Seasonality of reproduction in sheep
Zeleke Mekuriaw
EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training on Reproduction
in Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

Introduction
• Sheep in general are considered to be seasonal breeders
• Seasonality more pronounced in feral sheep
• Getting diminished in sheep kept under intensive management
• Photoperiod is a major cause of seasonality of reproduction
sheep in temperate areas
• Other factors such as environmental temperature, feed
availability, social cues have effect on reproductive functions

Economic importance of seasonality of reproduction
Positive:
• Improved survival of lambs
Negative:
• Limits year round availability of lambs
• Prolongs lambing interval
• Prolongs age at first mating/lambing
• Reduces life time productivity

What induces seasonality of reproduction in sheep?
Photoperiod:
• Important in temperate areas
• Less important in tropics
Pineal gland:
• Transducer of photo stimuli to hormone
• Located in the brain
• It is a signal for season change

Photoperiod…
Melatonin:
• Produced during dark hours of a day
• Induces seasonality of reproduction in sheep
• Affects both male and female reproduction
• More potent in female
• Long duration of melatonin secretion is stimulatory
• Short duration is inhibitory
• Melatonin is a signal to the neural structures controlling the
secretion of GnRH

What induces seasonality of reproduction in tropical
sheep?
Feed availability:
• Availability of feed is seasonal in extensive management
system
• More feed during rainy season
• Sever shortage during dry season
• Poor quality during dry season
• Very poor body condition of ewes during dry season
• Most of the mating occur during rainy season (short and long
rainy seasons)

Consequences of poor feeding management
Female:
Long term
• under feeding at early age has carryover effect at later stage
• Affects ovulation rate and twining
• Irreversible effect
Short term effects
• Poor body condition
• inhibition of ovarian activity
• Embryonic mortality
• Silent heat

Consequences of poor feeding management …
Male:
• Reduction in testicular size
• Low semen volume
• Reduced libido
• Higher percentage of abnormal/dead
spermatozoa

Consequences of poor feeding management …
 Measures to be taken:
– Provision of adequate quality and quantity of feed year
round
– Supplementary feeding management for breeding stock
– Strategic feeding (flushing) prior to mating
– Periodic deworming

Ambient temperature
High ambient temperature
• Not significant for indigenous breeds
• May affect imported exotic breeds
Female
– embryonic mortality
– Short duration of heat
– Silent heat
– Prolonged oestrous cycle

Ambient temperature…
Male
• More effect on quality of semen
– Reduced volume of semen
– Higher percentage of abnormal spermatozoa
– Higher percentage of dead spermatozoa
• Effect on libido
– Increased testicular temperature
– More sever in over conditioned rams

Ambient temperature…
Measures to be taken:
• Selection of adaptive breeds
• Provision of suitable microclimate
• Availing amble amount of water
• Maintaining normal body condition of breeding stock

Social cues
Female:
• Introduction of rams to ewes provoke ovarian activity
• Ewes display signs of heat in the presence of rams
Male:
• Presence of female in heat provokes libido in male
• Improves semen volume and quality for AI
• Effect of early isolation of lambs from females on its sexual
activity at later age is not significant

Mating/lambing pattern of Ethiopian sheep breeds
• Literature is very scanty
• Few findings indicate more mating during rainy
season (short and long rainy seasons)
• Lambing often occurs during or the end of main rainy
season

Some information on reproductive performance of Ethiopian
sheep breeds
Age at 1st lambing and lambing interval

Some information on reproductive performance of Ethiopian
sheep breeds
Litter size

Some information on reproductive performance of Ethiopian sheep
breeds
BW, Wt & ADG

Some information on reproductive performance of Ethiopian
sheep breeds
Pre-weaning mortality

Sheep breeds and their distribution

Gaps to be filled!
Conditions Reproductive performance Growth
performance
Improved feeding ? ?
Improved health care ? ?
Housing ? ?
Response to reproductive
technologies
? ?

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