Equine - Stallion Reproduction Flashcards
How is puberty described in a stallion?
-Able to produce an ejaculate consisting of 50 million spermatozoa and at least 10% progressive motility
OR
- Histologic evidence of mature spermatogenesis
OR
- Produce an ejaculate ‘capable’ of sustaining a pregnancy
When does puberty happen in the stallion?
Average 20-21 months, however it can happen anywhere between 12-24 months of age- very breed dependent (Warmbloods typically reach it sooner)
When are stallions typically sexually mature? Reach peak performance?
Mature by 3 years of age with peak performance at 4-5 years of age
When does testicular dissension begin? When is it completed?
It begins during the last month of gestation and is completed somewhere around 10-14 days post foaling
When do stallion produce semen?
year-round
When is a stallion’s peak semen production?
during the spring and summer
What changes happens in a stallion during long days?
Increased testicular size and weight, more sperm output, increased libido, and increased plasma concentrations
How is the equine testis oriented?
Horizontally - cranial (head of epididymis) to caudal (tail of epididymis) orientation
What accessory sex glands does the male horse have?
prostate, seminal vesicles, bulbourethral glands, and ampulla
What is the ampulla?
a dilation of the ductus deferens
What type of penis does the stallion have?
musculocavernous penis
How is an erection in the stallion achieved?
by venous vasoconstriction and arterial vasodilation to cause engorgement of the penile erectile tissue (corpus cavernosum and corpus spongiosum)
How would you describe the prepuce of the stallion penis?
It is a telescoping prepuce - it basically folds within itself when there is no erection
What are the components of the glans penis?
the urethral sinus and diverticulum, and fossa glandis
What is frequently accumulated in the glans penis? What management methods are done to this prior to semen collection?
smegma aka ‘bean’
It is washed prior to semen collection
Where are samples taken from for culture for CEM and other potential reproductive pathogens?
the glans penis
What should you wear when working with stallions and/or mares during collection and/or breeing procedures?
a helmet
What are the reasons for performing a stallion BSE?
Estimation of reproductive potential
Evaluation at the beginning of the breeding season
Determination of cause of poor reproductive performance
What are the objectives for performing a stallion BSE?
Determine physical and reproductive fitness
Quality and quantity of semen
Libido testing
Identification of reproductive pathology and/or reproductive disease
What is missing from the standard BSE?
fertility testing
What all occurs during breeding soundness examinations?
Getting a thorough history (type of insemination, book size, frequency of collection, reproductive disease screening), general physical examination, observation of libido, collection of semen, evaluation of semen
What are the components of a reproductive examination?
scrotal and testicular palpation, palpation of the spermatic cord, and examination of the penis upon obtainment of erection
What is measured when you do scrotal and testicular testes?
Size, symmetry, and consistency
The total testicular width - it is measured with an ultrasound
What should the total testicular width be in a fertile male?
greater than or equal to 80mm
What is the daily sperm output?
The daily amount of cells ejaculated = cells produced per day
How is daily sperm output measured?
Either collecting daily for 5 to 7 days for an accurate number or estimating it by collecting from the stallion twice approximately one hour apart
How is predicted sperm output calculated (not asking for a specific formula)?
Either by using testicular volume calculated from the testicular ultrasound or by using the total scrotal width
What can be observed/performed during a scrotal ultrasonography?
Acquiring testicular measurements and evaluating for calcification or masses
Examining the structure of the epididymis and evaluating for masses
Examining the spermatic cord for normal blood flow and presence of masses
What is considered the ‘length’ of the testes?
Measuring from the base of the tail to the base of the head
How should a normal testes look on ultrasound?
homogenous parenchyma, normal blood flow in the spermatic cord and testicular artery, no fluid or masses surrounding the testes
How would an abnormal testes look on ultrasound?
non-hemogenous parenchyma and fluid surrounding the structures of the testes
What should normal epididimes look like on ultrasound?
uniform echogenic tubular structure running from tail, body, and head along the testicular border
What will the pampiniform plexus look like on ultrasound?
Cheese cloth appearance with unifor vasculature throughout the cord
Uniform blood flow
What steps need to be taken prior to internal reproductive examination?
Frequently sedation is needed, stocks, and sedation
How is internal reproductive examination done?
transrectal palpation and ultrasound
What is observed during internal reproductive examinations?
seminal vesicles, prostate, ampullae, and bulbourethral glands
What will be present on ultrasound during an internal reproductive examination immediately post collection?
seminal fluid
How should the penis be washed?
With warm water only with cotton or WypAll towels and only wash below the preputial ring
Why do you only want to use warm water to wash the penis?
Because all detergents are spermicidal and potentially irritating to mucosal membranes
What is all ‘washed-away’ during penile washing?
Remove all gross debris from the penile shaft, rinse and remove all smegma and gross debris from preputial diverticulum - care must be taken to not irritate the urethra
Following washing of a penis, what should happen?
The cotten/towel used to clean should be rung out and the penis patted dry to remove all water (it is spermicidal too!)
Penile washing differs from what other washing method?
routine sheath cleaning that is performed with ivory soap and warm water
Routine sheath cleaning is done for what male horses?
both geldings and stallions
What sedative is frequently used for sheath cleaning?
xylazine/detomidine and/or twitch as needed
What personnel is needed for semen collection?
stallion holder, collector, washer(if not same as collector), bucket holder, and tease mare holder
What are the two different types of artificial vaginas?
Missouri AV and Colorado AV
List the pros and cons of the Missouri AV.
Pros: light weight and allows for simultaneous pressure at the base of penis and glans peis
Cons: loses temperature in cold climates
List the pros and cons of the Colorado AV.
Pros: Maintains temperature best in cold climates
Cons: Heavy, stallions ejaculate into water bladder which could affect sample if not released immediately following collection
What are some methods of semen collection using an AV?
Collection off of a jump mare or using a phantom mare,
What mares are used for jump mares?
estral mares or ovariectomized tease mares that have gotten estradiol cypionate IM
What are some alternative methods of semen collection?
Ground collection - basically trying to get him to thrust and ejaculate into the AV
Pharmacological ejaculation via administration of sedatives +/- imipramine to lower the ejaculatory threshold and cause ejaculation
When is ground collection done?
It is occasionally elected for stallions who cannot mount a phantom or jump mare
What is the % chance of producing a successful ejaculation with pharmacological ejaculation?
33%
When doing semen evaluation, what is observed microscopically?
motility, concentration, and morphology
If a client opts do do advanced semen evaluation, what is examined?
longevity tests/cooling trails, specialized staining, membrane function evaluation, or SCA
What is the desired percentage of progressive motility in a semen sample?
greater than or equal to 60%
What can be used to examine the concentration of semen?
hemocytometer, densimeter, and nucleocounter
What is the gold standard tool for measuring semen concentration?
hemocytometer
What semen samples can a densimeter only be used with?
raw semen
Note: this is the most common
What is a nucleometer used for?
measuring semen concentration that is being shipped, frozen, etc.
Note: it is the most expensive option
What stain should be done to examine semen morphology?
perform Eosin-Nigrosin stain or wet mount
How is the morphology of semen classified (determined)?
count and classify 100 cells and determine percentages of abnormalities
What is the desired percentage of progressive motility in a semen sample?
greater than or equal to 60%
What is the minimal dose of motile sperm during examination?
500,000,000 progressively motile sperm
What is the expected loss of sperm during 24 hours transport?
50% loss
What is the best extension amount for shipped sperm?
They survive best at 25-50 million/mL of extender
What is the industry standard for amount of sperm shipped?
1 to 1.5 billion motile spermatozoa
