Question

The days of maternal recognition of pregnancy in different animal species are given below:
(A) 12-13 days for ewe
(B) 7-10 days for goat
(C) 16-17 days for cow
(D) 14-16 days for mare
Choose the correct answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (A), (C) and (D) only.

Hint:

Remember that in ruminants (cows, ewes, goats), the signal for MRP is Interferon-tau. The timing corresponds to just before the scheduled day of luteolysis: day 12--13 for ewes, and day 15--17 for cows and goats.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Maternal Recognition of Pregnancy (MRP) is the physiological process by which the embryo signals its presence to the maternal system, preventing luteolysis (the destruction of the corpus luteum) and ensuring the continuation of progesterone secretion required to maintain pregnancy.

Step 2: Detailed Explanation:
Each domestic animal species has a critical time window during the estrous cycle when this signal must be delivered:
- Ewe (A): MRP occurs around 12--13 days post-ovulation, mediated by the secretion of Interferon-tau (IFN-$\tau$) by the trophoblast, which blocks the upregulation of oxytocin receptors in the endometrium. This statement is correct.
- Cow (C): MRP occurs around 16--17 days post-ovulation, also mediated by Interferon-tau. This statement is correct.
- Mare (D): MRP occurs around 14--16 days post-ovulation, mediated by the constant movement of the embryonic vesicle throughout the uterine horns. This statement is correct.
- Goat (B): MRP in goats occurs around 15--17 days post-ovulation (also mediated by IFN-$\tau$). The statement claiming it occurs at 7--10 days is incorrect, as this is too early in the luteal phase of the caprine cycle.
Therefore, statements (A), (C), and (D) are correct.

Step 3: Final Answer:
The correct combination is (A), (C), and (D) only, corresponding to option (D).