Theriogenology MCQS
1. In general, hormones are classified as proteins, polypeptides, and steroids. Which one of the following is a polypeptide?
a. Dopamine
b. Epinephrine
c. Progesterone
d. Oxytocin
Correct Answer: d. Oxytocin
Explanation: Oxytocin is a nonapeptide (a peptide containing nine amino acids). Dopamine and Epinephrine are catecholamines (amino acid derivatives), while Progesterone is a steroid hormone.
2. In the cow, at the time of ovulation, the oocyte will be at the:
a. Primary oocyte stage
b. Secondary oocyte stage
c. Tertiary oocyte stage
d. Ootid stage
Correct Answer: b. Secondary oocyte stage
Explanation: In most mammals, including the cow, the primary oocyte completes Meiosis I just before ovulation to become a secondary oocyte. It remains arrested in Metaphase II until fertilization occurs.
3. Which of the following hormones are transported in the blood in bound form?
a. Progesterone
b. Testosterone
c. Estrogens
d. All of the above
Correct Answer: d. All of the above
Explanation: Steroid hormones (Progesterone, Testosterone, and Estrogens) are lipophilic and poorly soluble in water; therefore, they must be transported in the blood bound to specific carrier proteins like albumin or sex-hormone binding globulins.
4. Pheromones are hormone-like substances that affect:
a. Other animals of other species through olfaction
b. Other animals of the same species through olfaction
c. Other animals of the same species through skin
d. None of the above
Correct Answer: b. Other animals of the same species through olfaction
Explanation: Pheromones are semiochemicals secreted or excreted by an individual that trigger a social or physiological response in members of the same species, primarily through the sense of smell (olfaction).
5. A rectally palpable positive sign of pregnancy in cattle at 45 days of gestation is:
a. Disparity in uterine horn size
b. Fluid fluctuation in uterine horns
c. Presence of a big CL
d. Presence of Amniotic vesicle
Correct Answer: d. Presence of Amniotic vesicle
Explanation: The amniotic vesicle becomes palpable as a small, turgid “pea-sized” object between 30 and 65 days of gestation. While horn disparity and fluid occur, the amniotic vesicle is considered a definitive (positive) sign.
6. Functionally, hCG is predominantly like:
a. Progesterone
b. LH
c. Estrogen
d. FSH
Correct Answer: b. LH
Explanation: Human Chorionic Gonadotropin (hCG) binds to the same receptor as Luteinizing Hormone (LH). Because of this, it is often used in veterinary medicine to induce ovulation or treat cystic ovaries.
7. Ovulation without behavioral estrus signs is called:
a. Silent ovulation
b. Sub ovulation
c. Silent estrus
d. Diestrus
Correct Answer: c. Silent estrus
Explanation: Silent estrus (or “quiet ovulation”) occurs when physiological ovulation takes place but the animal fails to show the typical behavioral signs of “heat.” This is common in the first ovulation after puberty or calving.
8. When a cow not in true heat is bred through A.I., it will result in:
a. Monozygotic pregnancy
b. Dizygotic pregnancy
c. Non-conception
d. Delayed conception
Correct Answer: c. Non-conception
Explanation: Successful conception requires the presence of a viable oocyte. If the cow is not in true heat, ovulation has either not occurred or happened at a different time, making fertilization impossible.
9. The primary oocytes are differentiated from:
a. Oogonia
b. Sertoli cells
c. Myoid cells
d. Connective tissue
Correct Answer: a. Oogonia
Explanation: Oogonia are the primordial germ cells in the female. They undergo mitosis and then differentiate into primary oocytes during fetal development.
10. The zygote undergoes cell proliferation to form:
a. Blastomeres
b. Cyst
c. Blastocytic degeneration
d. Antrum
Correct Answer: a. Blastomeres
Explanation: As the zygote begins to divide (cleavage), the individual cells produced are called blastomeres. These blastomeres eventually form the morula and then the blastocyst.
11. The process of parturition is initiated by the:
a. Mother
b. Temperature of uterus
c. Fetus
d. Age of the mother
Correct Answer: c. Fetus
Explanation: Parturition is initiated by the “fetal stress” response. The fetal hypothalamus-pituitary-adrenal axis releases cortisol, which triggers the conversion of progesterone to estrogen in the placenta.
12. The early pregnancy factor (EPF) has:
a. Immunosuppressive properties
b. Immunostimulating properties
c. Autoimmune properties
d. None of the above
Correct Answer: a. Immunosuppressive properties
Explanation: EPF is a protein that appears very shortly after fertilization. It has immunosuppressive properties to prevent the mother’s immune system from rejecting the “foreign” embryo.
13. The presence of progesterone in maternal circulation indicates:
a. Luteal activity
b. Maternal activity
c. Follicular activity
d. Fetal activity
Correct Answer: a. Luteal activity
Explanation: Progesterone is produced by the Corpus Luteum (CL). Therefore, its presence in the blood is a direct indicator of luteal activity and the absence of luteolysis.
14. pFSH stands for:
a. Porcine follicle stimulating hormone
b. Purified follicle stimulating hormone
c. Putrefied follicle stimulating hormone
d. Partially purified follicle stimulating hormone
Correct Answer: a. Porcine follicle stimulating hormone
Explanation: In veterinary pharmacology and superovulation protocols, “pFSH” specifically refers to Follicle Stimulating Hormone derived from porcine (pig) pituitaries.
15. Circulating concentration of which hormone is lowest at estrus in the cow?
a. Estradiol
b. Progesterone
c. FSH
d. LH
Correct Answer: b. Progesterone
Explanation: For a cow to enter estrus (heat), the Corpus Luteum must regress, causing progesterone levels to drop to basal levels. Meanwhile, Estradiol, FSH, and LH peak during or near estrus.
16. Which hormones cause the expression of behavioral signs of estrus in the cow?
a. Inhibin & estrogen
b. Estrogen & progesterone
c. Progesterone & GnRH
d. LH & FSH
Correct Answer: b. Estrogen & progesterone
Explanation: In the cow, behavioral estrus is caused by high levels of estrogen in the absence of progesterone. However, a small amount of “priming” by progesterone from a previous cycle is often necessary for the brain to respond to estrogen.
17. Immunization of a cyclic cow against oxytocin will lead to:
a. Prolongation of the cycle
b. Shortening of the cycle
c. No effect on the cycle
d. None of the above
Correct Answer: a. Prolongation of the cycle
Explanation: Oxytocin from the Corpus Luteum stimulates the uterus to release $PGF_{2\alpha}$. If oxytocin is neutralized by antibodies, the luteolytic signal is blocked, the CL persists, and the estrous cycle is prolonged.
18. Ovulation in cattle occurs:
a. At the beginning of heat
b. At the mid of heat
c. At the end of heat
d. 10-14 hours after the end of heat
Correct Answer: d. 10-14 hours after the end of heat
Explanation: Unlike many other species, cows are post-estrus ovulators. They typically ovulate approximately 10 to 14 hours after behavioral estrus has finished.
19. Sperm capacitation in the cattle mostly occurs in the:
a. Vagina
b. Cervix
c. Uterus
d. Uterus and fallopian tube
Correct Answer: d. Uterus and fallopian tube
Explanation: Capacitation—the final maturation of sperm required to fertilize an egg—takes place as the sperm travel through the female reproductive tract, primarily within the uterus and the oviduct (fallopian tube).
20. The length of the estrus cycle does not change in cattle if the embryo dies:
a. 10 days after conception
b. 16 days after conception
c. 17 days after conception
d. 19 days after conception
Correct Answer: a. 10 days after conception
Explanation: Maternal recognition of pregnancy in the cow occurs around day 16-17. If the embryo dies before this (e.g., day 10), the body does not “know” it was pregnant, and the cycle continues as normal (21 days).
21. In general, GnRH analogs functionally are:
a. more potent than natural GnRH
b. less potent than natural GnRH
c. equally potent to natural GnRH
d. None of the above
Correct Answer: a. more potent than natural GnRH
Explanation: Synthetic GnRH analogs (like Buserelin or Deslorelin) are modified to have a longer half-life and a higher affinity for receptors, making them significantly more potent than the endogenous hormone.
22. In cattle, oxytocin is synthesized in the:
a. Hypothalamus only
b. Hypothalamus and CL
c. Hypothalamus and pituitary
d. Posterior pituitary
Correct Answer: b. Hypothalamus and CL
Explanation: While oxytocin is classically known to be synthesized in the hypothalamus, in ruminants, the Corpus Luteum (CL) also synthesizes significant amounts of oxytocin to facilitate the luteolytic process.
23. From which duct of the embryo does the male reproductive system arise?
a. Mullerian
b. Wolfian
c. Oviduct
d. Bile duct
Correct Answer: b. Wolfian
Explanation: The Wolffian (mesonephric) ducts develop into the male reproductive tract (epididymis, vas deferens). The Müllerian ducts develop into the female tract.
24. The initiation of puberty in the bovine is largely a function of the animal’s:
a. Age only
b. Body weight only
c. Both age & body weight
d. Climate
Correct Answer: c. Both age & body weight
Explanation: Puberty is reached when an animal attains a certain age and a target percentage of its mature body weight (usually around 55-60%). One cannot occur without the other.
25. The first heat of a pubertal animal is often silent because of a lack of:
a. Progesterone
b. Estrogen
c. LH
d. FSH
Correct Answer: a. Progesterone
Explanation: The brain needs to be “primed” by progesterone before it can respond to the behavior-inducing effects of estrogen. Because there was no previous CL to provide progesterone before the very first ovulation, that first heat is usually silent.