Seasonality of reproduction in sheep

Presented by Zeleke Mekuriaw at the EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training Workshop on Reproduction in Sheep and Goat, Debre Berhan, Ethiopia, 13-15 October 2014

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

2. 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

3. 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

4. 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

5. 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

6. 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)

7. 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

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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

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

16. Some information on reproductive performance of Ethiopian sheep breeds Litter size

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

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

19. Sheep breeds and their distribution

20. Gaps to be filled! Conditions Reproductive performance Growth performance Improved feeding ? ? Improved health care ? ? Housing ? ? Response to reproductive technologies ? ? Full Information on breeds’ performance!!