Lactation in sterile cows is induced by

Options

A. vitamin `B_(12)`
B. `stibesterol
C. gonadotropin
D. none of these

Answer

### Step-by-Step Solution:

1. **Understanding Lactation**: Lactation is the process of milk secretion from the mammary glands, which typically occurs after the birth of a young one. This is a natural process in female mammals.

2. **Sterile Cows Context**: In the case of sterile cows, they do not give birth to young ones, which means they do not naturally undergo the lactation process.

3. **Inducing Lactation**: To induce lactation in sterile cows, certain substances or hormones can be used. The goal is to stimulate the mammary glands to produce milk despite the absence of a calf.

4. **Identifying the Correct Substance**: Among the options provided (vitamin B12, Stibesterol, gonadotropin, or none of these):
- **Vitamin B12**: This vitamin is not related to the lactation process.
- **Gonadotropin**: While it is involved in reproductive processes, it is not specifically used to induce lactation in sterile cows.
- **Stibesterol**: This is a synthetic estrogen that has been used to induce lactation in sterile cows and immature females.

5. **Conclusion**: The correct answer to the question is **Stibesterol**, as it is the substance used to induce lactation in sterile cows.

### Final Answer:
Lactation in sterile cows is induced by **Stibesterol**.

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