AAVSB Reproductive Medicine and Theriogenology 1 — Questions and Answers
Question 1: In cattle, which hormone is primarily responsible for causing luteolysis at the end of the estrous cycle?
- Prostaglandin F2α (PGF2α) (Correct answer)
- Luteinizing hormone (LH)
- Follicle-stimulating hormone (FSH)
- Oxytocin
Correct answer: Prostaglandin F2α (PGF2α)
Prostaglandin F2α released from the endometrium causes regression of the corpus luteum, ending the luteal phase of the estrous cycle in cattle.
Question 2: What is the average gestation length in horses?
- 270 days
- 283 days
- 335 days (Correct answer)
- 365 days
Correct answer: 335 days
The average equine gestation length is approximately 335–340 days, though it can range from 320 to 370 days depending on season and breed.
Question 3: Which of the following species is classified as an induced ovulator?
- Cow
- Mare
- Cat (Correct answer)
- Ewe
Correct answer: Cat
Cats are induced ovulators, meaning ovulation is triggered by the mechanical stimulus of copulation rather than occurring spontaneously.
Question 4: During early pregnancy in cattle, the corpus luteum is maintained primarily by which substance secreted by the embryo?
- Progesterone
- Bovine trophoblast protein-1 (bTP-1) (Correct answer)
- Estrogen
- Relaxin
Correct answer: Bovine trophoblast protein-1 (bTP-1)
Bovine trophoblast protein-1 (bTP-1), also called bovine interferon-tau, is secreted by the conceptus to prevent luteolysis and maintain the corpus luteum during maternal recognition of pregnancy.
Question 5: In the bitch, which phase of the estrous cycle is typically the longest and is characterized by uterine quiescence?
- Proestrus
- Estrus
- Diestrus
- Anestrus (Correct answer)
Correct answer: Anestrus
Anestrus is the longest phase in the bitch's reproductive cycle, lasting approximately 4–5 months and representing a period of reproductive inactivity between cycles.
Question 6: Which serum hormone level is most commonly monitored to determine the optimal breeding time in bitches?
- Estrogen
- Progesterone (Correct answer)
- LH
- FSH
Correct answer: Progesterone
Serial progesterone assays are used to time breeding in dogs because progesterone begins rising at the LH surge and ovulation occurs at approximately 4–8 ng/mL.
Question 7: What is the term for primary uterine inertia in which the myometrium fails to generate adequate contractions to expel the fetus?
- Cervical stenosis
- Fetomaternal disproportion
- Primary uterine inertia (Correct answer)
- Hydrops allantois
Correct answer: Primary uterine inertia
Primary uterine inertia occurs when the uterus fails to contract effectively from the start of parturition, often due to uterine overdistension, hypocalcemia, or exhaustion.
AAVSB Reproductive Medicine and Theriogenology 1
In cattle, which hormone is primarily responsible for causing luteolysis at the end of the estrous cycle?