Learning Reproduction in Farm Animals

Learning Objective

To understand how environment affects reproduction and how it can be managed.

• Photoperiod
• Long day breeder, horse and wild species.

 
• Short day breeders, Sheep, goats, Deer.

 
• Temperature: both high and low temperatures

Moisiture: - Control nutrients
 

Moderates temperature effects

Photoperiod:

Adapted from Karsch et al. 1984. Rec. Prog. Horm. Res. 40:185

• -Mares:
• ~ 10% nonseasonal
• ~ 80% seasonal
• 2-3 to 30-40 day cycles as mare is coming into season.

 
 
 

 

• Cycle stabilizes at ~21 days.
• ~10% seasonal and erratic.

 Hasten onset of breeding season by increasing photoperiod to 14-16 hours.
 
Effect of Season

Photoperiod

Hormone Alterations

Regumate Information

Pineal Control

Regulation of Seasonality by Light

Regulation of Seasonality by Light

2.

3.

4.

5.

6.
 

Seasonal Control of Reproduction in the Ewe

Graph showing Seasonal Control

Role of Pineal in Control of Seasonal Breeding in Sheep
 

Three Methods to Control Out of Season Breeding

    I.  Control Photoperiod

  II.   Hormone Induction

  III.  Melatonin Stimulation
 

Effect of Light Control

Out of Season Breeding (Hormone Induction)

1. Progesterone and PMSG or P.G. 600

 
1. Implant Norgestomet implant (via ear) for 9 days

 
2. Inject ewes I.M. with PMSG (500 IU) or P.G. 600 at time of implant removal.

 
 
2. Melatonin
1. Implants of Melatonin placed subcutaneously in the ear will provide continuous levels for 1 month
2. Ewes cycle earlier and breeding season will also be longer

 

Temperature Effects on Female:

Heat important when affects body temperature - Sources, both body and environment.
• Effect oocyte cause polyploidy
• Cause early embryonic mortality
• Intensity of estrus may be reduced
• One mechanism, stress causes high glucocorticoids which inhibit LH release

 
Low temperatures - Reduce intensity of estrus

How to manage heat

Facilitate animal thermoregulation

• Environmental control
• Sprinklers for evaporative cooling, except where humidity is high.

 
• Shade, fans
• Breed before hot seasons
• Use artificial insemination to avoid reductions in bull fertility.

 

 

Learning Objectives

To understand how the enviroment influences breeding capacity of males.

1. Photoperiod
2. Temperature
3. Humidity or moisture

1. Short day breeders
2. Hormone Levels

 
Testicular tone:

Seconday sex characteristics:
 
 

 

3. Long day breeders:
 
Mounting Behavior and Reaction Time

Effect of Day Length on Semen Quality

Endocrine influence - Low LH and testosterone Oct. to Feb.

Illustrated Notes

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