Canine parturition is a physiological process in which the fetus and its appendages are expelled from the uterus by the female dog when the normal gestation period of the dog is completed and the fetus is mature. Labor is a spontaneous physiological activity after the fetus has matured, and the factors that cause labor initiation are multifaceted, and are caused by the interconnection and coordination of many factors such as mechanical dilation, hormones, nerves and the fetus. The power of labor in female dogs relies mainly on the force generated by the rhythmic co-contraction of the smooth muscles of the uterus and the abdominal muscles to complete labor. 1. Contractions are the main driving force of labor. A rhythmic contraction of the smooth muscle of the uterus during labor is called a contraction. The contraction is due to the contraction of the uterine muscle under the action of oxytocin in the blood during labor. When the smooth muscle of the uterus contracts, the blood vessels are compressed and the blood circulation and oxygen supply are impaired. When the contraction of the smooth muscle of the uterus stops, the compression of the blood vessels is lifted and normal blood circulation and oxygen supply are restored, and this cycle produces contractions. This is very important for the safety of the fetus because prolonged contractions can prevent the blood supply to the placenta and cause the fetus to die from lack of oxygen. At the same time, there is a certain time interval between each two contractions, which is good for the female dog to recover her strength. 2. Nux vomica It is the auxiliary power of delivery. The contraction of the abdominal wall muscles and diaphragm is called nuchal, which is a random contraction that accompanies the contraction and plays an important role in the output of the fetus. Fetal position and direction of delivery
The fetal position is the relationship between the longitudinal axis of the fetal body and the longitudinal axis of the uterus, the longitudinal position is parallel to each other and the oblique position is crossed. The fetal position is caudal if the head of the fetus is toward the head of the female (or the tail of the fetus is toward the birth canal) and cephalic if the head of the fetus is toward the rear of the female (or the head of the fetus is toward the rear of the birth canal). There is no regularity in the fetal position of dogs and there is no relationship between the sex of the fetus. The fetal position and direction near the time of delivery is one of the factors that affect normal delivery.
Fetal orientation is the direction of the fetus’ back to the mother’s abdominal back. A fetus with its back facing the ventral side of the bitch is called an upper fetal orientation, one facing the dorsal side of the bitch is called a lower fetal orientation, and one facing the transverse abdomen of the bitch is called a lateral fetal orientation. Dogs, like pigs, are multiparous animals, and the left and right uterine horns of pregnancy are long and curved, even reversed, so the fetal direction cannot be completely determined.
Position of delivery.
Female dogs generally give birth in a side-lying position and occasionally in a defecating position. This is because when a female dog lies on her side, the fetus can easily enter the pelvic cavity, and the abdominal wall does not have to bear the weight of the internal organs and the fetus, making the abdominal muscle contraction stronger. In addition, lateral recumbency allows the two hind limbs to be straightened backwards, prompting the pelvic ligaments and attached muscles to fully relax, thus allowing the pelvic cavity to fully expand and facilitating the passage of the fetus. Therefore, the female dog usually shows the birthing position of lying on her side and straightening her hind limbs.
Delivery process.
The whole birthing period starts from the opening of the cervix and the beginning of uterine contractions to the expulsion of the fetal clothes. It is generally divided into three stages.
1. First stage (opening period)
From the beginning of the uterus contractions until the cervix is fully dilated. The duration of this phase varies widely, generally from 3 to 24 h. This phase is characterized by: generally only paroxysmal contractions, without nuchal accusations. Behavioral manifestations: slight restlessness and irritability; rising and lying down at times, walking back and forth; frequent urination movements, and sometimes a small amount of fecal and urinary discharge; accelerated respiration and pulse. Generally, the first-born dogs show obvious performance, while the female dogs in labor are relatively quiet.
2. Second stage (output period)
From when the cervix is fully dilated until all the fetuses are expelled. The duration of this stage depends on the condition of the female and the number of litters, and is usually within 6 h. If the number of litters is too large, it should not exceed 12 h. This stage is characterized by the co-occurrence and intensity of contractions and reproaches.
Behavioral manifestations: At this time, the female dog is extremely restless, with increased irritability and nuisance. When the first litter enters the pelvis, the contractions and nudges become more intense and last longer and are more frequent. At the same time, the female often extends her hind limbs outward, and after several strong strokes, she rests for a while and continues stroking until the fetus is expelled.
When the female finds the fetus wrapped in membranes at the pubic door, she will use her teeth to tear the membranes and expose the fetus. The tearing of the membranes lubricates the birth canal and allows the fetus to be expelled. After the fetus is delivered, the female will pull out and eat the membranes and placenta, bite off the umbilical cord of the fetus, and lick the entire body of the litter, especially licking away the sticky amniotic fluid from the nose and mouth of the litter to ensure that the litter can breathe and lick the entire coat dry. She will also lick her own vulva to clean it.
The second litter is usually delivered within 2 hours after the first litter is delivered. When the second litter is delivered and a contraction occurs, the female will temporarily leave the first litter behind to handle the birth of the second litter. This behavior is repeated until all litters are delivered. During the interval between litters, the female has the habit of standing up and walking around and panting. Once all litters are delivered, the female settles down to protect and care for her litter, licking her anus and its surroundings vigorously to stimulate the expulsion of the litter’s feces. The female does not concentrate on nursing during delivery, but will concentrate on nursing her litter after delivery is over.
Generally, females do not require human assistance during this period, and most females are averse to having people (including their owners) in their vicinity. However, first-time female dogs should be especially observed during this stage and assistance should be provided at all times.
3. Third stage (period of meconium expulsion)
From the time the fetus is expelled to the time when the meconium is completely expelled.
This stage is characterized by slight paroxysms with occasional slight nubs. The placenta and membranes are usually expelled within 15 min after each litter is delivered, and some may be expelled together with the next litter when it is delivered. The placenta is rich in protein and the female dog usually eats the placenta and membranes for energy and to facilitate delivery. At the same time, she licks the mucus that comes out of the vulva to clean the vagina. The female dog in this stage is quiet and in a state of fatigue. Note that the postpartum female dog has poor disease resistance and there is a possibility of injury during delivery, which can easily cause postpartum infection, so the female dog should be checked frequently after delivery.
