Canine Reproduction: Estrus, Breeding, and Hormones

Introduction

• Email Meera Gatlin with questions to Wildlife Bldg #room 115.
• There is no syllabus.
• Exam questions will come from power point and lectures.

Canine Learning Objectives

• The canine reproductive tract should be reviewed in both the bitch and dog, including its relevance in estrus, breeding, and copulation.
• Focus on the hormonal changes that occur in the canine estrous cycle and how to link them to behavioral and clinical changes.
• Visually identifying cytological changes during each stage of the canine estrus cycle is also important.
• Ovulation timing for optimal breeding management should be discussed.
• Focus should be conveyed on the importance of hormonal physiology in health concerns like pyometra, ovarian remnant syndrome, benign prostatic hypertrophy, and in spay/neuter guidelines.
• The parameters used to evaluate canine semen should be listed.
• Consider describing placentation type found in canine
• Understanding the physiology of pregnancy and parturition.

Reproductive Anatomy - Bitch

• The ovaries are caudal to the corresponding kidneys.
• Ovaries are located within the ovarian bursa.
• The ovaries measure 1 to 3cm.
• Stages of ovarian activity pictured are
  • Primary follicles
  • Maturing follicles
  • Graafian follicle (oestrogen)
  • Ruptured follicle
  • Corpus luteum (progesterone)
  • Retrogressive corpus luteum
  • Corpus albicans
• Uterine Tubes (AKA Fallopian Tubes, Oviducts) which transport oocytes from the ovary to the uterus with section including:
  • Ovarian end: Infundibulum with fimbriae
  • Middle: Ampulla, where fertilization occurs
  • Uterine end: Isthmus with crypts for sperm docking
• The Uterotubular Junction prevents backflow from uterus.
• Bicornuate uterus is suspended by the broad ligament
• The long uterine horns contain the developing embryos
• Short uterine body is where the two horns meet
• The Cervix is a short, thick-walled muscular sphincter that connects the uterus with the vagina and is located within the abdomen, averaging 1.5-2cm in length.
• The Vagina is oriented along the longitudinal axis of the body.
• The epithelial lining undergoes hormonal changes during estrus.
  • Proestrus: Vaginal mucosa is edematous and pink.
  • Estrus: Vaginal mucosa becomes a pale pink, and reduction in edema causes a crenulated appearance.
  • Diestrus: Mucosa appears patchy and hyperemic, and tissue is irritable.
• The Vestibule is a section between the lips of the vulva and the vagina
• Mammary glands: Typically have 10 (range 8-12), with two thoracic, two abdominal and one inguinal on each chain, arranged in bilaterally symmetric rows.

Canine Puberty

• Occurs between 6 and 24 months.
• Influenced by
  • Breed
  • Size
  • Environment
  • Body Condition
• Familial repro history important for predictions
• First heats less predictable, can be split

Canine Hormones

• FSH affects ovarian follicular development, preparing the repro tract for coitus.
  • Estrogen (-) feedback on FSH stimulates LH
• LH starts estrus, transitioning to luteal phase, where follicle ruptures, forming CL, which releases P4.
  • P4 causes behaviors and prepares repro tract for fertilized ova
• P4 or progesterone, if pregnant, from CL inhibits GnRH to prevent more follicles and maintain pregnancy
• If not pregnant, CL regresses, lifting negative feedback, restarts cycle

Canine Estrous Cycle

• Monoestrous.
• Non-seasonal (?)
• Cycle typically twice yearly, but can range from 1 -4 times a year
• The cycle is broken up into the follicular and leuteal phases
• Follicular: anestrus, proestrus
• Luteal : estrus, metestrus, diestrus

Canine Estrous Cycle Phases

• Proestrus (Follicular Phase)- lasts 9 days
  • Behavior is that Bitch is attractive to males but unwilling to stand/mate
  • Vulvar swelling with serosanguinous discharge is clinical
  • Hormonal: Estradiol peaks and Progesterone begins to rise in late proestrus
  • follicle development is physiology
  • Cytologic: Mixed epithelial cells, extracellular bacteria, red and white blood cells are visible on vaginal smear; White Blood Cells in early to mid-proestrus
• Estrus- lasts 9 days
  • Bitch behaviour is now receptive to mating
  • Clinically the Vulva softens but is still swollen and vaginal discharge gradually lightens in colour
  • Hormonal effects include Estradiol drops to basal concentrations and progesterone increases rapidly, along with LH surge
  • Physiology is that follicles ovulate primary oocytes which must undergo a final meiotic division to secondary oocytes and CL (corpora lutea) develops
  • Cytologic the Vaginal Smear shows - >90% cornified epithelial cells, +/- Extracellular bacteria and Reducing RBC, with rare to no WBC
• Diestrus (Luteal Phase)- lasts 2 months
  • Behaviour is that the Bitch now isn't receptive to mating
  • ClinicLly- Vulva decreases in size, May continue to see some vaginal discharge for the first dew days of diestrus, +/- Mammary development with lactation in late diestrus.
  • Hormonal- Low estradiol and elevated progesterone as CL present regardless of pregnancy status
  • Physiology- N/A
  • Cytology- >50% parabasal and intermediate epithelial cells WBC may be present (even abundant) in early diestrus and Reduced RBC relative to proestrus
• Anestrus
• Four Months Duration
• Bitch is not receptive to mating and Vulva continues to reduce in size
• Estradiol is low and progesterone as well
• FSH and LH pulses increase in late anestrus

Canine Estrous Correlation w/ Hormone Levels

• The four stages correlate with hormones: -Note for LH surge from follicular release -Note first rise in progesterone -Note progesterone rise continues

Tools to understand hormones

• Vaginal Cytology
• Progesterone Testing
• LH testing

Vaginal Cytology Tips

• Useful tool evalution for estrus cycle progression
• Bioassay for estrogen levels, can’t quantify
• Sample vagina, not vestibule, moistened swab
• Part lips, advance dorsally cranially SLOWLY
• Spin swab to collect cellular material
• Roll sample onto slide in unidirectional fashion and Diff-quick stain

Phases of Vaginal Cytology and Key Cells

• There are 4 Phases
  • 2 Non-Cornified
    • Parabasal
    • Intermediate
  • 2 Cornified
    • Superficial
    • Anucleate
• Parabasal:
  • Seen in diestrus and anestrus
  • Not uncommon in early proestrus
  • Conspicuously absent in estrus
  • "Fried egg" appearance

Vaginal cytology cells

• Small- round or oval with a moderately sized nuclei
• Large - slight polygonal shape with large Nucleolus /cytoplasm ratio, Seen in proestrus
• Early cornification seen in late proestrus into estrus, nucleus is undefined or very small and polygonal or “cornflake” shape is Evident
• Full cornification seen in estrus, nucleus is absent and polygonal or “ cornflake” shape is Evident
• Often seen in diestrus folllowing copulation, the vagina is NOT a sterile environment, but can be seen in proestrus especailly with the RBCS present

Bacteria Notes

• Mixed Population of Extracellular bacteria is normal and should evaluate for intracellular in nutrophils

Serum Progesterone Levels

• Serum Progesterone (ng/mL)
• At or near LH surge (1.0-1.9 ng/mL) and has about 2 + days remaining

The Boys: Male Canine Repro Anatomy

• Penis musclocavernous tissue os penis helps with intromission bulbus glandis engages copulatory lock, os penis elasticity base of penis allow 180 turn
• Testes within scrotum Oblqiue and Dorso positioning Long Axis

Male Canine Sexual Behavior

• Puberty with ejaculation at 1 year old

• Behaviors not always Sexual in Mature

Male Canine Natural Breeding

• Penetraton Penis vaginal os prior after Deflecting the rigidity prepuce Bulbus in after rigidity Deflecting

Semen Evaluation

• Need Artificial, Lubricants
• Evaluate Fractions color Opacity volume
• Evaluate Concentration and Motility, Morphology Count

Breeding Management Decision making

• ovulation cycle
• sperm availability
• processing
• types of breeding: - Natural service, SideFresh AI, Chilled Frozen Pregnancy and Part

Pregnancy

• Fertilization Occurs after UTERINE
• migration days
• ~16-18 Post surge embryo CANINE

Diagnosis

• PALPATION Ultrasound RELAXIN radiography

Parturition

•

• temperature °F 97 correlates progesterone -Mammary development

Feline Reproduction

Learning Objectives

• Review the feline reproductive tract in the queen and tom and its relevance in estrus and copulation.
• Discuss seasonality and how it affects feline reproductive physiology.
• Understand the hormonal changes that occur in the the feline estrous cycle and how it differs from the canine.
• Evaluate the importance of induced ovulation and how this affects feline breeding programs.
• Compare and contrast the physiology of pregnancy and parturition in the feline and canine species.

Queen Anatomy

• Similar to the bitch
• Long uterine horns
• Short uterine body

Seasonality

• Seasonally polyestrous
• Long day breeders that are photoperiod dependent
• Require >12hrs of daylight for cyclicity
• Cycle from about Feb through Sept/Oct( northern hemisphere)
• Less seasonally dependent near the equator
• Estrus can be controlled by light exposure
• Inhibit folliculogenesis with <8hrs of light
• Puberty begins 5-9m0 of age
• based on season when born

Feline Estrous Cycle

• Proestrus
• 1-2 days average duration
• Seen in <1/4 of cases
• Rubbing of head and neck,

Estrus

• Period of sexual receptivity
• Occurs during peak follicular activity
• Average duration 7 days (anywhere from 2-19 days)

Diestrus

• Only occurs if the cat has (induced) ovulation
• High serum progesterone (>1-2 ng/mL) from CL
• Interestrus AKA Postestrus
• Period following estrus IF the queen failed to ovulate / copulate
• Duration 8-10days
• Low plasma estradiol
• No sexually receptive behavior
• Will cycle with pro/estrus if there is no (induced) ovulation Anestrus
• Period of seasonal absence of cycling
• Typically autumn/winter in northern hemisphere (Oct -Feb)
• Baseline plasma estradiol and progesterone

Feline Oocyte Maturation

• Coitus is induced upon the Queen of population

Tpm (Male) Testes

• Can be located perineally Has a Free Movement till puberty
• Shaft can be of the ventral penis Location Scrotum And Has capacity For Director caudilliate Can be initially Achieved inside the prepuce Location can be broken at After Achieved inside

Semen

Has Artificial Vagina

• Some Data suggest it is Very Relativwly Performed

has ex Capua Ejaculation

Note that AI very rarely in cats

• Has important to time the Queen and have Natural ovulation

There Also Some Important Aspects Can have Artificial Vagina and It Stimulate

Pregnancy

60 and It Averages between 63 With a 65-Day Timeframe

Gestations

• Can have Hormone Levels Is that Lh has Primary Progesterone throughout With G

• Has a tonary placental relationship in Canines

Diagnosis

• Has Ultrasound That Can Determine By Abusing from Day

Feline