Reproductive Biology in Mammals

Study Notes

Increase in estrogens speeds up turnover of vaginal epithelial cells, causing progressive cornification.
Cell color changes:
- Anestrus and proestrus: pink-purple
- Estrus and diestrus: blue-purple
Parturition occurs 58-72 days after breeding at an unknown stage of estrus.
Basenji: one estrous cycle per year.
Diagnosis methods:
- Radiographs: count litter size after 45 days
- Abdominal palpation: detect pregnancy at about 21 days
Impending parturition can be predicted by a transient temperature drop in the bitch.
LH surge peaks at behavioral estrus and acceptance of male, ovulation occurs 2 days later.

Birth occurs 64-69 days from breeding at an unknown state of estrus or 63 days from breeding at ovulation.
Diagnosis methods:
- Abdominal palpation: reliably detects pregnancy at about 21 days
- Ultrasound: detects fetal heartbeat at 28 days
- Radiographs: count litter size after 40 days
Obvious mammary development can be seen in the final 2 weeks.
Estrus cycle recurs every 2-3 weeks (interestrus interval).

Estrus behavior lasts 18 hours.
Signs of estrus:
- Standing to be mounted
- Riding other cows
- Restlessness
- Bellowing
- Ruffled hair or hair loss on tail head
Clear vaginal mucus discharge appears after estrus.
During diestrus, a cow has a soft corpus luteum.
Diagnosis methods:
- Placentomes can be felt at 70-75 days
- Membrane slip can be felt at 30-35 days
- Fremitus can be felt at 90-120 days
Freemartins:
- Sterile female calves born twin to a male
- Underdeveloped ovaries due to XY antigens crossing the chorionic placenta blood vessels
- Characterized by a short vagina and no cervix

Estrus detection rates: approximately 50-65%.
Calving interval: around 13 months.
First service conception rate: 40% or greater.
Average days open: around 115 days, ideally in the low 100s.
Services per conception:
- Pregnant cows: less than 2.5
- All cows serviced: less than 3.5
Number of cows in estrus on a given day:
- Divide the number of non-pregnant cows by 18 and then by 21.