This is an excerpt from Breeder’s Handbook on Canine Reproduction from Royal Canin. Providing accurate and useful information on the practicalities of reproduction in breeding kennels is a goal of Royal Canin.
Since 1967, Royal Canin has been at the forefront of developing innovative nutritional responses in the field of dog breeding. Even if nutrition is fundamental in breeding, it cannot give all the keys for success. Application of reproduction techniques is the deciding factor. The Handbook is an optimal collaboration with international authors who are specialized in reproduction and have a thorough understanding of the problems experienced by breeders.
Breeder's Handbook: Gestation 101
Stages of Gestation
Gestation begins from fertilization of the ovum by a spermatozoon, although a breeder can really only detect this much later, around 21 days. However, even though remaining invisible from the outside, early embryonic development and implantation are crucial phases for the future puppies.
advantages accurately monitoring estrus
If estrus is monitored by tests such as progesterone assays, the moment of ovulation can be determined fairly accurately. Breeders then very often find that whelping takes place exactly two months later. For example, a bitch mated on September 25—after careful monitoring of estrus and with ovulation on September 23—will most likely whelp on November 25.
fertilization and implantation
Fertilization, i.e., the union of a spermatozoon and an ovum, takes place very high up in the uterus, in the fallopian tubes. Toward the end of the first week that follows, the embryos migrate from the fallopian tubes toward the uterine horns. They then float and move around in the uterine fluid and can even switch from one horn to another (they can also have been conceived on the right-hand side of the uterus before implantation in the left horn).
Embryos then become immobile, facing toward a uterine gland. They implant themselves relatively tardily, toward the 16th day after ovulation—this is nidation or implantation. It is only after this stage that they actually begin to develop, along with their adnexa.
Two Distinct Phases
Development of the future puppy can be split into two phases:
• Embryogenesis, during which all future organs come into place. Among other significant events, one might mention the appearance of eyelids at 32 days, fusing of the palate at 33 days, and differentiation of toes at 35 days. For example, if the palate has not fused by the end of this phase—this is what is known as a cleft palate—this will not occur subsequently during gestation. At the end of the embryogenesis, future puppies are not very big, although most structures are in place and all organs have started to develop. At this stage, the embryo becomes a fetus and it is possible to recognize the species from observation.
• Weight gain: Over three-quarters of a puppy’s weight at birth is gained by the fetus after the 40th day of gestation.
Physiology of Gestation
Gestation is a complex process of exchange between the mother and her fetuses. The female must offer an appropriate hormonal uterine environment, while providing optimal nourishment for the future puppies through the placenta.
Gestation begins from the moment
that a spermatozoon penetrates
the ovum, after which the first cell
Gestation is controlled mainly by just one hormone—progesterone. In the bitch, it is the yellow endocrine bodies in the ovaries (corpora lutea) that secrete this hormone, unlike other species in which it may be secreted by the placenta.
Progesterone continues to be secreted for a further two months after estrus, whether or not the bitch is gestating. This has a number of consequences.
To start with, it is difficult to establish a diagnosis of pregnancy by assaying this hormone, since it is normally present even in non-pregnant bitches.
Next, a sharp drop in a pregnant bitch’s progesterone level—what veterinarians call luteal failure—may bring gestation to a halt.
The placenta is an area of close contact between the two organisms and a point of exchange between mother and puppies. In bitches, the blood supplies of mother and fetuses are not intimately mingled as in humans, but they are still very close which means that various chemical substances and pathogens can easily pass through.
The placenta forms a circular, ringlike band around the fetus (known as zonary placenta). It is pigmented dark green, almost black, and can be seen at the time of whelping when the placentas become detached.
The placenta secretes a hormone called relaxin which can be used to diagnose pregnancy (see below).
The placenta has many
as well as hormonal.
||Progesterone is the main hormone in gestation. The hormone
Relaxin can be used to diagnose pregnancy.
The puppy is surrounded by several sacs. To simplify things, it lies first in the amnion filled with amniotic fluid. This is the transparent sac that surrounds a newborn puppy at birth. The fluid helps to protect against knocks, as well as having a nutritive and detoxifying role.
The amnion itself is surrounded by another larger sac—the allantois. This is the well-known bag of water, which is punctured anytime from a couple of minutes to many minutes before birth.
Abnormalities in Fertilization
Abnormalities in fertilization cover the factors that can prevent sperm from reaching the ova. The bitch is still not pregnant just after mating, since gestation has not yet started. In the great majority of cases, failure to fertilize is due to poor calculation of the date for mating, but there may be other causes as well.
Appearance of vaginitis through an endoscope: left, granulomatous
vaginitis, characterized by small lumps visible on the
mucous membrane, right, normal mucous membrane.
This is an inflammation of the vagina that can occur frequently, although it is rarely diagnosed because the symptoms induced are fairly sparse. The bitch may have a moderate genital discharge, lick her vulva, and be attractive to males even though she is not in heat, or else suffer from repeated urinary infections. Nothing here really points to the cause.
Vaginitis, however, is a frequent cause of infertility in brood bitches and, because of this, they should be constantly screened and treated.
Diagnosis is difficult. Although examining the posterior area of the vagina using a speculum or taking vaginal smears can help (one often finds the presence of many white corpuscles or leucocytes), the best procedure consists of inserting a small endoscope into the vagina (vaginoscopy) to examine the exact state of this organ.
Local or general treatment with antibiotics needs to be long term, since these have difficulty in penetrating this organ.
Anatomical deformities of the vagina, such as stenosis or the presence of vaginal hyperplasia during estrus, will generally prevent mating taking place correctly—and this is often how they are detected.
Rarely, one can find nondevelopment of the deeper part of the vagina (uterine aplasia) or continued existence of the hymen. This might be suspected when a bitch has no discharge during estrus, because obviously the blood from the uterus cannot flow out.
deformities in the fallopian tubes and uterus
The uterus or fallopian tubes may no longer be permeable to sperm as a result of congenital malformation (segmentation of the genital system, growth defect, etc). In this case, a bitch will be sterile from the start.
However, other deformities can also appear. In the uterus, this is the case, for example, with traumatisms suffered during whelping or with the formation of uterine adhesions due to an incorrectly performed cesarean section. Ultrasound or radiological examinations may help in making a diagnosis.
Deformities in the fallopian tubes, whether congenital or resulting from infection, require a hystero-salpingography to be carried out in order to diagnose them correctly, i.e., injection of an opaque substance into the uterus followed by radiographs.
In practice, such onerous and complicated procedures are never used on bitches, and the cause of such cases of infertility often remains unexplained.
vaginitis and fertility disorders
Vaginitis in adult bitches is usually of bacterial origin, and several studies clearly point to a potential link between bacteria and fertility disorders.
In the vagina, bacteria can create an unfavorable environment that produces a spermicidal effect or reduces the motility (ciliostasis) of the sperm ejaculated by the male, thus rendering them incapable of working their way through the uterus.
Above all, vaginal infections increase the risk of microbes entering the uterus, especially during estrus when the cervix is open.
In the uterus, such bacteria of vaginal origin may create an unfavorable environment for embryonic development (hence the risk of resorption of immature embryos), infiltrate the uterine wall and disrupt implantation, or cause inflammation of the endometrium (endometritis) and infect the placenta (placentitis), which may lead to the interruption of gestation.
For more information on Royal Canin and its nutritional solution for breeding bitches from the first day of estrus to the 42nd day of pregnancy, visit www.royalcanin.us/akc.