membranes from its head and to promote respiration. She will also sever the umbilical cord. The bitch may ingest the placentas, although they confer no known nutritional benefit and may induce transient diarrhea.
Thermal support should be provided prior to parturition.
Dogs housed on grated flooring should be provided with mats, and those on solid floors would benefit from blankets placed in a corner of the primary enclosure. Shavings are discouraged as they have the potential to coat the umbilical cord, which may predispose to ascending infections. Heat lamps may be placed 24 hours prior to parturition and remain until all neonates demonstrate vigorous and successful suckling behavior. However, the use of heat lamps necessitates strict supervision in order to prevent thermal burns. If possible, whelping bitches should be housed in a quiet corridor in order to decrease periparturient stress, especially in primiparous or young mothers. Thus, monitoring of parturition is important, but human intervention should be minimal in order to prevent stress-induced cannibalism. Weak or debilitated puppies may be cannibalized by the bitch before the research staff recognizes the need for veterinary attention.
The postpartum use of oxytocin is required only in the event of uterine inertia, stillbirths, or agalactia. In these cases, 5-20 units of oxytocin may be administered intramuscularly. Uterine involution occurs during anestrus within 4-5 weeks of parturition. During this time a greenish to red-brown vaginal discharge, or lochia, may be noted. Although lochia is normal, the presence of an odiferous, purulent discharge, accompanied by systemic signs of illness, indicates metritis or pyometra.
Desquamation of the endometrium begins by the sixth postpartum week, with complete repair by 3 months.
Newborn puppies are easily sexed by examination of the anogenital distance. In female puppies, the vulva is evident a short distance from the anus, whereas the prepuce of male puppies is nearly adjacent to the umbilicus. Eyes are open at approximately 12 days, and ears are patent at approximately 12- 20 days. Solid food can be introduced between 4.5 and 6 weeks of age, and puppies can be weaned at 6-8 weeks.
-. Artificial insemination
there are vaginal abnormalities such as strictures, or when the bitch refuses to stand for breeding. Semen for AI is collected using a plastic centrifuge tube and rubber latex artificial vagina.
The male is introduced to the bitch's scent and manually stimulated. After collection of the first two fractions, a sufficient amount of the third fraction, which consists predominantly of prostatic fluid, is collected to bring the total semen volume to 4-6 ml. The semen is then drawn into a sterile 10 or 12 ml a syringe attached to a sterile disposable insemination pipette.
The bitch has inseminated either standing or with raised hindquarters. A gloved index finger is inserted into the dorsal commissure of the vulva and directed craniodorsally until it is over the ischial arch. The tip of the insemination pipette is introduced and guided by the gloved finger toward the external cervical os. The semen is injected, and 2-3 ml of air are then flushed through the syringe and pipette. The pipette is withdrawn, and the gloved finger is used to feather the ceiling of the vagina until contractions of the vaginal musculature are palpable. The bitch's hindquarters are subsequently elevated to promote pooling of semen around the external cervical os.
As with natural breeding, AI should be performed on days 1.3, and 5 of standing the heat, or on the days of maximal vaginal cornification. The bitch should be palpated for pregnancy approximately 4 weeks after the first insemination.
-. False Pregnancy
False pregnancy (pseudocyesis), a stage of mammary gland development and lactation associated with nesting or mothering
behavior, is common in the bitch. The condition occurs after the decline in serum progesterone toward the end of diestrus. 
There is no age or breed predisposition. Pseudopregnancy does not predispose the bitch to reproductive disease or infertility.
However, in the event of extreme discomfort due to mammary gland enlargement, bitches may be treated with mibolerone (Cheque Drops) at an oral dose of 16 ~tg/kg q24 hr for 3-5 days (Brown, 1984).
-. Reproductive Life Span
Reproductive performance in the bitch is optimal prior to 4 years of age. Although normal cycle lengths are reported to occur up to the ages of 5-7 years, the interestrous interval tends to increase by 4 years of age. Cycling does not completely cease; however, after 8 years of age, bitches demonstrate significant decreases in conception rate and a number of live pups whelped. By 8-9 years of age, pathologic conditions of the uterus, such as cysts, hyperplasia, atrophy, and neoplasia are extremely common.
D. Behavior Beagles have been a popular animal model because of their docile nature. They are easily handled and for the most part respond favorably to repetitive manipulations such as body weight measurements, physical examination, electrocardiogram (ECG) recordings, oral gavage, and venipuncture.
Dogs are sexually mature by 6-9 months of age, but they are not socially mature until 18-36 months of age. The socialization process should begin early during development when puppies are receptive to conspecific and human contact. For example, from 3-8 weeks of age, puppies are most capable of
learning about how to interact with other dogs. Between weeks 5 and 12, puppies are most capable of learning how to interact with people. By 10-12 weeks of age dogs voluntarily wander and explore new environments. 
Thus, early handling and mild stress (such as vaccination) appear to be extremely beneficial components of a dog's social exposure.
The extent to which breed affects behavior has been the subject of popular speculation but is difficult to prove. In general, breed-specific patterns do tend to emerge. For example, it appears that beagle pups are very motivated by food reward (Overall, 1997). 
This is not surprising, because the breed was selected to work with its nose, and this may be a useful attribute for laboratory investigations that are predicated on food restriction.
Canid social systems use signals and displays that minimize the probability of outright aggression. These behavior patterns are most likely elicited during distressful situations, such as strange environments, being handled by strange people, or encountering new animals. 

Related Posts
Disqus Comments