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Endocrine changes from birth to puberty in the heifer
S E Dodson1, B J McLeod, W Haresign
1A.F.R.C. Research Group on Hormones and Farm Animal Reproduction, University of Nottingham, School of Agriculture, Loughborough, Leics, U.K.
Journal of Reproduction and Fertility
|March 1, 1988
Summary
Puberty onset in cattle involves complex changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion. These hormonal shifts, crucial for reproductive development, occur gradually rather than abruptly before the first ovulation.
Area of Science:
- Reproductive Endocrinology
- Animal Science
- Veterinary Medicine
Background:
- Understanding the hormonal dynamics of puberty is essential for cattle breeding and management.
- Previous research has indicated shifts in gonadotropin secretion during bovine development, but specific patterns around puberty require further elucidation.
Purpose of the Study:
- To characterize the changes in luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion patterns in heifers from birth through the peripubertal period.
- To investigate the relationship between hormonal secretion patterns and the onset of puberty and first ovulation.
Main Methods:
- Blood samples were collected weekly from birth, with monthly 24-hour frequent sampling (15-minute intervals) from 3 weeks of age in 12 Hereford x Friesian heifers.
- Estrus detection was performed using an estradiol-treated steer, and ovulation was inferred from progesterone profiles.
Main Results:
- Mean plasma LH concentrations decreased from birth to 15 weeks, then increased to 39 weeks, primarily due to changes in LH episode frequency and amplitude.
- A short luteal phase preceded the first estrus, followed by a normal luteal phase in all heifers.
- No significant increase in LH or FSH parameters was directly associated with the onset of puberty.
Conclusions:
- The gonadotropic stimulus for the first ovulation in heifers appears to be abrupt.
- The study highlights the complex, non-linear changes in LH and FSH secretion leading up to puberty in cattle.