The Basics Of Canine Reproduction
The Estrous Cycle
- Starts as early as 6 months of age in smaller breeds
- As late as 24 months of age in larger breeds
- Lots of individual and breed variations
- Ideal age for breeding is between 2 and 6 years of age
- Cycle is usually every 6 months
Phases of the estrous cycle
a)Proestrus
- Period of heightened follicular activity preceeding estrus
- Typically see bloody vaginal discharge (duration of 7 to 10 days)
- Enlargement of vulva, attration of males to females, changes in behavior.
- Female in early proestrus discourages mounting; growling, snapping, etc. at male.
Duration:
b) Estrus
- Period when female allows male to mount and breed
- The first day the female allows breeding is the start of estrus (‘standing heat’)
- Estrus ends when female does not allow breeding
- Hormone status: increasing progesterone, decreasing estrogen
- Duration: 6 to 12 days
c) Diestrus
- Period following mating
- Refuses to accept mounting by male
- Duration: pregnant bitch ~ 56 to 58 days, non-pregnant ~ 60 to 80 days
- Formation of ‘CL’ (corpus lutea)
- Hormone status: dominated by progesterone
d) Anestrus
- Time period between diestrus (or whelping) and proestrus
- Uterus involution
- Not readily detectable in non-pregnant bitch
- Outward inactivity
Heat detection
- a. Vaginal cytology Reveals where bitch is in her cycle
By taking a swab of the lining of her vagina, the cells collected are stained and then viewed under a microscope
- b. serology
progesterone levels estimated using a blood sample
higher progesterone levels indicate estrus
- c. behavior
increasing receptivity to a male
passive & accepting of a male
may actively approach a male
**Note: some dogs experience a ‘silent heat’. These are heats that go unnoticed because there may be little swelling of the vulva, bleeding, attraction of males, or behavior change.
Breeding
A. Natural
- Record the first day of vulvar swelling, bloody vaginal discharge, and when males become interested in the bitch
- Begin ‘teasing’ the bitch with a male dog on day 5 or 6 of proestrus. Repeat this every 2 or 3 days to determine the first day of standing heat
- Allow the bitch to be bred, beginning on her first day of acceptance of the male, and continue to breed every 2 to 4 days throughout the acceptance period.
- i. The ‘Tie’
- Once the male has accomplished intromission an erection occurs. The bulbous glandis engorges making the withdrawal of the penis impossible. During this time (anywhere from 5 to 60 minutes) the male will dismount so he is tail to tail with the female. They may lay down or drag each other around. It is very important not to interfere during this time. Sometimes a male may achieve an erection before entering a female, so a tie is not formed.
- ii. Factors affecting sexual behavior
- Environment: male dogs more territorial than females
- If female is dominant breeding may not be successful
- Male dominance may be pronounced in own territory; bring female to male
- Experience: young adult males may be overexcited when around females in heat (may mount head, flank, etc.)
- Maiden females may show longer play behavior
B. Artificial insemination
- Indications: inability for male and female to breed
- Anatomical problems with female
- Skeletal/muscle problems
- Size difference
- Inexperienced dogs
- Aggression
- Others
- Collection of semen performed at clinic.
- Insemination procedure can be performed at our clinic.
- Surgical insemination can be performed. This procedure is performed at a referral clinic.
Success rates: generally see lower conception rate and smaller litter sizes
- Why? Natural breeding:
- Pressure forces semen through cervix into uterus and oviducts
- Causes uterine contractions which help transport semen
- Has the benefit of the tie
Pregnancy Diagnosis
- e. Palpation
The veterinarian can usually feel the fetuses at about 20 to 30 days gestation
May be harder to feel later on as the ‘pearl string’ shape of the pregnant uterus changes to a ‘sausage like’ shape resembling intestine
- f. Radiographs
Fetal skeletons may be seen on radiograph 20 days prior to whelping (or 45 days gestation)
- g. Ultrasound
Fetal vesicles can be seen by ultrasound at about 20 days gestation
Fetal heartbeats can be heard with the use of a ‘doppler’ unit as early as 25 days gestation
Other things to know
- Semen is capable of fertilization for at least 4 to 6 days
- Females can have ‘split heats’. These heats begin normally but she does not enter standing heat; diestrus begins instead, with proestrus starting 2 to 10 weeks later. Split heats can repeat several times.
- Despite what some breeders think, there are no significant differences in size, weight or maturity of puppies where breeding has occurred every 2 to 4 days during a heat. Differences in pups are likely related to the overall health of each pup, its placenta, the genetic background, and the health of the area of the uterus where the pup develops.
- Gestation length: 56 ~ 58 days
- Ovulation occurs through 24 ~ 96 hours after onset of estrus
- Eggs are fertile for 12 to 24 hours
- Pre-breeding health issues:
- i. Vaccinations should be current before the female enters proestrus
- ii. Brucellosis testing should be performed. This infection can cause abortions.
- iii. Deworm the bitch before breeding as some parasites cans transfer to the pups from the bitch
