Bovine Reproduction

Type of estrus cycle

Polyestrus

Average length of estrus cycle

21 days (range 18-24 days)

Onset of puberty

10-12 months

When should cows be bred for best conception rates?

Breeding at 15 months for calving at 2 years of age

Proestrus length

1-2 days

Estrus length

1-2 days

How long do signs of heat last?

Up to 18 hours

How often should you check for heat signs in cows?

3 times per day

When does ovulation occur?

• Within 24 hours of signs of heat

• Ovum lives for a maximum 24 hours

When should cows be bred in relation to ovulation for best conception rates?

6 hours before ovulation

Length of metestrus

1-3 days

How can you tell if a cow is in metestrus?

Vaginal discharge tinged with blood

Diestrus length

4-18 days

Does anestrus occur in cows?

No, only if pathological

When should cows be bred after parturition?

After 2nd heat cycle to give uterus time to heal

How long after calving can a cow begin cycling again?

Average of 30 days after parturition (2 weeks - 2 months)

When is heat detection most significant?

For artificial insemination

Signs of heat

• Decreased milk production

• Mounting behavior (will mount other cows and allow other cows to mount)

• Difficult to separate from herd

• Raised tail

• Head butting

• More active

• Following other cows

• Decrease appetite

• ± Vulvar swelling

• ± Clear mucoid vaginal discharge

Signs cow is past heat

• Will no longer stand to be mounted

• May still mount other cows

• Blood in vaginal mucous

When is estrus synchronization benificial?

• Ensures consistency in size of beef calves

• Useful for embryo transfer

Estrus synchronization products

• Prostaglandins (Lutalyse, Estumate, estroPLAN)

• Progestins (Easi-Breed CIDR, MGA)

• GnRH (Cystorelin, Factrel, Fergatyl)

Causes of reproductive failure

• Failure in estrus cycle

• Atypical estrus

Pathological anestrus causes

• Poor nutrition

• Stress

• Uterine/ovarian abnormalities

Causes of atypical estrus

• Persistent CL

• Cystic ovaries

How is persistent CL treated?

PGF2 Alpha

How are cystic ovaries treated?

GnRH

What breed of cows are cystic ovaries most common in?

Production Holsteins

What causes failure in conception?

• Male reproductive issues

• STI

• Metritis/endometritis

• Freemartinism

What causes freemartinism in cows?

When a female calf is born twin to a male calf, testosterone from the developing male has a negative impact on the female’s reproductive system leading to 85-95% of female calves being infertile.

Gestation length

• 9 months (282 days)

• Average 279-290 days

Cow placentation

Cotyledonary

Pregnancy diagnostics

• Cessation of estrus

• Ultrasound

• Progesterone

• PSPB (Pregnancy specific protein B)

• Rectal palpation

• Abdominal enlargement

• Fetal movement

• Ballottement

• Mammary development

Progesterone pregnancy detection

• Blood, milk

• 21-24 days

PSPB (Pregnancy specific protein B) pregnancy detection

• Blood sample (Serum or plasma)

• Produced by placenta

• 29 days to reach detectable level

Pregnancy detection with rectal palpation

• 35 days - 150/170 days

• Palpate uterus through rectal walls:

  • 3 “slips”

  • Palpate fetus (65-70 days)

  • Palpate placentome (80-90 days)

What can cause early embryonic death/abortion?

• Lack of nutrition to dam

• Toxins (mold in feed)

• Congenital defects (1st, early 2nd trimester)

• Viral/bacterial infections (Brucellosis, IBR): 5.5-7.5 months of gestation

What is the difference between early embryonic death and abortion

Early embryonic death occurs before skeleton is calcifies, abortion occurs after calcification

Signs of impending calving

• Prominent, swollen vulva ± clear discharge

• Milk drip

• ± decreased appetite

• Restless

• Increased urination

• Isolation

Stage 1 of parturition

• 6-24 hours

• Ferguson reflex

What is the Ferguson reflex?

• Cyclic mechanism causing neural response to release oxytocin

• When lumen of cervix begins to dilate, neural response releases oxytocin to create positive feedback on cervix to increase dilation

Stage 2 of parturition

• 2-12 hours

• Rupture of chorioallantoic membrane

• Release of oxytocin and PGF2 alpha

• Abdominal contractions

• Delivery of calf within 1h in multiparous cows, 1.5h in primiparous cows

Stage 3 of parturition

• Pass placenta in 6 hours on average

• Lasts 3 days - weeks

• Myometrial contractions up to 3 days to return uterus to normal size

• Minor contractions for several weeks

Dystocia in cows

• Prolongation of stage 2

• Causes:

  • Fetal size

  • Fetal position

  • Dam’s pelvic size

  • Uterine inertia

  • Uterine torsion

• Examine cervix 2x, 30 minutes apart for dilation

How is dystocia in cows treated?

• Reposition fetus

• C-section

• Calving chain/jack

Post-Partum issues

• Milk fever

• Prolapsed vagina

• Uterine prolapse

How is milk fever treated in cows

• IV calcium (recover in 10-15 minutes)

• Jugular or udder vein

Prolapsed vagina

Due to stretched uterine ligaments

Uterine prolaspe

• Due to severely stretched/broken ligaments

• Entire uterus pushed out of body

• Must be replaced very quickly to prevent blood pooling and necrosis

• Vulva pinned/sewed shut to prevent recurrence