Puberty in Heifers
Physiological events leading up to puberty
Endocrine and morphological events in peripubertal heifers are similar to the resumption of cyclicity post partum in mature cows.
- Decreased negative feedback of oestradiol
- Maturation of the hypothalamus
- Increased frequency of release of LH pulses
- Enhanced development of ovarian follicles
- Enough oestradiol produced to induce behavioural oestrus and a preovulatory surge of gonadotrophins
Puberty is attained with the first behavioural oestrus that is accompanied by ovulation and development of a corpus luteum with a typical lifespan.
What influences the onset of puberty in heifers?
Factors that can influence the pubertal rise in release of LH pulses are:
- genotype
- season of year when pubertal age is attained
- growth or nutritional intake
- social cues
- treatment with exogenous hormones
Standard values in pubertal heifers
There are slight differences in the age at which heifers reach puberty and start cycling. Body weight is one of the factors which strongly influence the onset of puberty in cattle.
| Breed | Age at puberty (months) | Weight at puberty (kg) |
|---|---|---|
| Holstein Frisian – US type | 12-13 | 265-289 |
| HF – Australian type | 8-12 | 200-230 |
| Jersey | 8-10 | 160-180 |
| Brown Swiss | 10-11 | 280-300 |
| Charolais | 12-13 | 320-355 |
| Angus | 13-14 | 300-310 |
| Hereford | 14-15 | 300-310 |
| Simmental | 11-12 | 320-330 |
| Zebu type | 17-27 | 330-350 |
