1. S162
Document heading doi: 10.1016/S1995-7645(14)60224-8
The relationship between progesterone and biochemical constituents of
amniotic fluid with placenta traits in Iranian crossbred ewes (Arkhar-
Merino伊Ghezel)
Ali Olfati1
, Gholamali Moghaddam1
, Nasroallah Moradi Kor2*
, Mitra Bakhtiari3
1
Department of Animal Science, Faculty of Agriculture, University of Tabriz, Iran
2
Department of Reproduction Physiologies, Iranian Society of Physiology and Pharmacology, Tehran, Iran
3
Department of Anatomical Sciences, Faculty of Medicine, University of Medical Sciences, Kermanshah, Iran
Asian Pac J Trop Med 2014; 7(Suppl 1): S162-S166
Asian Pacific Journal of Tropical Medicine
journal homepage:www.elsevier.com/locate/apjtm
*Corresponding author: Nasroallah Moradi Kor, Department of Reproduction
Physiology, Iranian Society of Physiology and Pharmacology, Tehran, Iran.
Tel: +98-9137684047
E-mail: Moradikor.nasroallah@yahoo.com
Foundation Project: Supported by the Department of Animal Science, Faculty of
Agriculture, University of Tabriz, Higher Education Thesis Program (Grant No. 1393/
TUAS/PH03).
1. Introduction
Since profitability in the farm animals industry is
dependent upon efficiency of production characteristics
such as growth and development after birth, the precursor
of efficiency, namely, fetal growth, which must be optimal.
There is little information available on the reproductive
characteristics of crossbred ewes particularly regarding
amniotic fluid (AF) composition. The study of biochemical
profiles both in maternal serum and AF is a useful tool
for pregnancy diagnosis and the status of growing fetus.
Blood biochemical evaluation plays an important role
in diagnosis of diseases[1]. Knowledge on biochemical
and hormonal constituents of AF can also provide useful
information about the requirements for fetus, fetal growth
and maturation. Moreover, such information may be used
as a provisional guide for formulating suitable culturing
media for in vitro cell culturing and oocyte maturation in a
particular species[2,3]. Progesterone can be used to monitor
the pregnancy status and timing of embryonic loss, as in
pregnant animals, progesterone concentrations remain
elevated throughout gestation[4]. Many of the circulatory
and transport properties of the ewe’s placenta are similar
to those of the human placenta and as such, the pregnant
sheep offers an excellent model to study the development of
AF. However, studies in sheep showed that the composition
of AF in early pregnancy (22-44 d) also changed[5]. This
change in composition may reflect changing metabolic
ARTICLE INFO ABSTRACT
Objective: To determine the values of amniotic fluid (AF) progesterone and biochemical
constituents and its associated placenta traits in Iranian crossbred ewes (Arkhar-Merino×Ghezel).
Methods: Sixty ewes (2-5 years old, weighing 40-50 kg) were treated with controlled internal
drug release induced 30 mg progesterone for 14 d and were injected with 400 IU pregnant mare
serum gonadotropin at the time of CIDR withdrawal. After the detection of estrus, ewes were
hand-mated. After expelling of each fetus accompanied by fetal membranes, 10 mL AF was taken
from fetal sac for spectrophotometer methods (glucose, urea, creatinine, total protein, cholesterol,
triglycerides, calcium and phosphorus) and radioimmunoassay (progesterone) analysis.
Results: Results indicated that there were highly positive correlations between placental
efficiency and cotyledon density (r=0.764, P<0.01), and negative correlation between placental
weight (PW) with the total volume amniotic fluid (TVAF) (r=-0.872, P<0.01). A positive relationship
was calculated between TVAF with total protein and creatinine (r=0.418, P<0.01 and r=0.639,
P<0.05, respectively). However, the correlation between the glucose and PW, cotyledon length and
calcium were significantly positive (r=0.704 and r=0.712; P<0.01, respectively). The findings of this
study demonstrated that there were no relationships between progesterone concentrations and
placental traits (P>0.01), except for PW (r=0.665).
Conclusions: In conclusion, the significant correlation between the AF biochemical and
progesterone with placental traits for the above-mentioned metabolites suggests that metabolic
changes in AF levels will reflect the condition in the AF.
Contents lists available at ScienceDirect
Article history:
Received 27 May 2014
Received in revised form 28 Jun 2014
Accepted 15 Jul 2014
Available online 20 Aug 2014
Keywords:
Biochemical
Crossbred ewes
Amniotic fluid
Placenta traits
Progesterone

2. Ali Olfati et al./Asian Pac J Trop Med 2014; 7(Suppl 1): S162-S166
S163
and transport activities as well as alteration in the relative
contribution of the fetal and placental tissues to the
amniotic and allantoic compartments. AF is important
for physiologic exchanges between fetal and maternal
tissues, so it is necessary for the efficient handling of fetal
waste products and preventing mechanical shock to the
developing fetus during entire gestation[6]. The allantoic
sac is considered traditionally and mainly as a reservoir for
fetal wastes, however, recent investigations with pigs have
shown that allantoic sac played an important role in the
accumulation of nutrients and metabolism of some factors
like uteroferrin and iron, suggesting a hitherto unrecognized
function of the allantoic sac in fetal nutrition[7]. In contrast,
AF provides a unique aqueous environment in which the
fetus develops symmetrically[8]. When it is swallowed,
amniotic fluid is a significant source of nutrients for the
fetus[9]. Survival of a newborn is affected especially by
sufficiency of the placenta[10]. A big focus has been on the
relationship between weight of placenta and birth weight
of newborn[11,12]. Before focusing on possible effects of
metabolic changes on follicle and oocyte quality, it is
necessary to determine physiological concentrations of the
most common metabolites in AF and to investigate to what
extent the AF levels and placental traits are correlated. There
is no study on placental traits in Iranian crossbred ewes.
Therefore, the main aims of this study were to determine (1)
the progesterone and biochemical constituents of AF at the
time of parturition and (2) relationships between progesterone
and biochemical composition of AF with placental traits in
Iranian crossbred ewes.
2. Materials and methods
2.1. Hormonal drugs
Controlled internal drug release (CIDR) with 30 mg of
progesterone, a progestagen analogue (InterAg, Hamilton,
New-Zealand), pregnant mare serum gonadotrophin
(Folligon; Intervet International B.V., Boxmeer, the
Netherlands) and commercially available kits (Pars Azmon,
Karaj, Iran) were purchased from Intervet Drug Industry
(Tehran, Iran).
2.2. Location and animals
This study was performed at Animal Reproduction
Laboratory of Tabriz University, Tabriz Province, Iran
(38°07’ N and 46°29’ E) from June to December 2013. Ambient
temperature during the experiment ranged from 20 °C to 24 °C
with annual rainfall in this region ranges from 226 mm to 250
mm. Sixty Iranian crossbred ewes (Arkhar-Merino×Ghezel,
2-5 years old, weighing 40-50 kg) were treated with CIDR
for 14 d and were injected with 400 IU pregnant mare serum
gonadotrophin at the time of CIDR withdrawal. After the
detection of estrus, ewes were hand-mated.
2.3. Data collection
Pregnant ewes were placed in an individual birth box
around their estimated parturition date. Placenta were
collected immediately after delivery and weighed fresh
on digital scales and the placental weight (PW) and
cotyledon number (CN) were measured and recorded.
Placental efficiency (PE) was defined as the ratio of total
birth weight (g) to placental weight (g). Cotyledon length
(CL), cotyledon depth (CD) and cotyledon width (CW) were
measured with an electronic digital caliper by randomly
selecting ten cotyledons from each placenta. Total volume
of amniotic fluid (TVAF) was measured using a graduated
cylinder. The AF were collected by disposable syringes
(10 mL) and stored in labeled plastic tubes at -20 °C until
biochemical and progesterone analysis. In the laboratory,
these samples were centrifuged at 4 000 r/min for 10 min at
approximately 22 °C to remove cellular debris, and stored
at -20 °C for later analyses. The AF samples were analyzed
for various metabolites (glucose, urea, creatinine, total
protein, cholesterol, and triglycerides) and ions (calcium,
phosphorus) by using commercially available kits by
spectrophotometric method on an auto analyzer (RA-
1000, Technicon) and radioimmunoassay (progesterone)
analysis. Standard commercial kits were used for analysis
and the procedures were adopted as recommended by the
manufacturer of these kits.
2.4. Statistical analysis
Statistical analyses of the data were done with SAS
software[13]. The mean依SE for progesterone concentrations
and various biochemical constituents of AF were
calculated. To see the magnitude of gestation age variation
in progesterone concentrations and various biochemical
constituents of AF, the data were subjected to One-
way analysis of variance (ANOVA). Significance between
means was tested using Duncan’s multiple range tests.
To determine the relationship between progesterone and
various biochemical constituents and placental traits
Pearson correlation was used for continuous data.
3. Results
The mean, standard error of mean, and range of the
progesterone and various biochemical constituents and
placental traits in the AF, are shown in Tables 1 and
2. Correlations between the concentrations of various
biochemical and placental traits are presented in Table 3.
The results of this study indicated that there were highly
positive correlations between PE and CD (r=0.764, P<0.01,
Table 3). A significantly negative correlation was calculated
for the PW and the TVAF (r=-0.872, P<0.01, Table 3). The
correlations between various biochemicals and placental
traits are presented in Table 4. A positive relationship was
calculated between TVAF with total protein and creatinine
(r=0.418, P<0.01 and r=0.639, P<0.05, respectively, Table
4). However, the correlation between the glucose and PW,
CL and calcium were significantly positive (r=0.704 and
r=0.712, P<0.01, respectively, Table 4). Other biochemical
(urea, cholesterol, triglycerides and phosphorus) studied

3. Ali Olfati et al./Asian Pac J Trop Med 2014; 7(Suppl 1): S162-S166S164
were not significantly correlated with placental traits sheep
(Table 4).
Table 1
Descriptive statistics of placental traits in Iranian crossbred ewes.
Placental trait Mean依SD Minimum Maximum
Placental weight (g) 439.3依241.7 107.00 1 132.00
Cotyledon number 72.80依19.62 23.00 141.00
Placental efficiency 10.60依3.06 4.90 29.60
Cotyledon length (mm) 23.41依2.03 18.69 31.03
Cotyledon depth (mm) 7.85依0.61 5.47 11.20
Cotyledon width (mm) 16.36依1.05 12.23 21.07
Total volume of amniotic fluid (mL) 857.00依98.23 722.00 1 028.00
Table 2
Descriptive statistics of progesterone and biochemical constituents in AF in
Iranian crossbred ewes.
Biochemical constituent Mean依SD Minimum Maximum
Glucose (mg/dL) 2.62依0.19 0.23 4.41
Urea (mg/dL) 78.1依17.44 62.36 88.10
Creatinine (mg/dL) 11.69依3.23 9.67 16.77
Total protein (gr/dL) 1.01依0.11 0.84 1.49
Vholesterol (mg/dL) 2.95依0.87 2.15 4.35
Triglycerides (mg/dL) 0.79依0.07 0.45 1.12
Calcium (mg/dL) 3.34依1.08 2.12 5.17
Phosphorus (mg/dL) 3.98依1.12 3.07 4.78
Progesterone (ng/mL) 1.19依0.48 0.72 1.33
Correlations between the progesterone concentrations
and placental traits are presented in Table 5. Generally,
low levels of progesterone were detected in AF of Iranian
crossbred ewes. The findings of this study demonstrated
that there were no relationships between progesterone
concentrations and placental traits (P>0.01), except for PW
(r=0.665, Table 5).
Table 3
Correlation coefficients of placental traits in Iranian crossbred ewes.
Placental trait PW (g) CN PE CL (mm) CD (mm) CW (mm) TVAF (mL)
PW 0.232 0.125 -0.158 0.089 0.170 -0.872
*
CN 0.015 0.315 0.114 0.078 -0.258
PE 0.099 0.764
**
0.212 0.025
CL 0.145 -0.231 0.156
CD 0.346 0.256
CW -0.214
PW: Placental weight; CN: Cotyledon number; PE: Placental efficiency; CL:
Cotyledon length; CD: Cotyledon depth; CW: Cotyledon width; TVAF: Total
volume of amniotic fluid. *
: P<0.05, **
: P<0.01.
Table 4
Correlation coefficients between various biochemical’s and placental traits in
Iranian crossbred ewes.
Biochemicals PW CN PE CL CD CW TVAF
Glucose 0.704
**
0.061 -0.150 0.006 0.255 0.055 0.310
Urea -0.071 0.265 0.143 0.153 0.105 0.083 -0.211
Creatinine 0.213 -0.159 0.032 0.058 0.277 -0.140 0.639
*
Total protein 0.315 -0.221 0.425 0.035 -0.378 0.112 0.418
**
Cholesterol 0.314 0.012 3 0.104 -0.255 0.301 0.221 0.157
Triglycerides 0.209 0.109 0.088 -0.273 0.351 0.120 0.346
Calcium 0.104 0.251 -0.028 0.712
**
0.055 -0.310 0.312
Phosphorus 0.123 -0.258 0.036 0.089 0.201 0.307 0.002
PW: Placental weight; CN: Cotyledon number; PE: Placental efficiency; CL:
Cotyledon length; CD: Cotyledon depth; CW: Cotyledon width; TVAF: Total
volume of amniotic fluid. *
: P<0.05, **
: P<0.01.
Table 5
Correlation coefficients of between progesterone concentration in AF and
placental traits in Iranian crossbred ewes.
PW CN PE CL CD CW TVAF
Progesterone conc. 0.665
**
0.305 -0.154 0.223 0.012 0.401 0.109
PW: Placental weight; CN: Cotyledon number; PE: Placental efficiency; CL:
Cotyledon length; CD: Cotyledon depth; CW: Cotyledon width; TVAF: Total
volume of amniotic fluid. **
: P<0.01.
4. Discussion
Parturition is the physiological process by which the
pregnant uterus delivers the fetus/fetuses and placenta from
the mother. In mammalians, the foetus is surrounded by
amnion and allantois which establish a perfect water and
biochemical balance. This study for the first time describes
the relationship between progesterone and biochemical
constituents of AF with placental traits in Iranian crossbred
ewes (Arkhar-Merino×Ghezel) in northwest of Iran.
Since the placenta is known to produce progesterone,
it is pertinent to examine the role of these hormones in
AF. Progesterone is a hormone which regulates various
reproductive functions. Progesterone plays a key role in
regulating the length of estrous cycle and implantation
of blastocysts[14]. The findings of this study demonstrated
that there were no relationships between progesterone
concentrations and placental traits (P>0.01), except for
PW (r=-0.665). Strong relations between progesterone
concentration and PW was observed. It seems that increase in
PW led to prolonged duration of secretion progesterone from
AF. Our data demonstrated for the first time that progesterone
concentrations were correlated with PW. In addition,
since abnormal corpora lutea is associated with either low
progesterone concentrations, or normal values for a shortened
period, AF progesterone concentrations may also be used to
examine luteal function in livestock. Bazer et al. indicate
that the placenta ovine is contributing significantly to the
concentrations of the sex steroids in AF and in plasma from
the ovarian and uterine veins, and general circulation[15].
Therefore, it is important to understand the progesterone
interaction that happens in the AF of the ewe during oestrus
cycle, pregnancy, parturition and postpartum in breeding and
non-breeding seasons.
The results of this study demonstrated that PE also
correlated positively with CD (r=0.764, P<0.01), which is
similar to the observations by other investigators[16,17].
Uterine capacity is described by the total placental mass
which a female can carry to term[18]. PE was developed as an
indicator of uterine capacity[19]. PE has been used commonly
for livestock species, which produce larger birth type, such
as pig and sheep[20,21]. Osgerby et al. stated that nutrient
deprivation during the pregnancy led to a decrease in fetal
and PW but an increase in PE[22]. Konyali et al. suggested
that small placentas are more efficient than large placenta
in Turkish Saanen goats[23], and probably large placenta
require more nutrients[20,21]. Konyali et al. also suggested that
placental traits were affected by the birth type rather than
the sex of the kids[23]. Nowak et al. suggested the existence
of paternal genetic affected placental traits in domestic

4. Ali Olfati et al./Asian Pac J Trop Med 2014; 7(Suppl 1): S162-S166
S165
animals[24].
The placenta is a multifaceted organ that plays critical
roles in maintaining and protecting the developing fetus[25].
Interestingly, PW had a highly significant negative correlation
with TVAF (r=-0.872, P<0.01). Thus, placental growth
precedes fetal growth because the fetus requires a functional
placenta for obtaining nutrients and gases for its growth and
development. However, the majority of placental growth, at
least in terms of PW, occurs during the first two-thirds of
pregnancy, and the placenta achieves its maximum weight
by day 90 in sheep[17]. Thus, the fetus has obtained only 10%
of its eventual birth weight by the time when the placenta
has reached its maximum size. The size and nutrient transfer
capacity of the placenta play a central role in determining
the prenatal growth trajectory of the fetus and hence directly
influences birth weight[26].
A broad knowledge of concentration of constituents in AF is
of the utmost importance in understanding fetal metabolism
and identifying pathological conditions during pregnancy[27].
The concentration of constituents in allantoic compartments is
influenced by the exchange through the placenta, metabolic
products of the fetus, fetal urine formation and fluid flow
through the urachus or urethra and fetal secretions from lung
and salivary glands[28].
Because there is little information on correlation coefficients
between various electrolytes and placental traits, one can
only speculate on the significance of these electrolytes on
growth and viability of ewe’s fetus. However, the correlation
between the glucose and PW was significantly positive
(r=0.704, P<0.01). Glucose plays an important role in fetal
metabolism because it is one the major energy source for the
embryo, maybe metabolized by the AF through the anaerobic
pathways, leading to lactate formation. Albuquerque et
al. showed that, as for AF (human and ovine), changes in
volume and content of glucose in AF were associated with
changes in electrolytes and their ratios[29]. Reddy et al.
performed biochemical studies in ewe AF at different stages of
pregnancy, obtaining significant differences in mean levels of
glucose[30]. They concluded that decreased glucose levels at
the end of pregnancy might have been caused by fetal intake
of glucose due to the development of the fetal swallowing
reflex. Serum biochemical parameters varies widely and
preferably glucose and urea individually or in combination
are the useful parameters in diagnosis of physiological and
pathological condition in ewes[31].
Despite intensive studies on facilitative protein transporters,
little is known about functional protein in AF livestock. The
results of this paper have demonstrated repeatedly that a
positive relationship was calculated between TVAF with total
protein and creatinine (r=0.418, P<0.01). Protein is due to
the important role of proteins in regulation of growth and
differentiation[31]. However, the AF proteins are regarded as
nutritional status indicators of normal fetal growth[32]. In a
recent study, Florida native ewes were investigated and it
was found that placental cotyledons, formed placentomes
critical for the exchange of micronutrients (e.g., amino
acids, glucose), as well as gases between the conceptus and
maternal system[15]. AF proteins were apparently derived
from both maternal and foetal sources. The maternal
contribution was principally the globulin fraction, while the
fetus contributed prealbumin, albumin, fetoprotein and sex
hormone binding globulin[33]. According to Reddy et al., the
lower concentration of AF total protein could be attributed
to the absence of the fibrinogen and other proteins due to
foetal immunity[30]. The foetus synthesized all its proteins
from the amino acids derived from the mother, proteins
were used mainly for synthesis rather than oxidation or
gluconeogenesis[34]. Therefore, understanding the normal
values of various biochemicals could be the useful indicator
in determination of the physiological aspects in nonpregnant
or pregnant ewes. Ocak et al. reported that AF composition
in mammals is influenced by the excretion of fetal urine and
that changes in the concentration of many components during
late pregnancy may reflect fetal metabolic activity[17].
A highly positive correlation was showed between TVAF
and creatinine (r=0.639, P<0.05). Creatinine is an indicator
of muscle mass as well as renal function[35]. And also
glomerular filtration in the fetal kidney can be assessed by
the concentrations of creatinine and urea in AF[36]. Anitha
and Thangavel reported that in Madras Red breed of ewes, as
gestation advanced, the level of creatinine AF raised, which
might indicate increased protein metabolism in the fetus[33].
Also a highly positive correlation was observed between CL
and calcium (r=0.712, P<0.01). Calcium plays an important
role in gonadotrophin regulation of ovarian steroidogenesis
and ovulation. Also calcium and phosphorus are important in
the development of the fetal skeleton. Tabatabaei and Mamoei
have demonstrated that it would be expected that the fetus,
in conserving them (Ca2+
and P
+
), would excrete very little into
the AF[8]. The various ions could help the mitosis of the fetal
cells through the formation of thrombin, a potent mitogen.
In conclusion, understanding relationship between
progesterone and biochemical constituents of AF with
placenta traits during parturition is an important determinant
of pregnancy outcome, and ultimately, life-long health and
productivity of an individual. In conclusion, the significant
correlation between the AF biochemical and progesterone
with placental traits for the above-mentioned metabolites
suggests that metabolic changes in AF levels will reflect the
condition in AF. The authors of this paper suggested that
further study on the correlation among AF, placental traits
and postnatal behavior in farm animals industry is required
not just on the ewes but also on their lambs. This could have
a significant effect on how producers manage and maximize
lamb survivability and profitability. Also, further research
should focus on the collection of AF by the laparoscopic
technique from live ewes for the composition of the AF,
especially the multifarious enzyme concentrations.
Conflict of interest statement
We declare that we have no conflict of interest.
Acknowledgements
The authors would like to acknowledge Dr. N. Pirany and

5. Ali Olfati et al./Asian Pac J Trop Med 2014; 7(Suppl 1): S162-S166S166
Dr. S.A. Rafat, Dr. M.M. Moeini and F. Hozhabri for their
help and collaboration in this work. This work is supported
by the Department of Animal Science, Faculty of Agriculture,
University of Tabriz, with the grant No. 1393/TUAS/PH03 of
Higher Education Thesis Program.
References
[1] Moghaddam GH, Olfati A. Metabolic profiles in crossbreed ewes
in late pregnancy. In: Koonawootrittriron S, Suwanasopee T,
Jattawa D, Boonyanuwat K, Skunmun P, editors. Proceedings
of the 15th AAAP Animal Science Congress; 2012 Nov 26-30;
Thailand: Thammasat University, Rangsit Campus; 2012, p. 2207-
2210.
[2] Gérard N, Loiseau S, Duchamp G, Seguin F. Analysis of the
variations of follicular fluid composition during follicular growth
and maturation in the mare using proton nuclear magnetic
resonance (
1
H NMR). Reproduction 2002; 124: 241-248.
[3] Duarte AB, Araújo VR, Chaves RN, Silva GM, Magalhães-Padilha
DM, Satrapa RA, et al. Bovine dominant follicular fluid promotes
the in vitro development of goat preantral follicles. Reprod Fertil
Dev 2012; 24: 490-500.
[4] Boscos CM, Samartzi FC, Lymberopoulos AG, Stefanakis A,
Belibasaki S. Assessment of progesterone concentration using
enzymeimmunoassay, for early pregnancy diagnosis in sheep and
goats. Reprod Domest Anim 2003; 38: 170-174.
[5] Li N, Wells DN, Peterson AJ, Lee RS. Perturbations in the
biochemical composition of fetal fluids are apparent in surviving
bovine somatic cell nuclear transfer pregnancies in the first half
of gestation. Biol Reprod 2005; 73: 139-148.
[6] Khadjeh GH, Ranjbar R, Salehi M, Banankhojasteh SM.
Biochemical evaluation of amniotic fluid during different stages
of gestation in the goat. Iran J Vet Res 2007; 8: 266-269.
[7] Kwon HJ. Amino acids, polyamines and nitric oxide synthesis in
the ovine conceptus [dissertation]. Texas: Texas University; 2003.
[8] Tabatabaei S, Mamoei M. Changes in the biochemical composition
of fetal fluids and maternal blood serum during different days of
gestation in cattle. Comp Clin Pathol 2012; 21: 1005-1012.
[9] Schmidt W. The amniotic fluid compartment: the fetal habitat.
Adv Anat Embryol Cell Biol 1992; 127: 1-100.
[10] Mellor DJ, Stafford KJ. Animal welfare implications of neonatal
mortality and morbidity in farm animals. Vet J 2004; 168: 118-133.
[11] Osgerby JC, Gadd TS, Wathes DC. The effects of maternal nutrition
and body condition on placental and foetal growth in the ewe.
Placenta 2003; 24: 236-247.
[12] Madibela OR. Placental mass of grazing Tswana goats kidding
at two different periods during the dry season. J Biol Sci 2004; 4:
740-743.
[13] SAS Institute Inc. SAS user’s guide. Cary, NC: SAS Institute Inc.;
2003.
[14] Tomac J, Cekinovi D, Arapovic J. Biology of the corpus luteum.
Periodicum Biologorum 2011; 113(1): 43-49.
[15] Bazer FW, Spencer TE, Thatcher WW. Growth and development of
the ovine conceptus. J Anim Sci 2012; 90: 159-170.
[16] Ocak S, Onder H. Placental traits and maternal intrinsic factors
affected by parity and breed in goats. Anim Reprod Sci 2011; 128:
45-51.
[17] Ocak S, Ogun S, Gunduz Z, Önder H. Relationship between
placental traits and birth related factors in Damascus goats. Livest
Sci 2014; 161: 218-223.
[18] Wilson ME, Biensen NJ, Ford SP. Novel insight into the control of
litter size in pigs, using placental efficiency as a selection tool. J
Anim Sci 1999; 77: 1654-1658.
[19] Wilson ME, Ford SP. Comparative aspects of placental efficiency.
Reprod Suppl 2001; 58: 223-232.
[20] Mesa H, Safranski TJ, Johnson RK, Lamberson WR. Correlated
response in placental efficiency in swine selected for an index of
components of litter size. J Anim Sci 2003; 81: 74-79.
[21] Dwyer CM, Calvert SK, Farish M, Donbavand J, Pickup HE. Breed,
litter and parity effects on placental weight and placentome
number, and consequences for the neonatal behaviour of the
lamb. Theriogenology 2005; 63: 1092-1110.
[22] Osgerby JC, Wathes DC, Howard D, Gadd TS. The effect of
maternal undernutrition on ovine fetal growth. J Endocrinol 2002;
173: 131-141.
[23] Konyali A, Tölü C, Das G, Savas T. Factors affecting placental
traits and relationships of placental traits with neonatal behaviour
in goat. Anim Reprod Sci 2007; 97: 394-401.
[24] Nowak R, Porter RH, Lévy F, Orgeur P, Schaal B. Role of mother-
young interactions in the survival of offspring in domestic
mammals. Rev Reprod 2000; 5: 153-163.
[25] Wilson ME. Role of placental function in mediating conceptus
growth and survival. J Anim Sci 2002; 80 (E. Suppl 2): E195-E201.
[26] Wallace JM, Bourke DA, Aitken RP. Nutrition and fetal growth:
paradoxical effects in the overnourished adolescent sheep. J
Reprod Fertil Suppl 1999; 54: 385-399.
[27] Prestes NC, Chalhoub MC, Lopes MD, Takahira RK. Amniocentesis
and biochemical evaluation of amniotic fluid in ewes at 70, 100
and 145 days of pregnancy. Small Rumin Res 2001; 39(3): 277-281.
[28] Banan Khojasteh SM, Khadjeh GH, Ranjbar R, Salehi M. Studies
on biochemical constituents of goat allantoic fluid during different
stages of gestation. Egypt J Sheep Goat Sci 2011; 6(1): 1-5.
[29] Albuquerque CA, Nijland MJ, Ross MG. Human and ovine
amniotic fluid composition differences: Implications for fluid
dynamics. J Matern Fetal Med 1999; 8: 123-129.
[30] Reddy AP, Reddy VSC, Rao AS, Sharma GP, Reddy GUN, Reddy
TJ, et al. Biochemical studies in the ewe (Ovis aries) amniotic fluid
during different phases of gestation. Indian J Anim Sci 1995; 10:
321-323.
[31] Khatun A, Wani GM, Bhat JIA, Choudhury AR, Khan MZ.
Biochemical indices in sheep during different stages of
pregnancy. Asian J Anim Vet Adv 2011; 6: 175-181.
[32] Tisi DK, Emard JJ, Koski KG. Total protein concentration in
human amniotic fluid is negatively associated with infant birth
weight. J Nutr 2004; 134: 1754-1758.
[33] Anitha A, Thangavel A. Biochemical profile of ovine amniotic and
allantoic fluids. Tamilnadu J Vet Anim Sci 2011; 7(6): 262-267.
[34] Jainudeen MR, Hafez ESE. Gestation, prenatal physiology, and
parturition. In: Hafez SES, Hafez B, editors. Reproduction in farm
animals. 7th ed. Hoboken: Wiley, John & Sons, Incorporated; 2000,
p. 140-156.
[35] Ozegbe PC. Comparative biochemical assessment of the amniotic
fluid and maternal plasma of pregnant rabbits. Vet Arh 2005; 75(5):
431-437.
[36] Ring E, Hofmann H, Erwa W, Riccabona M, Zobel G, Häusler M.
Amniotic fluid N-acetyl-beta-D-glucosaminidase activity and
renal abnormalities. Arch Dis Child 1991; 66: 1147-1149.