Endocrine (repro/thyroid) Flashcards
Why might we need to manipulate the estrous cycle in cattle?
- It is difficult to tell when a cow is in estrus.
- To improve conception rates.
- To synchronize calving.
What are the four hormones used to manipulate the estrous cycle?
- Prostaglandin
- GnRH
- Progesterone
- Estrogen
What is the function of GnRH? Where is it released from?
GnRH is released from the hypothalamus and tells the anterior pituitary to release a surge of FSH and LH. It triggers the LH spike that induces ovulation.
What is the function of prostaglandin? Where is it released from?
Prostaglandin (PGF2α) is secreted by the endometrium and promotes luteolysis and uterine contraction, and relaxes the cervix.
True or False: All prostaglandins may cause adverse effects in mares.
True
True or False: Small animals are more sensitive to the effects of prostaglandin.
True
What are two differences between Dinoprost and Cloprostenol? (Both are PGF-2a)
- Dinoprost is labelled for cattle, horses, and swine, but Cloprostenol is labelled for cattle and swine only. However, Cloprostenol is still used for horses due to fewer side effects.
- Dinoprost has a shorter half-life.
What is the function of progesterone? Where is it released from?
Progesterone is secreted by the corpus luteum and sends negative feedback to the anterior pituitary to stop FSH and LH production. It prevents ovulation and maintains pregnancy.
What is the function of estrogen? Where is it released from?
Estrogen is secreted by the granulosa cells in the follicle and causes estrus behavior. It also induces the LH spike and stimulates mammary development.
True or False: Estrogen is commonly used in veterinary medicine.
False. It is not widely used in vet med, especially not in food animals because of human health/food safety concerns.
True or False: Manipulating the estrous cycle is the same protocol in beef as it is in dairy cattle.
True
What is a CIDR (controlled internal drug release) device?
An intravaginal progesterone insert used in conjunction with hormones to synchronize estrus in dairy cows.
Which hormone is the active ingredient in a CIDR?
Progesterone
What is Melengestrol acetate (MGA)?
An oral form of progesterone that suppresses estrus in feedlot heifers.
Why might we need to manipulate the estrous cycle in horses?
- To move the cycling season earlier.
- To shorten the transition between non-cycling and cycling.
- To induce ovulation.
- To suppress ovulation.
Which two drugs are used for inducing ovulation in mares?
- Human chorionic gonadotropin (hCG)
- Deslorelin (a synthetic GnRH analogue)
What is the most common drug used in theriogenology?
Progesterone
What is progesterone mainly used for in horses?
To maintain pregnancy in high-risk mares.
Why is estrous cycle manipulation much less common in small animals than large animals?
It is very unreliable and small animals are a lot more sensitive to the side effects.
Why might we want to induce parturition in cows?
- To allow more postpartum time before next breeding.
- To attempt to reduce calf size/dystocia.
- To prevent excessive udder edema in dairy cattle.
- To take advantage of available forage for lactation.
What are two classes of drugs commonly used to induce parturition in cows?
- Glucocorticoids
- Prostaglandins
How do glucocorticoids and prostaglandins induce parturition in cows?
These drugs mimic fetal cortisol surges.
True or False: The combined use of glucocorticoids and prostaglandin will lead to faster induction of parturition in cattle.
True
True or False: Induction of parturition in mares is common.
False. This is not commonly done unless the mare is experiencing a life-threatening complication of pregnancy.
