Learning Reproduction in Farm Animals

Learning Objectives:

To understand what happens to cause parturition and what happens during and after parturition.
To understand the hormonal control of parturition.
To understand retained placentas, artificial induction of parturition and uterine involution.
 

Skunk Cabbage -
 
 

Gene Defect -

Steps
• ­ Fetal ACTH causes -
• ­ Fetal Corticosteroids causes -
• ¯ Progesterone levels

(¯ placental production or CL regression) -
• ­ Production of Estrogens by placenta -
• ­ PGF_2a production by uterus -

Hormonal changes cause:

1.

2.

3.

4.

5.

6.

Significance of initial hormonal changes.

¯Progesteorne - removes block on uterine contractions.
 

­ Estrogen - makes uterus more responsive to induction of contractions i.e., more irritable and ­ smooth muscle tissue stimulation.
 

Events just Prior to Parturition:

1. Pelvic ligaments soften - Tail head sinks due to ­ estrogens and relaxin.

 
 
2. Cervix softens and begins secreting stringy mucus - ­ estrogens and relaxin.

 
 
 
3. Swelling of vulva.

 

 

4. Udder swells - fills with first milk and due to edema:

 
 
 
5. Fetus moves into proper position - resting on thorax, front feet and head facing the cervix.

 

 
 
 

• Dialation of Cervix. (2-6 hours, cow)

 
• Uterine contractions become coordinated and regular - (estrogen & PGF2a induced).

 

 

• Fetus pushed against cervix - amnion dialates cervix.

 

 

• Allanto-chorion may break.

 

 
   
• Expulsion of Fetus (.5-2 hours, cow)

 

• Strong uterine contractions due to synergistic actions of high estrogen, PGF2a and oxytocin.

 
• Strong abdominal muscle contractions.

 
• Amnion ruptures - mucin lubricates vagina - vestibule

 
• Fetus passes through vagina - vestibule.

 


 
 

Length of Stage II

 
 
• Expulsion of the Placenta. (4-5 hours, cow)
• Uterine contractions continue.
• Blood forced from cotyledon villi - shrinkage separates cotyledon and caruncle.
• Contractions push placenta out.

 
Causes of retained Placentas:
• -Infections caused adhesions between cytoledon and caruncle.
• -Calving stress - twins or calving difficulty - edema of cotyledon - won't separate from caruncle.
• -Weak uterine contractions - villi won't shrink.

• Do not manually remove from uterus; uterine damage greater than infection of retained placenta.

 

 
 
 

• Infuse uterus with tetracycline and systemic injections of penicillin until placenta passes ~ 2-4 days.

 

 
 

• Vaccinate for Brucellosis and leptospirosis.

 
• Make sure Vitamin A, E and Selinium are not difficient in diet.

 
• Don't have cows overconditioned at calving.

 
• Have sanitary calving conditions.

 
• Allow heifers to be large enough at calving and don't breed to bull that sires larger calves than your female can handle.

 

 

• Cow passes lochia - 1 to 2 weeks after birth. (mucus, blood, fetal membranes and surface of caruncle).

 
• Caruncle regenerated by ~ 30 days post calving.

 
• Uterus completely involuted by 45 days postpartum.

 
• Shrinking of uterus due to muscle contractions.

 
• Involution enhanced by: suckling _ oxytocin release by estrus periods - estrogen.

 
• Foal heat 10-15 days postpartum in mare has low fertility due to lack of involution.

 
 
 

Reasons:
Time parturition to ¯ labor costs

Avoid dystocia (Large Fetus)
 

How to do it:
 
Give ACTH

Give Corticosteroids. (Dexamethasone)

Give PGF_2a

Give Oxytocin

.

Cow
 
- do not induce before last 2 weeks of gestation.
 
Method:
Dexamethasone - parturition in 48 hours, 20-50 mg/IM
 
 

 
 

-High incidence of retained placentas and lower postpartum fertility.
 
 
 
Prostaglandins -
 
 
 
 
Sheep - Best within a few days of parturition
 
Dexamethasone (8-20 mg) Parturition in 24-72 hours.
 
 
 
 
Goat - CL is most important throughout pregnancy
 
 
 
 
Sow - Do after day 111 of gestation
 
PGF_2a (10 mg/IM) parturition in 29-48 hours.
 
 
 
 
 
 

 
 

Mare - Do after day 320 of gestation.
 
Oxytocin (20-60 I.U.) close to term.
 
 
 
 
 
 
 
 
 

 

Bitch -
 
 

• All females in a feedlot should be examined rectally for pregnancy, and abortion induced at that time.
• Animal induced to abort should be in good health and well adjusted to the feedlot.
• One should always remember, abortion will be stressful and combined with any other stress (diseases like shipping fever, pneumia, etc.) can cause extreme losses in gain efficiency or even death.
• Growth promotants containing progesterone or analogues to progesterone may interfere with induction of abortion and should be withheld until after abortion occurs.

1. Heifers that are less than 150 days into gestation can be aborted with a single intramuscular injection of 25 mg Lutalyse or 500 mg Estrumate. Efficiency of 90%.
2. After 150 days of gestation, combination of 25 mg Dexamethazone and 500 mg Estrumate is needed to cause abortion. Efficiency of 95%.
3. Abortion will occur over 2 to 10 days.
4. All abortions should be recorded, and heifers which fail to abort re-examined.
5. Failure to induce abortion is most likely caused by failure of luteolysis. Re-treatment will usually cause abortion.
6. In the case of fetal mummification, Prostaglandin treatment will stimulate expulsion.
7. Cows over 4 months pregnant will have a high percent of retained placenta (80%). Most cases will resolve themselves, but the producer needs to monitor health of females after abortion.

Illustrated Notes

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