Effect of Oestrus Synchronisation and Body Condition on Reproduction
of Anoestrous Ouled Djellal Ewes
The objective of this study was to determine the effects
of progestagen treatment administrated alone or coupled to an injection
of eCG to synchronize oestrus on sheep reproductive traits during the
anoestrus season under extensive management conditions of Algeria. Two
flocks differing by level of body condition score were used. Fertility
rates of treated groups, when compared to control groups, were higher
for ewes matted at lean body condition (0.45-0.47 versus 0.10), whereas
ewes matted at moderate body condition recorded higher performance during
first estrus (0.37-0.45 versus 0.10) and comparable fertility rate for
all mating period. Higher prolificacy rates were performed in synchronized
groups of poor body condition (1.38 versus 1.00) when compared to control
group. For moderate body condition flock, if progesterone and eCG treated
ewes performed higher level of litter size than do control ewes (1.54
versus 1.20) for first estrus, prolificacy rate was similar between all
groups for all mating period. Extra lambs weaned were significant for
lean body condition synchronized groups (0.45) and for moderate body condition
progestagen-gonadotropin treated group (0.33). Results indicated that
it is possible to increase extra lambs weaned in anestrous Ouled Djellal
ewes after artificially induced oestrus.
Ouled Djellal (OD) is the predominant sheep breed in Algeria. Breeding season
of OD breed extends from early April to the end of November, with greater concentration
between June and August. Therefore, one of the major constraints to improve
productivity is the weak level of fertility under field conditions during anoestrus
season in early spring, which is the most suitable time for farmers to breed
their flocks (Madani et al., 2001). Starting season
of mating out of season in early spring by synchronization of oestrus procure
many advantages, such as reducing spread of mating, improving reproductive performances,
accelerating lambing programs and producing lambs for winter markets. The response
of the OD sheep breed to different synchronization treatments was not fully
In Mediterranean area, breeds have a short anoestrus during winter and early
spring and within breeds, there is a large variation (Rosa
and Bryant, 2003). Atti et al. (2004) have
noted though in Barbary breed that as the effect of photoperiod on the seasonality
of reproduction is limited, the traditional mating season occur during spring
(April-May). However, for North African breeds Lahlou-Kassi
(1986), noted that 40-60% of ewes have an anoestrous season from February
to April. As this period corresponds to winter drought, feed availability is
mostly reduced. Ewes mainly face seasonal food scarcity by body reserve use
and probably limit or stop their breeding behavior and ovulation under extensive
management. According to Bossis et al. (1999)
negative energy balance before and during mating causes a linear decrease in
the maximum diameter of successive dominant follicles and eventually results
in anoestrus, due to suppressed LH pulse frequency in the final estrus cycle.
According to Forcada and Abecia (2006), although during
anoestrus season nutrition has a smaller influence on sexual activity than on
ovulation rate, nutrition has an important influence on reproductive function,
but the mechanisms by which these influences are mediated are complex and poorly
Among alternatives for controlling reproductive activity in sheep, which efficacy
had been confirmed over time, intravaginally inserted pessaries impregnated
with progestagen utilized alone or associated to an eCG treatment (Kridli
et al., 2006) and used to stimulate and synchronize oestrus. This
study was designed to determine the effect of progestagen administrated alone
or coupled to gonadotropin (eCG) treatment on reproductive performances (fertility
and prolificacy) and weaning rate of adult OD ewes mated at lean or moderate
Body Condition (BC) under extensive management system.
MATERIALS AND METHODS
Location and Animals
Experiments were conducted from January to December 2001 at two farms
of semi arid region in Sétif Province, situated in North Eastern
part of Algeria (36° 09′ North, 05° 26′ East). The
studies used 310 OD multiparous ewes aged 3-5 years that were
non-pregnant and non-lactating. Levels of body condition score (BCS, 0-5
scale) were selected to represent range of BC at early spring in semi
arid highlands, which vary from 1.5-2.5 units. Ewes chosen for the experiment
belonged to two large flocks (500 and 600 ewes), which had comparable
body conditions; however ewes were selected to obtain two contrasting
levels between the two samples. In farm A females (n = 148) were chosen
to have a lean mean BCS (1.84±0.27 units), where ewes in farm B
(n = 162) were chosen to have a moderate mean BCS (2.46±0.21).
Ewes were scored at the insertion and the withdrawal of pessaries, at
the end of mating and then every two months till the weaning. Both samples
were managed to have positive energy balance from the insertion of sponges
to the end of mating. Within each farm ewes were equally and randomly
divided into three groups: control group (C), treated with progestagen
(30 mg FGA-fluorogestone acetate; Synchro-Part®, Ceva Santé
Animale, France) group (P) and treated with progestagen and injected,
after sponge withdrawal, with 400 IU equine Chorionic Gonadotrophin (eCG;
Synchro-Part®, Ceva Santé Animale, France) group (E).
At mid March ewes of the P and E groups were synchronised in oestrus
in both farms, pessaries were withdrawn 12 days later and then ewes of
E group received subcutaneously an injection of 400 UI eCG. For mating
ram-to-ewe ratio was minimized (1:10). Rams were isolated from the ewes
and introduced simultaneously to the different groups after sponge removal.
In order to have comparable positive body reserves dynamic, ewes chosen
for the experiment were managed separately from day one of synchronisation
to the end of mating period in both flocks, to be fed 300 g of barley
grain and grazed resources of cereal fallows. Since, sponges insertion
to the end of mating similar body condition dynamic was recorded between
flocks. Ewes gained 0.46±0.15 units in flock A and 0.52±0.19
unit in flock B. After mating ewes were released to join to common flocks.
Flocks utilised resources of cereal fallows during spring and cereal stubble
during summer, had free access to water and mineral licks. Since, early
autumn flocks received 300 g of barley grain, cereal straws and hay until
For estimating reproductive traits, two dependant variables were recorded.
Fertility (ewes mated that lambed) and prolificacy (lambs born per ewe lambing)
were estimated after lambing. Date of conception in ewes returning to service
was considered as the oestrus date nearest to 150 days before lambing. A ewe
was considered to have been synchronised during the first fertile oestrus if
it came in oestrus within five days of FGA sponges′ removal (Spitzer
and Carpenter, 1981). Reproductive traits were estimated as the proportion
of ewes that conceived and lambed in either two consecutive oestrus cycles between
150 and 172 days following introduction of rams. Later births were considered
unrelated to the effect of hormonal treatments and therefore, they were not
evaluated. Lambs were kept with their dams until the weaning (two months of
age) and had no access to feed other than that offered to dams. For evaluating
productive traits two dependant variables were recorded; lambs survival as a
trait of the ewe (lambs weaned per lambs born) and weaning rate (lambs weaned
per ewe mated) were also recorded.
Body condition score at mating was tested by using the pair wise t-test
with a least square means statement. Least squares procedures were used
to analyze data on ewe fertility, prolificacy, lambs survival and weaning
rate traits. A fertility score of 1 or 0 was allocated to ewes that lambed
or did not lamb. Prolificacy was the number of lambs born per ewe lambing
(1 or 2), lambs survival was alive lambs at birth to weaning age (if alive:
1 and if died: 0) and weaning rate was the number of lambs weaned per
ewe mated (0, 1, 2). Data are expressed as Mean±SE. Differences
between experimental groups were analyzed by one-way Analysis of Variance
(ANOVA). The significant controls of the differences between the groups
were determined by Duncan′s test.
According to Table 1, fertility of ewes in treated
groups was higher (p<0.05) than that observed in control group during
the first fertile estrus and for the all-mating period following ram introduction
to ewes mated at lean BCS. Effect of synchronization on fertility rate
was effective. Among 16 and 17 ewes that lambed respectively in P and
E groups, 70 and 81% conceived during the first fertile oestrus. Prolificacy
was greater (p<0.05) in the P and E groups when compared to control
group. Only single births were observed in the control group. Lambs survival
rate was comparable for all groups. Consequently, productivity was more
affected by fertility and prolificacy rates than by the percentage of
lambs weaned. Both treated groups recorded a significant increase of weaning
rate (lambs weaned per ewe mated) when compared to control group. Extra
lambs weaned were 0.45 lambs per ewe mated.
For the first fertile oestrus, moderate BCS groups receiving progestagen
alone or coupled to an eCG injection achieved comparable fertility rate.
However, control group performed significantly lower fertility rate than
do treated groups. The overall lambing rate (from mating at first fertile
oestrus) was 19/29 (66%) and 24/33 (73%) for respectively P and E groups
(Table 2). Fertility rates for the all-mating period
were comparable for all groups. For the first fertile oestrus prolificacy
rate was higher for synchronized ewes receiving eCG when compared to control
group, where P group recorded a comparable performance to C and E groups.
For the all mating period prolificacy rates were similar between all groups.
Lambs survival rate was high and similar among all groups. Therefore,
weaning rate was only affected by fertility and prolificacy. Group E performed
higher weaning rate when compared to control group, extra lambs weaned
were 0.33, while P group recorded a similar weaning rate when compared
to earlier groups.
||Reproductive performances and weaning rate of synchronized
and mated ewes at lean body condition
|a and b: Means within a row with
different superscripts differ (p<0.05)
||Reproductive performances and weaning rate of synchronized
and mated ewes at moderate body condition
|a, b and c: Means within a row
with different superscripts differ (p<0.05)
The present results show that during anoestrus season progestagen alone
or associated to an injection of 400 IU of eCG after sponge withdrawal
affected reproductive and productivity performances of OD ewes belonging
to both lean and moderate body condition groups, although performances
varied according to level of body condition at mating during the two consecutive
oestrus cycles following ram introduction.
Fertility rates of synchronised groups for the all mating period (45-62%) were
comparable to results described in earlier study for Awassi breed in Jordan
(Alnimer et al., 2005; Kridli
et al., 2006). However, fertility was less than those observed in
Spain by Forcada et al. (1999) for Rasa aragoneza
ewes (76.4-82.8%) and by Todini et al. (2007)
for Sarda ewes (83%). Breed, dose, body condition and overall managerial conditions
may have caused difference.
Level of fertility of synchronised ewes by intravaginal progesterone impregnated
pessaries alone or coupled to gonadotropin administration were higher for ewes
mated at lean BCS (0.45-0.47) than that observed in control group (0.1) and
was in agreement with results reported by Kridli et al.
(2006) for Awassi ewes. Ewes mated at moderate BCS recorded a higher fertility
rate during the first fertile oestrus when compared to control group, but in
the second oestrous period, this difference was not significant (p<0.05).
The lack of significance may be due the reduced reproductive seasonality, which
is probably more modulated in this case by the effect of body condition at mating
on the resumption of cyclic activity of non treated OD ewes.
Administration of progestagen alone or coupled to an eCG injection during the
anoestrus season was effective in oestrus synchronization of OD ewes and confirms
results reported by Kridli et al. (2006) for Awassi
ewes. Using FGA-impregnated intravaginal sponges affected significantly the
fertility of OD ewes mated at lean BCS during the all mating period and moderate
BCS during the first fertile oestrus, while Laliotis et
al. (1997) showed that synchronization during anoestrous period without
gonadotropin (eCG) administration had been ineffective. Within flock, ewes yielded
similar fertility rates regardless of treatment, indicating that FGA-impregnated
sponges utilized alone or associated to gonadotropin treatment was likewise
effective at inducing follicular development during anoestrus, which is in agreement
with results of Kridli et al. (2006). However,
Zaiem et al. (1996) found that ewes receiving
FGA and eCG had higher fertility rates (81.2-84.3%) when compared to FGA-treated
ewes receiving no gonadotropin (57.5%). Discrepancy between the results obtained
in the current study and those reported by the literature my be due to breed,
time of eCG injection relative to sponge withdrawal, dose of eCG and routes
of administration. According to Wildeus (2000), fertility
vary greatly (27-83%) when intravaginal sponges are applied, dependent on breed,
co-treatment, dose, management and mating system.
Nutrition is one of the main factors affecting ovulation rate (Forcada
and Abecia, 2006). Fertility rates of moderate BCS groups were comparable
(0.46-0.62), emphasizing that body condition at mating and treatment effects
were likewise effective at inducing cyclic estrus. Fertility rate of control
group of moderate BCS at mating (0.46) was close to performance of treated groups
of lean BCS (0.45-0.47), confirming an efficient effect of body reserves at
mating on reproduction performances. According to Forcada
and Abecia (2006), high fat and food intake are able to modify the sensitivity
of the hypothalamus to oestradiol negative feed back during seasonal anoestrus,
with those effects being associated to a reduced amount of NPY mRNA and to an
increase of plasma insulin, glucose and leptin concentrations.
Equine chorionic gonadotropin use in sheep estrus induction and synchronization
programs is well established to improve follicular development, multiple births
and conception rate (Cunningham et al., 1980).
For ewes mated at moderate or lean BCS, the mean litter size of E groups was
similar to that of P groups, indicating no positive effect of eCG on prolificacy.
These results agreed, with the findings of Kridli et al.
(2006). For flock B prolificacy was comparable between all groups for all
the mating period, although E group recorded higher level of prolificacy for
the first fertile oestrus when compared to C group. Probably eCG effect on prolificacy
was more effective during only the first oestrus. For ewes mated at lean BCS,
P and E groups yielded similar litter size, which was significantly higher than
that of control group and contrast with the findings of Kridli
et al. (2006). Difference between flocks indicated that progestagen
treatment alone or coupled to eCG increased significantly litter size of only
lean BCS ewes at mating. Probably interactions exist between body condition,
body condition gain at mating and effects of eCG on ovulation rate and liter
size for OD breed. According to Forcada and Abecia (2006)
during anoestrous season nutrition is one of the main factors affecting reproduction
and has more influence on ovulation rate than on sexual activity.
Synchronization improved the production of OD ewes mated during anoestrus season.
However, results are different when either type of treatment or BCS at mating
are considered. Synchronization improved significantly reproductive efficiency,
although extra lambs weaned varied from 0.13-0.45 per ewe treated. Improvement
is similar to that previously reported for Spanish Rasa Aragonesa breed treated
with Melatonin on March (Forcada et al., 2002).
For lean BCS ewes, extra lambs weaned per ewe mated were higher for synchronized
groups (0.45) than control group. For moderate BCS flock, significant more lambs
per litter (0.33) were recorded in E group when compared to non-treated group,
while P and C groups recorded a comparable performance. For flock A and E group
of flock B differences can be associated with a significant increase in fertility
and prolificacy. Superiority of FGA-eCG ewes mated at moderate BCS may be due
to the combination of better nutritional condition at mating and eCG effect
on litter size. Within flock, differences between treated and control groups
for respectively fertility (0.35-0.37) and extra lambs weaned per ewe mated
(0.45) were more pronounced in treated groups with low BCS when compared to
equivalent groups mated at moderate BCS (fertility: 0.11-0.16; extra lambs weaned:
0.13-0.33). Although dynamic of body condition during mating was quite similar,
these results suggest that there were different responses of reproduction to
level of BC at mating. Fertility and productivity rates of treated groups were
the highest for moderate BC at mating, while effect of flushing on reproduction
in treated groups of lean BCS was the most efficient. According to Bocquier
et al. (1993) in a study with Prealpes ewes, the effect of body condition
gain was stronger than the effect of BC (static), but both were confounded in
a static-dynamic effect.
These data demonstrated that both BC and synchronisation could have an
important influence on the response of anoestrus OD ewes to out-of-season
breeding with hormones in extensive management systems of semi arid region
of Algeria. Synchronization of ewes can be successfully applied to improve
productivity. The combination of nutrition management to controlled breeding
techniques, such as oestrus synchronization, would benefit an intensive
breeding program of OD breed.
This study was supported by grant No. (F 1608/04/2000) of the National
Institute of Agricultural Research (INRAA). The authors gratefully acknowledge
also the assistance of the personnel at farms of Khababa and Makhloufi.
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