https://doi.org/10.52973/rcfcv-e33275
Received: 30/05/2023 Accepted: 26/07/2023 Published: 08/08/2023
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Revista Científica, FCV-LUZ / Vol. XXXIII, rcfcv-e33275, 1 – 7
ABSTRACT
This study aimed to determine the ecacy of post mating human
Chorionic Gonadotropin (hCG) during anestrus on the formation of
the accessory corpus luteum and some reproductive parameters. For
this purpose. after synchronization of all the animal were divided into
group 1 (n=100), group 2 (n=100), and group 3 (n=100) by applying 600
IU of hCG 6 d after sponge removal, 600 IU of hCG 8 d after sponge
removal, and no hCG application (Control), respectively. The difference
between groups in terms of reproductive parameters such as estrus,
pregnancy, multiple pregnancy, litter size, and productivity was not
statistically signicant. The live birth weight of lambs was evaluated
for singletons, twins, and triplets. The difference between group 1
and the control group was statistically signicant in singleton lambs
(P=0.04). The difference between group 1 and control (P<0.001) and
between group 2 and control (P<0.001) was statistically signicant for
twins. In triplets, group 1 was different from both groups (P<0.001) and
group 2 was different from the control group (P<0.001). In addition,
when the placenta weight and the daily body weight gain of singleton
lamb in the neonatal stage were examined, the values of both groups
that were administered with post mating hCG were higher than the
control group (P<0.001). The Progesterone (P
4
) level in blood samples
taken on the 21
st
d of pregnancy was found to be different between
all groups. Furthermore, P
4
levels were found to be higher in group
1 compared to the other two groups (P<0.001). In the light of these
ndings, it was determined that hCG administration after mating
contributed to placenta and offspring development by elevating P
4
levels. It was concluded that hCG should be administered 6 d after
the sponge will be removed (on d 5 postmating) for optimal ecacy.
Key words: Anestrus; postmating; Kangal; sheep; progesterone;
reproduction
RESUMEN
Este estudio tuvo como objetivo determinar la eficacia de
los tratamientos con gonadotropina coriónica humana (hCG)
posemparejamiento durante el anestro sobre la formación del cuerpo
lúteo accesorio y algunos parámetros reproductivos. Para ello, después
de la sincronización de todos los animales se dividieron en grupo 1
(n=100), grupo 2 (n=100) y grupo 3 (n=100) mediante la aplicación de
600 UI de hCG 6 d después de la eliminación de la esponja, 600UI
de hCG 8 d después de retirar la esponja y sin aplicación de hCG
(Control), respectivamente. La diferencia entre grupos en términos de
parámetros reproductivos como celo, preñez, preñez múltiple, tamaño
de la camada y productividad no fue estadísticamente signicativa.
Se evaluó el peso vivo al nacer de los corderos para los únicos,
mellizos y trillizos. La diferencia entre el grupo 1 y el grupo control fue
estadísticamente signicativa en los corderos únicos (P=0,04). La
diferencia entre el grupo 1 y el control (P<0,001) y entre el grupo 2 y el
control (P<0,001) fue estadísticamente signicativa para los gemelos.
En los trillizos, el grupo 1 fue diferente de ambos grupos (P<0,001) y el
grupo 2 fue diferente del grupo control (P<0,001). Además, cuando se
examinaron el peso de la placenta y la ganancia diaria de peso corporal
de corderos únicos en la etapa neonatal, los valores de ambos grupos
que recibieron hCG posemparejamiento fueron más altos que el grupo
control (P<0.001). Se encontró que el nivel de progesterona (P
4
) en las
muestras de sangre tomadas el d 21 the preñez era diferente entre
todos los grupos. Además, se encontró que los niveles de P
4
eran más
altos en el grupo 1 en comparación con los otros dos grupos (P<0,001).
A la luz de estos hallazgos, se determinó que la administración de hCG
después del apareamiento contribuía al desarrollo de la placenta y la
descendencia al elevar los niveles de progesterona. Se concluyó que
la hCG debe administrarse 6 d después de retirar la esponja (el d 5
después del apareamiento) para una ecacia óptima.
Palabras clave: Anestro; apareamientos; Kangal; ovejas;
progesterona; reproducción
Determination of the ecacy of human Chorionic Gonadotropin (hCG)
administrations on reproductive performance, placentation, parturition,
and neonatal parameters on different post–mating days in Kangal ewes
sexually induced during anestrus
Determinación de la ecacia de la administración de Gonadotropina Corionica humana (hCG) sobre
el desempeño reproductivo, la placentación, el parto y los parámetros neonatales en diferentes días
posteriores al apareamiento en ovejas Kangal inducidas sexualmente durante el anestro
Abdurrahman Takci* , Mehmet Bugra Kivrak
Sivas Cumhuriyet University, Faculty of Veterinary Medicine, Department of Obstetrics and Gyneacology. Sivas, Turkey.
*Corresponding author: abdurrahmantakci@cumhuriyet.edu.tr
Efficacy of hCG in reproductive parameters in Kangal ewes / Takci and Kivrak _____________________________________________________
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INTRODUCTION
Nowadays, embryonic loss is a major obstacle to livestock
reproductive efficiency. In the 3–week period following fertile
matings, sheep (Ovis aries) and goats (Capra hircus) experience
30–40% embryonic loss, and 70–80% of these preimplantation losses
occur between 8–16 d following mating [1]. The primary cause of this
condition is insucient luteal function, which requires Progesterone
(P
4
) supplements early in pregnancy to prevent it. The increase in P
4
levels improves pregnancy rates and contributes to fetal development
[1, 2, 3, 4, 5]. In addition to these factors, the seasonal dependence
of sheep reproduction limits reproductive effectiveness. The
investigation of the reproductive physiology of sheep has revealed that
follicular dynamics persist during anestrus. Accordingly, interventions
on ovulation can induce fertile estrus and ovulation at any time of
the year, resulting in pregnancies [6]. However, during anestrus
stimulation, luteal P
4
secretion is suppressed because ovulation
and total luteal volume are lower compared to the breeding season.
This reduction is further compounded by a decline in Gonadotropin
support. Therefore, there is a greater need for direct P
4
supplements
or interventions to increase Progesterone secretion during sexual
stimulation in anestrus [6].
The exogenous administration of Gonadotropin–releasing hormone
(GnRH) and human Chorionic Gonadotrophin (hCG) to sheep and
cattle (Bos taurus) have the same goal. The purpose of using GnRH
or hCG is to induce ovulation in the dominant follicle [7, 8, 9]. In
sheep synchronizations, hCG applications are usually performed
after the termination of P
4
applications. It is known that GnRH and
hCG administered during this period do not cause a significant
increase in reproductive efficiency [10, 11]. However, when this
hormonal treatment is delayed until after mating, it can stimulate
the formation of the accessory corpus luteum (CL) by inducing
ovulation in the dominant follicle of the rst wave of the following
cycle. Therefore, this favorable situation results in increased plasma
P
4
concentration. Increased P
4
levels during the maternal acceptance
phase of pregnancy improve reproductive eciency [5, 8, 12]. Post
mating hCG administration increases P
4
levels, which signicantly
strengthens placentation during embryonic and fetal stages [13].
In the light of this information, the aim of the present study was to
improve the function of the CL in the current pregnancy by increasing
the accessory CL or luteinizing effect by ovulating the dominant
follicle of the rst follicle wave that develops after mating. On different
postmating d, the ecacy of hCG administration on reproductive
performance, placentation, and various parturition and neonatal
stage parameters was determined.
MATERIAL AND METHODS
Location
The study was carried out at a sheep farm in Ortaklar Village, Yıldızeli
District, Sivas Province, Turkey with coordinates 39°50'1" | 36°20'49",
and an altitude of 1,290 meter above sea level. Its pasture is located
in a geography dominated by steppe between high mountains.
Animals and treatment schedule
Before starting the study, 400 ewes and 40 rams that met the
inclusion criteria were screened for general health. From these
animals, 300 ewes and 30 rams of similar age and condition were
selected for the study.
This study was carried out with 300 ewes (3–5 years old) that were
conceived in the fall, gave birth in the spring, and nursed their lambs
for approximately 50–70 d during the early anestrus period (April).
At the beginning of the application, the average body weight of the
animals was 44 ± 5 kg and the body condition score (BCS) were in the
range of 2.5–3.25. Simultaneously, since the study was carried out
during anestrus, 30 Kangal rams aged 4–6 years with proven fertility,
weighing (Pinar, PR–110, Türkiye) 102 ± 8 kg and having a BCS of 3–5
were used to perform mating during sexual stimulation.
When the records of the establishment were examined, it was
determined that although the sheep were housed with the rams during
the anestrus period in previous years, no pregnancy occurred during
this period. Therefore, P
4
levels were measured in blood samples
collected prior to application. Examining the P
4
levels revealed that
neither the study nor the control groups found any sheep with P
4
values at luteal and above (≥1 ng·mL
-1
), and the P
4
values of animals
in all groups were at sub–basal levels (<1 ng·mL
-1
).
Animals were divided into 3 groups, each containing 100 sheep.
On d 0, a vaginal sponge containing P
4
hormone (a white, 40 × 30mm
cylindrical polyurethane sponge containing 20 mg Chronolone
ugestone acetate; Chronogest® CR, MSD, Turkey) was inserted in
all groups. Seven d after this application (d 7), the inserted vaginal
sponges were removed and PGF
2
α hormone (263 µg Cloprostenol
sodium equivalent to 250 µg Cloprostenol per ml; PGS®, Alke, Turkey)
was applied. While the vaginal sponge was removed and PGF
2
α hormone
was administered, 480 IU of equine chorionic gonadotrophin (each mL
of solution for injection contains 240 IU of Gonadotropin hormone;
Chronogest/PMSG®, MSD, Turkey) was injected simultaneously. Rams
were introduced one d later (d 8), and ewes were kept with rams for 5 d
(until d 13). Mating animals were considered to be in estrus. Matings were
done by natural insemination. Mated animals were considered estrus
positive. 600 IU of hCG hormone (containing hCG at a concentration
of 300 IU per mL when lyophilized solution powder was mixed with
solvent; Chorulon® CR, MSD, Turkey) was administered to animals in
group 1 on d 13 (6 d after removal of vaginal sponges) and to animals in
group 2 on d 15 (8 d after removal of vaginal sponges), as for group 3
(control) sheep received no treatment. In all groups, animals showing
estrus mated at 31 ± 3.2 h after PGF
2
α hormone. There was no statistical
difference between the groups.
Pregnancy examination
Two pregnancy examinations were performed: the rst using the
transrectal ultrasonographic method (Mindray DP50/Vet/US, Türkiye)
22 d after the introduction of rams (d 30) and the second by using the
transabdominal ultrasonographic (Mindray DP50/Vet/US, Türkiye)
method on d 68. All Pregnancy examinations were performed rectally
in the supine position with a B–mode, linear array 5.0–7.5 MHz rectal
probe ultrasonography device (Mindray DP50/Vet/US, Türkiye) to
determine early pregnancies and litter counts, or transabdominally
to determine embryonic and fetal losses that may occur in the following
d of pregnancy. For transabdominal examination, the hairless area
just above the breast, ventral to the right fasting pit, was preferred for
probe insertion. The dorso–caudal aspect of the breast was scanned
completely according to whether pregnancy–related ndings could be
obtained in this area. According to the stage of pregnancy detected
in the ultrasonic examination, after the detection of the gestational
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sac, it was decided that the animal was pregnant with the detection
of the embryo or fetus, offspring membranes, fluids, heartbeat,
and placentomes. The establishment was visited at certain periods
(monthly) to follow up on the pregnancies. One week before the probable
birth date, daily visits were made, and birth records were kept.
Housing and nutrition
Approximately two months before the start of the study, the rams
were separated from the ewes in wooden pens in the same pen. However,
this separation was not sucient to block the pheromone. From the
beginning of the application until the rst pregnancy examination, the
animals in all groups spent 6 h·d
-1
in the newly awakened pasture and
spent the rest of the time in the facility with a ration of 750 g meadow
grass (Poa annulaL.), 750 g wheat straw (Triticum aestivumL.), 500 g
alfalfa grass (Medicago sativa L), and 250 g barley grits (Hordeum vulgare
L.) per animal per d. After the rst pregnancy examination, the animals
spent the entire d grazing in the pasture.
After birth, the lambs were kept together with the mother in the
paddocks, where only the pups could pass through and be fed ad libitum
for a period of 1 week to 1 month. Water, dry alfalfa (Medicago sativa L),
and commercial lamb starter feed were kept ad libitum in the section
where only the lambs could enter and exit.
Collection and evaluation of blood samples
Samples for the rst blood examination were taken from animals
in all groups 1 week before the start of the study. The second blood
samples were taken during the rst pregnancy examination, 22d
after ram introduction (d 30). In order to determine the P
4
level, 10
mL of blood samples taken from the vena jugularis were kept at room
temperature for half an h. The blood samples were then centrifuged in
a refrigerated centrifuge (Nüve NF 800, Nüve Laboratory & Sterilization
Technology, Türkiye) at 4,000 g/5min, and two 1 mL samples were
taken into microcentrifuge tubes (Eppendorf, Hamburg, Germany)
and stored at -80°C(Haier, DW–86L828S, China) until the time of
measurement. P
4
measurement was made with chemiluminescence
microparticle immunoassay [9] using the ARCHITECT Progesterone
Chemiluminescence (7K77) Abbott test kit and a fully automated
ARCHITECT –i2000SR instrument (Abbott Diagnostics, AbbottPark,
USA) with an analytical sensitivity of ≤ 0.1ng·mL
-1
and a measuring
range of 0.1–36.0 ng·mL
-1
. The intra–assay coecient of variation
ranged between 3.4–5.5% and 1.6–2.2% for low– and high–level P
4
concentrations respectively. Analyses were validated for serum (in
serum and blood collected in serum separator tubes) and plasma (with
Na heparin, Li heparin, and K
++
–Ethylene diamine tetra acetic acid
(EDTA) anticoagulants) samples. Validation was not performed with
anticoagulants other than those mentioned.
Estrus rate
Number of animals showing estrus in the group/total number of
animals in the group
Pregnancy rate
Number of pregnant animals in the group/total number of animals
in the group
Multiple pregnancy rate
Number of animals with multiple pregnancies in the group/total
number of pregnant animals in the group
Embryonic–fetal mortality
Number of embryonic–fetal deaths in the group /total number of
pregnant animals in the group
Number of births
Number of pregnant animals that completed pregnancy and gave birth
Number of offspring
Number of offspring born from the number of pregnant animals
Productivity
Total number of offspring/total number of pregnant animals
Lamb weight
Lamb weight was measured (Pinar, PR–110, Türkiye) half an h (30 in)
after birth to allow for their mothers to dry them. Measurements were
made at the end of this period.
Live weight at birth
Weight 30 min after birth (after complete drying)
Daily live weight gain in the neonatal stage
(Weight on d 30 − live weight at birth) / 30
Placenta weight
Weight of the placenta after cleansing of the fetal juices
Neonatal mortality
Number of lambs that died in the group between postnatal d 0–30/
total number of lambs born in the group
Dicult birth rate
Number of dicult births in the group /total number of births in
the group
Statistical analysis
Data were analysed using SPSS version 26 (IBM Corp., Armonk, NY,
USA). Reproductive parameters were analysed using the chi–square
test. Lamb parameters and hormonal measurements were analyzed
by one–way ANOVA and post–hoc Duncan’s test, and the results were
expressed as mean ± standard deviation (SD). Progesterone level
determined all the sheep in the groups. But in statistic evaluation
progesterone measurement belongs to non–pregnant sheep have
been excluded. Statistical signicance was set at P<0.05.
RESULTS AND DISCUSSION
After health screening, 300 healthy ewes with sub–basal P
4
levels
were subjected to synchronization. P
4
–impregnated sponges were
kept in the vagina for 7 d and removed completely after 7 d. After
synchronization, estrus was achieved in 79, 81, and 82 sheep in groups 1,
2, and 3, respectively. Two consecutive ultrasonographic examinations
were performed to conrm pregnancy, the rst on d 22 and the second
on d 60 after mating. In the rst pregnancy examination 73, 69, and 70
FIGURE 1. Progesterone level in blood samples taken on the 22
nd
day of pregnancy:
Group 1 median 5.14 (3.78–7.55), group 2 median 4.45 (2.36–5.66), and control
median 4.02 (2.79–4.88)
Efficacy of hCG in reproductive parameters in Kangal ewes / Takci and Kivrak _____________________________________________________
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ewes were pregnant in groups 1, 2, 3, espectively. However, pregnancies
detected at the rst examination but not detected at the second
examination were considered embryonic–fetal losses. There were 2
embryonic–fetal deaths in group 1, 2 in group 2, and 4 in group3. There
were 8, 5, and 4 triplet pregnancies and 32, 28, and 29 twin pregnancies
in groups 1, 2, and 3, respectively. In order to record the births (litter
size, mode of delivery, live birth weight, placenta weight, among others),
we stayed in the facility during the birth period, and all births took
place within 6 d. A total of 119, 104, and 100 lambs were born in 69, 67,
and 69 births in groups 1, 2, and 3, respectively. Of these, 5 in group 1,
2 in group 2, and 3 in group 3 were considered dicult deliveries. At
the 30–d neonatal stage, there were 5 neonatal losses in group 1, 4 in
group 2, and 3 in group 3 (TABLE I).
TABLE I
Reproductive parameters, birth, and neonatal period data of the study
Parameters
Groups (n=100)
Group 1 Group 2 Group 3
Number of Animals in Estrus
79 81 82
Number of Pregnancy
73 69 70
Number of Twin Pregnancies
32 28 29
Number of Triplet Pregnancy
8 5 4
Number of Multiple Pregnancies
40 33 33
Number of Births
69 67 66
Embryonic–Fetal Mortality
2 2 4
Number of Lambs
119 104 101
Reproductivity
119/71 104/67 101/66
Dicult Birth Rate
5/71 2/67 3/66
Neonatal Mortality
5/119 4/104 3/101
TABLE II
Estrus rates and statistical evaluation of the study groups
Estrus Group 1 Group 2 Group 3 Total
Positive
1
79
a
(79%) 81
a
(81%) 82
a
(82%) 242 (80.7%)
Negative
1
21
a
(21%) 19
a
(19%) 18
a
(18%) 58 (19.3%)
Total 100 100 100 300
1
: number of animals and (percentage),
a,b
: varied characters in the same row are
statistically signicantly different (
P<0.05)
TABLE III
Pregnancy rates in the study groups and statistical evaluation of the results
Pregnancy Group 1 Group 2 Group 3 Total
Positive
1
73
a
(73%) 69
a
(69%) 70
a
(70%) 212 (70.7%)
Negative
1
27
a
(27%) 31
a
(31%) 30
a
(30%) 58 (29.3%)
Total 100 100 100 300
1:
number of animals and (percentage),
a,b
: varied characters in the same row are
statistically signicantly different (
P<0.05)
TABLE IV
Twin, triplet, and multiple pregnancy rates and statistical evaluation
Multiple Pregnancy Group 1 Group 2 Group 3 Total
Positive
1
40
a
(73%) 33
a
(69%) 33
a
(70%) 106 (47.7%)
Negative
1
33
a
(45.2%) 36
a
(52.2%) 47
a
(58.8%) 116 (52.3%)
Total 100 100 100 300
1:
number of animals and (percentage),
a,b
: varied characters in the same row are
statistically signicantly different (
P<0.05)
Since the synchronization method was the same in all groups, estrus
rates were similar in all groups (P=0.58) (TABLE II).The embryonic–fetal
mortality rate was not signicantly different between the groups
(P=0.34), and there was no difference in neonatal mortality rates
between the groups (P=0.62).Total pregnancy rates (P=0.8) and
multiple pregnancy rates (P=0.24) were not different between the
groups (TABLE III and TABLE IV respectively).
When P
4
levels were analyzed in blood samples taken during the
rst pregnancy examination on the 22
nd
d of pregnancy, a signicant
difference was found between all groups (P<0.001). As shown in FIG.1,
group 1 had higher P
4
levels compared to both group 2 and group 3,
and group 2 had higher P
4
levels compared to group 3.
All lambs were weighed after birth. Live birth weights were
evaluated separately for singletons, twins, and triplets. For singleton
lambs, live birth weight was signicantly higher in group 1 compared
to group 3 (control) (P=0.04) (FIG.2).
When the live birth weight of twin lambs were compared, there
was a signicant difference between group 1 and group 3 (control)
(P<0.001) and between group 2 and group 3 (control) (P<0.001) (FIG. 3).
When the live birth weights of triplet lambs were compared, a
signicant difference was found between all groups (P<0.001) (FIG. 4).
At the neonatal stage, daily body weight gains were compared
between singleton lambs. When daily body weight gain was higher
in group 1 compared to group 3 (P=0.003), there was no difference
between group 1 and group 2. On the other hand, when daily body weight
gain was higher in group 2 compared to group 3 (P=0.01), there was
no difference between the groups for twin and triplet lambs (FIG. 5).
FIGURE 2. Live birth weight comparison of singleton lambs
FIGURE 3. Live birth weight comparison of twin lambs: P<0.001 between group 1
and control, P<0.001 between group 2 and control; group 1 median 4.49 (3.91–5.12),
group 2 median 4.27 (3.77–4.92), and control median 3.79 (3.03–4.53)
FIGURE 4. Live birth weight comparison of triplet lambs: P<0.001 between all
groups; group 1 median 3.95 (3.52–4.36), group 2 median 3.75 (3.50–4.04), and
control median 3.47 (3.32–4.14)
FIGURE 5. Comparison of daily body weight gain in the neonatal stage for
singleton lambs: Group 1 median 0.26 (0.14–0.51), group 2 median 0.26 (0.14–0.41),
and group 3 (control) median 0.23 (0.15–0.32)
FIGURE 6. Comparison of placenta weights between the groups for singleton lambs
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In the follicular wave dynamics in small ruminants, it is assumed
that the follicle reaches dominance in the rst and ovulatory (last wave
before ovulation) waves. Interventions on follicles at these stages to
increase Progesterone levels are considered successful [12]. It is known
that increasing Progesterone levels improve maternal acceptance and
placentation, and when this activity is established, live birth weight
increases [14]. For this purpose, the aim of the present study was to
create an accessory CL or increase the secretion volume by inducing
luteotrophic activity on the existing CL by applying hCG on different
d of the subsequent cycles of sexually stimulated and mated ewes.
It was determined that 250 IU of hCG administrated on postmating
d 5 had no effect on Progesterone levels and also did not affect
reproductive performance in goats [12]. However, there are studies
indicating that hCG administered on the 7
th
d after mating contributes
to the development of the accessory CL and increases P
4
levels [15].
In the present study, postmating hCG administration signicantly
increased P
4
levels in blood samples taken on the 22
nd
d of pregnancy.
This luteotrophic activity was thought to occur through the creation
of an accessory CL or by supporting an existing CL.
Similarly, in a study where hCG was administered on different d
after mating (d 1, 7, and 12), hCG administration on d 7 increased P
4
levels and lambing rate compared to the control group [16]. It was
thought that the success of administering hCG to the group on d 7
At the time of parturition, the placentas of singleton lambs that had been
completely expelled were weighed and compared between groups. Only
one ewe with a singleton birth demonstrated retention. According to this
comparison, the placenta weights of both groups 1 and 2 were signicantly
higher than the placenta weight of the control group (P<0.001) (FIG. 6).
Efficacy of hCG in reproductive parameters in Kangal ewes / Takci and Kivrak _____________________________________________________
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after mating was achieved by targeting the Graaan follicle of the
rst wave of follicular dynamics, as in the present study. In another
study with similar results, hCG administered in the late phase of
the cycle (d 12) after mating did not contribute to reproduction [17].
In addition to these, factors affecting live birth weight in the
prenatal stage are also important for viability and development after
birth [18, 19]. One of the factors is the level of P
4
in the material during
pregnancy, which was found to be directly proportional to birth weight
[20]. The results obtained in the present study conrm this view.
The body composition of ewes during mating and their nutritional
status during gestation also have signicant effects on live birth
weight [19]. Accordingly, the ewes were evaluated before the current
study was started and no difference was found in their condition. Any
possible difference in nutrition was eliminated by giving equal rations
to the groups. Therefore, the contribution to live birth weight and
neonatal development was entirely attributed to increased P
4
levels
and placental development during the gestation period.
P
4
level was increased with postmating hCG administration, and
live birth weight also increased in direct proportion to P
4
level.
Subsequently, the daily live weight of the lambs was monitored
during the neonatal stage. Accordingly, it was found that the daily
body weight gain of the lambs in the postmating hCG–administered
groups was signicantly higher than the control group in parallel with
the increase in live birth weight.
Although the live birth weight increased in the treatment groups,
there was no difference in the rate of dicult deliveries between
the groups. It was determined that postmating short–term P
4
administration increased P
4
levels in early pregnancy but did not
affect birth weight. This has been associated with the fact that the
increase in P
4
is not ubiquitous throughout the pregnancy but is
limited to only one period [21]. In the present study, postmating
hCG administration increased live birth weight. This was attributed
to an increase in P
4
that extended throughout the entire pregnancy.
In another study, it was determined that daily 25 mg P
4
administration
starting from the 36
th
h after mating increased the nutrients in feto–
placental uids in the later stages of pregnancy [22]. The results
obtained in the present study support this nding. The increase in live
births and placenta weight was associated with increased P
4
levels,
which improved fetal nutrition. In this respect, the results obtained
in the present study are consistent with those of a previous study
indicating that increased P
4
levels improve placentation and providing
better fetal nutrition [13]. In a previous study, it was determined that
hCG applied on post–mating d 11 and controlled intravaginal releasing
device (CIDR) protocols applied between post–mating d 7–19 increased
maternal P
4
level (in blood samples taken on d 12–17) and improved
reproductive performance in sheep [23]. In the same study, post–
mating hCG and CIDR treatments did not change the birth weights of
singletons and quadruplets but did change the birth weight of twins.
In their study, Rostami et al., found that direct supplementation of
P
4
after mating (by applying CIDR protocol) did not increase P
4
levels
on d 22 of pregnancy, whereas post–mating hCG administration did
[23]. It was believed that exogenous P
4
administration could have a
negative impact on endogenous P
4
secretion [24]. Therefore, the
authors aimed to increase endogenous Progesterone levels during
the critical phase of pregnancy.
There are also studies suggesting that postmating hCG
administration did not improve reproductive parameters [25, 26].
In the present study, postmating hCG administration increased P
4
levels and lamb numbers.
At the same time, it was determined that posmating hCG
administration reduced lamb mortality after birth until weaning [23].
The results obtained in both studies are consistent in terms of P
4
value,
but the neonatal mortality rate did not differ between the groups in
the current study.
CONCLUSION
According to the ndings of the present study, administration of
hCG after mating enhances offspring development during pregnancy
in ewes by increasing P
4
levels and placentation. Optimum eciency
can be achieved when hCG administrations are made approximately
on the fth d after mating. It was also found that postmating hCG
administration increases live birth weight and contributes to offspring
development in the neonatal stage.
ACKNOWLEDGMENT
The authors declare that no funds, grants, or other support were
received during the preparation of this manuscript.
Statement of animal rights
This study was approved by the Animal Research Ethics Committee
of Cumhuriyet University with the decision no. 361 on 11.11.2020.
Conict of interest statement
The authors have no relevant nancial or non–nancial interests
to disclose.
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