Question

Given below are two statements, one is labelled as Assertion (A) and other one labelled as Reason (R).
Assertion (A) : Exogenous melatonin administration can be used to advance the onset of breeding season in ewes and does.
Reason (R) : Ewes and does are long-day breeders.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

To remember photoperiod responses:
- Short-day breeders (Sheep, Goats): Melatonin stimulates reproduction.
- Long-day breeders (Horses): Melatonin inhibits reproduction (light stimulates it).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Photoperiod (day length) plays a vital role in regulating reproduction in seasonal breeders.
The pineal gland translates light signals into hormonal signals by releasing melatonin, which is secreted primarily during darkness (nighttime).

Step 2: Detailed Explanation:
Let us analyze the reproductive physiology of sheep and goats:
- Assertion (A): Administering exogenous melatonin mimics the short-day photoperiod (long nights).
In seasonal small ruminants, this signal stimulates the hypothalamus to release GnRH, initiating the estrous cycle.
This technique is widely used in veterinary medicine to advance the breeding season. Thus, Assertion (A) is correct.
- Reason (R): This statement is incorrect.
Sheep (ewes) and goats (does) are short-day breeders, meaning they naturally initiate their breeding cycles in the autumn as day length decreases.
Mares are examples of long-day breeders. Thus, Reason (R) is false.

Step 3: Final Answer:
Assertion (A) is correct but Reason (R) is not correct.