Dog and Cat Reproductive Cycles

• Reproduction and Normals in Dogs and Cats

Dog’s Life Span

• The maximum life span for a dog is estimated to be 27 years
• The average lifespan for a few animals is 16-18 years
• 10-14 years is considered normal for most dogs
  • Factors affecting life span include body size and breed
  • Small dogs live longer than larger dogs
  • St Bernard's life span is 4.1 years.
  • Irish wolfhound lifespan average of 6.2 years
  • Mixed-breed dogs live longer than purebred dogs
  • Neutered dogs live longer than unneutered
    • Reduced risk of diseases
    • Less likely to roam
  • Ultimately depends on the individual dog

Vital Statistics for a Healthy Dog and Cat

• Skin and coat
  • Normal characteristics include shine, growth, and shedding pattern typical for the breed
  • Pliable, clean skin, free of lesions
• Mucous membranes
  • Should be light pink in color (unpigmented areas)
  • Normal Capillary Refill Time (CRT) is 1 second
• Food intake and body weight: Normal and consistent appetite; maintenance of ideal (lean) body weight
• Body Temperature: 100.0-102.5 degrees Fahrenheit
• Pulse (resting)
  • In dogs, it's 60-140 bpm
  • For cats, it registers at 145-200 bpm
• Respiration
  • In dogs: 10-30 bpm
  • In cats: 20-14 BMP

Skin and Hair Coat

• The hair coat is a physical barrier between the external environment and the skin
• Some dogs only have hair over fur
• Fur grows to a pre-determined length and stops growing, hair continues to grow
  • All dogs and cats will shed their coat
  • Hair follicles in the skin are responsible for hair coat production
  • Each follicle is composed of a follicular sheath and a hair bulb
  • The follicular sheath is a tube-like structure through which hairs pass
  • The hair bulb is found in the base of the follicle
  • Dogs can have compound follicles containing Guard hair and fine secondary hairs
    • Guard hair is single, stiff, primary hair
    • Secondary hairs are thin and small hairs that make up the undercoat
  • Variations in the number and type of guard hairs and under hairs are seen between different breeds of dogs
  • The anagen phase is the hair's growth phase, lasting 6-8 weeks
    • Old hair sheds as new hair grows up the follicle
  • The telogen phase is the rest phase of hair
    • Variable and can be several weeks to several months
    • Depends on genetics, photoperiod, environmental temperature, age, breed, health, and reproductive status
    • Longer day lengths, like those in spring and summer, increase hair follicle activity
    • Short day length will result in a longer telogen phase
    • In spring/summer as daylight increases, shedding increases
    • Indoor pets with artificial light may have affected photoperiods
      • This can cause year-round shedding or prohibit development of a "winter coat"
  • The skin provides mechanical and biochemical protection
  • It is also a sensory structure for conveying information about pressure, pain, and temperature
  • The skin is composed of the epidermis and the dermis
    • The epidermis is the top layer; it's avascular and consists of epithelial cells attached to the dermis
• In hairless areas, keratinocytes produce keratin, serving as the protective outermost layer
• Dermis: made up of connective tissue, blood vessels, and nerve fibers
• Sebaceous glands: Small lobulated glands associated with the hair follicle
  • They empty sebum, a lipid compound, into the follicle, covering and protecting the hair
  • Sebum gives hair a lustrous appearance, lubricates, protects the skin, and possesses anti-microbial properties
  • Abnormal sebum is often associated with infections
  • Dogs have minimal sweat glands in skin
  • Perspiration from their sweat glands is ineffective for heat loss
  • Most sweat glands are in the nose and paw pads
    • A watery nose means a dog is sweating
    • A dry nose means there is no sweat
  • Cats groom themselves and the saliva deposited in hair helps dissipate body heat through evaporation
  • Dogs pant to dissipate heat
• Healthy skin will be pliable and free of dirt, sores, excessive oil, or dryness

Mucous Membranes

• Lubricating membranes that line body openings (mouth, nostrils, eyelids, anus, and reproductive tract)
• Contain blood vessels close to the surface, creating a light pink to pink appearance
• Mucous membranes that are pigmented, you won't be able to see color
• Color and refill time indicate the amount and composition of blood flow to the extremities
  • Pale mucous membranes can indicate decreased red blood cell (RBC), blood loss, or reduced blood flow
    • Anemia (loss or destruction of RBCs) or shock could be the reason for blood loss
  • Jaundiced or icteric (yellow colored) mucous membranes
    • Result of bilirubin accumulation
    • Bilirubin is a waste product that is produced when hemoglobin is catabolized by the liver
    • Liver unable to metabolize hemoglobin normally or an increased rate of red blood cells results in jaundice
• Bright red mucous membranes: Indicate a hyperdynamic state (early compensated shock) or irritation
• Cyanotic (bluish or purple) mucous membrane: A lack of oxygen in the blood
• Capillary refill time (CRT) can be used to evaluate the blood flow to extremities
  • Lift the upper lip, press the thumb firmly against the gum area above for 6-8 seconds
  • After release, the blanched area should return to normal color in 1-2 seconds
  • If it is prolonged, it can indicate circulatory collapse or shock

Body Temperature

• Normal body temperature of a dog is between 100-102.5 degrees Fahrenheit
  • Stress levels at the hospital can cause their temp to rise to 103, which can be normal
  • Rectal temperatures a more accurate
  • Axillary and auricular (ear canal) temperatures can also be taken
• If the fever is pyrexia, it is a metabolic cause of an increased temperature
  • When the fever is pyrexia, the body has raised the set point higher
    • The underlying problem needs to be treated before cooling them
• Fever due to environmental cause is from an external factor of rising temperature and pets cannot dissipate the heat
  • The patients will appear more stressed and will be trying to dissipate the heat
  • These patients need to be cooled down

Pulse

• The local, rhythmic expansion of an artery that corresponds to each contraction of the left ventricle of the heart
  • Pulse can be taken by palpating the heart or feeling it in the femoral artery of proximal inner rear leg or by gently pressing on the lower chest wall immediately behind the dog's shoulder
  • Dog normal 60-140 beats per minute
  • Smaller dogs have a faster heartbeat
  • Larger dogs have a slower heartbeat
  • Cat normal heartbeat: 120-140 beats per minute
  • Pulse rate and heart rate should be the same

Respiration

• Respiration rate refers to the number of inhalations (or exhalations) per minute
  • Dog normal: 10-30 breathes per minute
  • Cat normally: 20-40 breathes per minute
  • Count the breaths by watching the movement of the rib cage
  • Panting does not need to be counted and can be normal in a dog

Female Anatomy

• Major organs of the female reproductive tract: Oviducts, uterus, vagina, vulva, and the secondary sex organs, the mammary glands
• The ovaries are caudal to the kidneys
  • Small lima-shaped organs
  • The ovaries produce the egg and certain reproductive hormones
  • Oviducts: Small thin tubes connecting the ovaries to the uterus
    • They transport the ova (egg) from the ovaries to the uterus
    • The Ova (egg) will spend about 2 days moving through oviducts to the uterus
    • Fertilization takes place in the oviduct
      • For dogs, fertilization often takes place near the end of the oviduct (closer to the uterus)
  • Cat ova (egg) is ready for fertilization immediately anywhere in the oviduct upon ovulation
  • The uterus is a hollow, muscular, y-shaped organ consisting of 2 long horns and a short body, neck and cervix
  • The cervix is the oval-shaped fibrous/muscular structure that serves as the channel from the uterus to the vagina
  • The vagina (birth canal) is a long narrow muscular/membranous canal extending from the cervix to the vulva
  • Dog's vagina is lined with stratified, squamous epithelial cells that change in shape and structure during the estrous cycle
    • This can be used as a method for detecting ovulation in the dog
  • The urethra is the canal that carries uterine from the balder and empties into the lower parts of the vagina
  • The secondary sex organs of the female are the mammary glands
    • Most female cats have four functioning pairs of mammary glands, located in two parallel rows along the ventral mid-to-caudal abdomen
    • Dogs have 4-6 pairs in two parallel rows
    • Mammary glands are not developed until puberty
    • Teats deliver milk to puppies/kittens

Reproductive Anatomy of the Male

• Testes (testicles): Paired organs for sperm production and testosterone synthesis
• Sperm production occurs year-round in dogs and cats exposed to natural light
  • Decreased spermatogenesis in winter, but can mate year-round
  • The testes are divided into lobules, each containing long, tightly coiled seminiferous tubules
    • Cells lining the seminiferous tubules- the germinal cells- are responsible for spermatogenesis (production of spermatozoa)
    • Testosterone is necessary for normal spermatogenesis, secondary sexual characteristics in males
  • Each epididymis empties into associated vas deferens, which empty into the urethra
  • The urethra: Hollow tube runs from the bladder through the penis
  • Prostate accessory sex gland
  • Accessory sex glands: -The male cat has the prostate and the bulbourethral gland
    • Add secretions to the sperm containing fluid as it leaves the vas deferens and travels through the urethra

Dog Penis

• The glans of the penis (free portion of the penis), there is a small bone called (the os penis)
  • The Os gives the penis support during the early stages of mating
  • At the end of the os penis is a penile swelling called the bulbous glands
  • This area enlarges during mating
  • This is responsible for the "coital tie,”which prohibits separation
    • It can last 5-80 minutes

Cat Penis

• Positioned slightly downward and caudally when erect which allows intromission when the male mounts a receptive female
• Unique characteristic: The external surface of gland portion has barb-like projections to walls of the female's vagina, stimulating luteinizing hormone surge
• Luteinizing hormone (LH stimulates testosterone secretion -FSH initiates spermatogenesis and the production of androgens

Male Anatomy

• Pituitary gland produces luteinizing hormone (LH) and follicle stimulating hormone (FSH)
• Luteinizing hormone (LH) will stimulate testosterone secretion by the Leydig cells
• FSH initiates spermatogenesis and androgens production

Estrous Cycle

• Four stages: Anestrous, proestrus, estrus, and diestrus
• "Heat" or 'season" is only the estrus stage
• The female receptive to the male at this time and ovulation takes place
  • Dogs are spontaneous ovulators
    • Can ovulate even if not mated to a male
    • Cats are induced ovulators
    • Increases chances of successful reproduction when living a solitary life

Anestrus

• Period of reproductive rest
• Ovaries are not active; baseline estrogen and progesterone
• Happens after diestrus and before proestrus once the cycle starts again
• Males are not attracted to the females, and the females will not allow breeding
• In dogs, it starts after whelping (if a dog has gone through a pregnancy after birth)
  • Duration varies with each dog
  • Range seen is 2-10 months
  • Average is 5.5 months, which is about 8 months that an estrous cycle lasts
• Cat anestrus usually starts in October and lasts until late December
  • Can be shortened in queens who are kept indoors under artificial light for 12 hours

Proestrus

• Hormonal changes occur; The anterior pituitary secretes FSH, activating ovaries to begin follicular development and produce estrogen
• Estrogen triggers behavioral changes and prepares the uterus and vulva/vagina for mating and pregnancy
• Estrogen concentration steadily increases as the follicles develop in preparation for ovulation
• Proestrus ends with estrus, when the female allows the male to mount and breed

Dog Proestrus

• Dogs exhibit blood-tinged vaginal discharge and vulvar swelling
• Vulva is turgid and intromission/breeding is difficult at the beginning of proestrus
  • Vulva becomes softer and more pliable as time passes
• Blood-tinged vaginal discharge comes from the leaking of red blood cells of vessels of uterus into the lumen of the uterus, with some leakage from the wall of the vagina
• Proestrus lasts 6-11 days on an average of 9 days for dogs
• Dogs want to play with males but will not allow them to mount
• Female becomes more passive about the males approach as proestrus goes on

Cat Proestrus

• The cat shows subtle behavioral changes
  • Includes attention-seeking, increased restlessness rubbing
• Female will not allow mating but may allow the male to mount, if approached
• At the end of proestrus, the female's rubbing behavior will progress to calling; A tomcat will respond with a similar call
• Short, lasting between 1-3 days

Estrus

• Characterized by a period of sexual receptivity in the female
• There is decline in circulating estrogen and an increase in circulating

Dog Estrus

• Starts the day the female will stand for mounting, ending when the female will no longer accept the male
• Behaviors: Receptivity, allowing male during interactions, crouching and elevating the rear quarters toward the male, tail deviation, male mounts will tail to one side, tensing rear legs to support the weight
• Vaginal discharge progresses to a straw color or slightly pink color
• Dogs produce pheromones during estrus that attracts male
• Average duration: 5-9 days, however it can last a few days to almost 3 weeks
• Hormonal influences include a decline in estrogen and an increase in progesterone
  • Which stimulates the of release FSH and LH causeing gland, triggering in turn, ovulation
  • Estrus, smaller breeds 2-10 released ova; larger breeds release 5-20 ova
• All ova will have of development levels
  • Ova will be be capable of complete meiosis when when its released
• Capacitation is the process of maturation of the ova for become fertilized.
  • Process lasts 2-3 days.
  • Once mature it for hours over the over 12-72.

Cat Estrus

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