Reproductive traits in sheep and cyclic ovarian activity

Mourad Rekik

EIAR-DBARC-ICARDA-ILRI (LIVES)-FAO Training on Reproduction in Sheep and Goat, Debre Berhan,

Ethiopia, 13-15 October 2014

Synopsis

Introduction

Anatomy revisited

Basic reproductive characteristics

Seasonal reproductive activity

Seasonal reproductive activity: differential traits according

to breed

Hormone relationships throughout the oestrous cycle, waves

of follicular growth

Postpartum anoestrous

Reproduction in young females

Main features of the anatomy of the reproductive tract in ewes and goats

Hymen

Genital tracts

1- Vulva-vagina

2- Uterus

3- Cervix

3- Oviducts

Glands: ovaries

Advanced Duplex(Opossum)

Two UterineHorns

Two Cervices

Two Vaginas

Duplex(Rabbit, Mouse)

Two UterineHorns

Two Cervices

One Vagina

Bicornuate(Pig)

Two UterineHorns (long)

CommonUterine Body

One CervixOne Vagina

Bipartite(Cow, Ewe, Doe)

SmallerUterine Horns

Modified Bipartite(Mare)

Larger UterineBody with SmallerUterine Horns

Simplex(Human)

No UterineHorn, AllUterineBody

Goat

Differential structure of the cervix in ewes and goats

Ewe

Impact on methods of AI in sheep

Type of oestrous cycle, ovulation, length of the cycle (days) and duration of pregnancy (days) in some female mammals

Species Type of cycle Ovulation Cycle length

Pregnancy length

Rabbit Polyoestrus Induced - 28

Cat Polyoestrus Induced - 63

Mare Seasonal

Polyoestrus

Spontaneous 21 350

Cow Polyoestrus Spontaneous 21 282

Ewe Seasonal

Polyoestrus

Spontaneous 16-17 148

Goat Seasonal

Polyoestrus

Spontaneous 21 148

Camel Seasonal

Polyoestrus

induced - 390

Chronology of Pregnancy in Small Ruminants

Entry in the uterus 4 days

Loss of the zona pellucida

7-8 days

Implantation 15-28 days

Organ differentiation

40-60 days

Accelerated fœtal growth

Starting 120 days

Total duration 150 ± 10 days

Sexual traits of the female

Puberty Live weight : 60 % of adult

LW

Age : 6 – 12 months Variation factors: Breed, LW, date of birth

Sexual maturity

Live weight : 75 % of adult LW

Sexual cycle 17 days (3D follicular phase and 14D luteal phase)

Sexual behaviour

Oestrus : 36 hours (24 – 72)In presence of male

Factors of variation : age, season

Ovulation 20 – 40 heures after onset of oestrus

Ovulation rate Breed, season, age, nutrition

Survival of oocytes in the female tract

8 hours (fecundability)

 P

rog

este

ron

e co

nce

ntr

atio

ns

 

 

Oestrus Oestrus Oestrus         

anoestrus 17 D 17 D 17 D 17 D anoestrus

  

Seasonal variation of sexual activity in a non pregnant ewe

Involvement of Photoperiod

Sexual seasonAnœstrus

10

13

16

Photoperiod

(h/D)

SummerSolstic

e Winter

Solstice

Increasing day

length

Long days

Short days

J D J FNOSAJJMAMF

Gonads

Pituitary gland

Hypothalamus

(Pineal gland)

-

+

MelatoninMelatonin

GnRH

FSHLH

Variations saisonières de l'apparition de l'oestrus et de l'ovulation pour des brebis Ile de France

0

20

40

60

80

100

120aout

sept

oct

nov

déc

janv

fév

mars

avril

mai

juin

juil

aout

sept

oct

nov

déc

janv

fév

Mois

% b

reb

is oestrus ovulation

Reproductive seasonality of temperate breeds

0

10

20

30

40

50

60

70

80

90

100

Jul

Aug

Sep

Oct

Nov

Dec

Jan

Feb

Mar

Apr

May

Jun

Month

Barbarine

0102030405060708090

100

Month

Queue fine de l’Ouest

0102030405060708090

100

Jul

Sep Nov Jan

Mar

May

Month

0102030405060708090

100

Jul

Aug

Sep Oct

Nov

Dec Ja

n

Feb

Mar

Apr

May Ju

n

Month

TimahditSardi

WANA breeds: Low reproductive WANA breeds: Low reproductive seasonality (% ewes in oestrus)seasonality (% ewes in oestrus)

0

20

40

60

80

100

120

déc

janv fév

mar

s

avr

mai

juin

juil

aoû

sep

oct

nov

%G

oats

Month

oestrus ovulation

Seasonal variations of oestrus and ovulation in the local Tunisian goat

Lassoued and Rekik, 2005

Equator

Temperate latitudes

Meridional latitudes

Facteur

entraîneur

Facteurs modulateurs

NutritionTemperature

Social interactions

Stress

Photoperiod

Reproductive activity

Variation of reproductive seasonality in sheep and goats

Synchronising

Factor

Modulating

Factors

In hot environments, thermoperiod may affect reproductive performance because heat stress causes large reductions in

fertility mainly due to

Disruptions in spermatogenesis and oocyte development, oocyte maturation, early embryonic development, fetal and placental growth and lactation (Hansen, 2009),

Particularly, in sheep, potentially elevated ambient temperature can impact on the physiological mechanisms regulating follicular development anywhere from primordial follicle through antral formation to ovulatory follicle (Scarammuzzi et al., 1993),

Elevated ambient temperature also can reduce the drive for

sexual behaviour, leading to ‘silent oestrus’. Ovulation was not accompanied by oestrus in 35% of ewes exposed to elevated ambient temperature prior to ovulation, and in those animals displaying oestrus, the period of oestrus was shortened by about half (Sawyer et al., 1979),

The effects of heat stress on the developing follicle reduces the

capacity of the dominant follicle to produce oestradiol and limits oestrous behaviour causing missed reproductive opportunity.

0

20

40

60

80

100

120o

ct

nov

déc

janv fé

v

mar

s

avril

mai

juin

juill

aout

sep

t

oct

nov

déc

janv

% d

ead

SP

Z

MonthSeasonal variations of dead SPZ in the ejaculate of

two Tunisian sheep breeds

Barbarine Noire de Thibar

Waves of Waves of follicular follicular growth growth during the during the ovarian ovarian cyclecycle

0

5

10

15

20

25

30

2 7 12 17 22 27 32 37 42 47 52 57 62 67 72

Duration (days)

Num

ber

of c

ycle

s

Days

Num

ber

of c

ycle

sFrequency distribution of Alpine goats oestrous cycle

according to its length.

Postpartum anoestrus

In average 2 monthsLinked to lactation and sucklingFactors of variation – Breed– Suckling intensity: litter size– Season of birth

Winter-spring: Postpartum anoestrus + Seasonal anoestrus delayed resumption (120 d)

Autumn: earlier resumption (45-60 d)

Specific Reproductive Constraints of Young Females

Low intensity of oestrous behaviour;

Increased sensitivity to seasonal anoestrous;

Low ovulation rate;

Reduced response to the male effect;

High rates of embryo mortality and total reproductive wastage;

Hostile uterine environment.

A higher sensitivity to seasonal anoestrus

0

20

40

60

80

100

120

Jui Aoû Sep Oct Nov Déc Jan Fév Mar Avl Mai Jui Jul

Month

% m

aid

en

ew

es

Ovulation Oestrus

Summer Autumn Winter Spring

• Delayed puberty • Long seasonal anoestrus : 2-6 mois• Pregnancy: 5 months• Postpartum anoestrus: 1-3 months• An inherent low prolificacy

Physiological causes of reduced reproductive efficiency in sheep and goats

In most production systems, sheep and goats give birth once a year, produce single litters and the production is seasonal.

Thank you