Question

At what stage, dairy cattle attain puberty

• A. On attaining 25-30% of mature body weight
• B. On attaining 35-45% of mature body weight
• C. On attaining >50% of mature body weight
• D. On attaining >65% of mature body weight

Hint:

Heifers attain puberty when they reach 50--60% of their mature body weight, but they are typically bred (first service) only when they reach 60--65% of their mature weight to ensure safe calving.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Puberty in dairy heifers is defined as the stage of development when they first exhibit estrus accompanied by ovulation, indicating the onset of reproductive capability.
The onset of puberty is influenced by age, breed, genetics, and nutrition, but it is most closely correlated with body weight.

Step 2: Detailed Explanation:
In dairy cattle, the initiation of puberty is triggered by the maturation of the hypothalamus-pituitary-ovarian axis, leading to the pulsatile release of GnRH and LH.
Studies in animal husbandry show that heifers must reach a critical threshold of physical growth and body fat composition before these endocrine pathways are activated.
This threshold is best expressed as a percentage of their expected mature adult body weight.
Generally, dairy heifers attain puberty when they reach approximately 50% to 60% of their mature body weight (typically around 250 to 300 kg depending on the breed).
Achieving this target weight depends heavily on the plane of nutrition; heifers on a high-plane diet will reach this threshold and attain puberty at an earlier age (e.g., 9-12 months) compared to those on a low-plane diet (e.g., 15-18 months).
Therefore, the minimum stage at which dairy cattle attain puberty is on attaining >50% of their mature body weight.

Step 3: Final Answer:
Dairy cattle attain puberty on attaining >50% of their mature body weight.