Contraception (ANISCI 103 exam #1)

increasing population

• guard resources (land, habitat, water)

• breeding

• artificial insemination

decrease population

• take away resources

• contraception/sterilization

contraception

prevention of pregnancy through the use of nonsurgical/surgical procedures

MALE - surgical options

castration

vasectomy

epididymectromy

emasculator

castration

elimination of the testes

vasectomy

removal of a segment of the ductus deferens

• reversibe

epididymetomy

removal of a segment of the epididymis

emasculator

crushes and cuts the spermatic cords

crimps and cuts

MALE - nonsurgical contraception

separation of the sexes

castration

• burdizzo: cutting off blood supply to testes by crushing the spermatic cords which causes them to atrophy but scrotum stays intact

• elastrator band: cuts off blood supply to testicles

• intratesticular injection - chemical castration

• hormones

• immunocontraception

intratesticular injectable solution

zinc gluconate solution injected in the testes of puppies 3-10 months when their testes are 1-2.7cm wide

2.5 months later

• the seminiferous tubules atrophy

• morphologic changes to sertole and leydig cells

• impaired spermatogenesis

adavantage + disadvantages of intratesticular injection

advantages: rapid to administer and easy, suited to remote locations, good for large populations, permanent, effective

disadvantages: expensive, not instantaneous, risk of tissue damage if not administered properly → painful, both neutersol and zeuterin stopped production

hormones

use reproductive steroids (natural/synthetic) to cause negative feedback, which effectively shuts down the hypothalamic-pituitary-gonadal axis

FEMALES - surgical contraceptions

ovariohysterectomy: removal of the ovaries & uterus (spay)

ovariectomy: removal of the ovaries

salpingectomy (birds): removal of oviducts

FEMALES - nonsurgical options

separation of the sexes

hormones

immunocontraception

intrauterine device

gene therapy

progesterone formulations → hormones

oral - megesterol acetate, altrengest

injectable forms or subcutaneous implants - progesterone (natural), medroxyprogesterone acetate, melengestrol acetate

• must wear gloves

progseterone in herbivores vs carnivores

herbivores: effective, relatively safe, few side effects

carnivores: effective

• major side effects: weight gain, lethargy, hyperplastic (not cancerous)/ neoplastic (cancerous) mammary changes

  • pyometra → infection of uterus

  • diabetes mellitus → high blood sugar levels

  • addison’s disease → adrenal gland fails to produce enough cortisol/aldosterone

gonadotropin releasing hormone

sustained exposure to gonadotropin releasing hormone = decrease in follicle stimulating hormone and luteinizing hormone

gonadotropin releasing hormone AGONIST

• agonist is a chemical that binds to a receptor and activates the receptor to produe a biological response

formulation of gonadotropin releasing hormone

intramuscular or subcutaneous injections

subcutaneous implant (slow release)

• suprelorin deslorelin

• leuprolide

• lutrelin

gonadotropin releasing hormone for carnivores

needed every 6-12 months

immunocontraception

• stimulate production of antibodies that bind to and interrupt reproductive proteins

• use of an animal’s immune system to prevent fertilization or conception

target: Zona Pellucida - immunocontraception

zona pellucida: glycoprotein membrane around the oocyte plasma membrane

antibodies against certain zona pellucia receptors will block sperm receptor sites and thereby prevent sperm attachment to egg → no fertilization

porcine zona pellucida vaccine

stimulates production of antibodies that prevent the attachment of sperm to ova → blocks fertilization

• recommends use for Artiodactyla, perissodactyls, pinnipeds, elephants and bears

  • short term use → 3-4 consecutive years

  • long term use in animals not essential for breeding programs

  • animals needing remote delivery of a contraceptive

35 mm autoclaved glass marble - horses intrauterine device

marble inserted into uterus 24 hours post ovulation while a mare is still in heat and the cervix is still relaxed

suppresses estrus due to pseudopregnancy (formation or a persistent corpus luteum) → prevents prostaglandin secretion from the uterus

gene therapy

intramuscular treatment delivering an anti-Mullerian hormone transgene → contraception in the domestic cat

expression of high levels of AMH did not impair sex steroid or estrous cycling

• prevented breeding induced ovulation