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The Dog
male dogs are sexually active throughout the year without any influence of season
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Puberty
- when the dog releases spermatozoa in the ejaculate
- 9-12 months old, sexual maturity is not reached until 15-16 months old (some are 5-6)
- neuter 5, 6, 7 months old
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Normal testes
- descend into the scrotum a few days after birth...
- ...may be difficult to palpate at this time (wasilt withdrawn back into inguinal ring)
- present in scrotum by 8 weeks of age 9can be delayed as late as 6-8 months)
- >8 months - usually will not descend
- spermatozoa output is related to testis size
- - large dogs prodce more spermatozoa than small dogs
- cryptorchid makes neuter more of a surgery
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Spermatogenesis
- takes place in testes
- production of male gametes (sperm cells) 62 days
- during prepubertal period, differentiate into spermatogonia (primary germ cell - becomes spermatozoa) until puberty
- blood supply network & specialized muscular tissue maintains the temperature of blood supplying the testes below normal BT (body temperature)
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Spermatogonia
primary germ cell
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Spermiocytogenesis
- first stage of spermatogenesis
- - spermatogonia divide mitotically (seminiferous tubules) to produce new spermatogonia and primary spermatocytes
- - primary spermatocytes undergo meiotic division to produce secondary spermatocytes
- - secondary spermatocytes divide meiotically to produce spherical spermatids
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Spermiogenesis
- second stage of spermatogenesis
- - spherical spermatids mature into elongated spermatids
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Spermiation
- final stage of spermatogenesis
- - process of release of the elongated spermatids into the lumen of the seminiferous tubules as spermatozoa
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Crytorchidism
- failure of the testes to descend into the scrotum
- animal is said to be cryptorchid:
- - unilateral cryptorchid - one side or the other undescended
- - bilateral cryptorchid - both sides undescended
- can be genetically influenced
- more than one reason for cryptorchidism
- don't want to breed cryptorchid dog
- can sometimes find undescended testicle with ultrasound
- - fine white band around testicle if not atrophied (in dogs only)
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Prostate
- only accessory gland in the dog
- secretes a fluid which liquifies the coagulated semen
- located caudal to the neck of the bladder, encircles urethra (bladder to outside)
- androgen (male hormones) dependent (increases in size with testosterone secretion and decreases in size with estrogen secretion
- size of prostate gland increases with age...
- - benign prostatic hyperplasia
- signs of increased signs may inlcude constipation and straining to defecate
- - could also affect urethra
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Mating
- coitus
- - protracted procedure
- - can last up to 20 minutes
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Ejaculate
divided into 3 fractions
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First fraction of ejaculate
- presperm fraction
- clear fluid with little or no spermatozoa
- volume varies from a few drops to 10 mls
- produced while the dof is thrustig and attempting intromission
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Second fraction of ejaculate
- sperm rich
- milky in color due to presence of numerous spermatozoa
- volume varies from 1 ml to 2 mls
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Third fraction of ejaculate
- prostatic fluid
- clear fluid with few spermatozoa
- can be secreted for 15 minutes or more
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Manipulation of reproduction in the dog
- surgical castration
- chemical castration
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Surgical castration
- neuter
- removal of the testicles
- removew the source of testosterone
- prostate gland becomes smaller after castration
- reduces the amount of tissue build up (muscle) because testosterone is an anabolic steroid
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Chemical castration
- blocking of testosterone without actually removing the testicles
- production of spermatozoa is stopped because testosterone is needed to permit the production of sperm
- estrogen or progesterone
- Neutersol (TM)
- - injected into the testicle - topical anesthetic/sedative
- - necrotizing agent
- - 99.6% effective
- - male dogs, 3-10 months old
- - does not halt testosterone production completely
- - atrophy of the testicles, epididymus, and prostate gland
- - scar tissue formation which prevents movement of sperm from testicles through epididymus
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