https://doi.org/10.52973/rcfcv-e34480
Received: 04/07/2024 Accepted: 19/08/2024 Published: 30/09/2024
1 of 7
Revista Científica, FCV-LUZ / Vol. XXXIV, rcfcv-e34480
ABSTRACT
This study investigated the frequency, risk factors, and metabolic
indicators for detecting subclinical ketosis (SCK) in Ouled Djellal
ewes. Out of 54 enrolled ewes, those with BHB ≥ 0.86 mmol·L
-1
without clinical signs formed the SCK group, while ewes with BHB
< 0.86 mmol·L
-1
were healthy controls, either in late pregnancy or
early lactation. The SCK frequency was higher in early lactation
(37%). Increased risk was associated with twin–bearing (OR=4.96,
95%CI=1.967–12.503, P=0.001) and thin ewes with BCS < 2.5 (OR=2.74,
95%CI=0.71–10.73, P=0.003). SCK ewes had signicantly lower glucose,
triglycerides, cholesterol, Ca, Mg, Na, and K levels, but higher AST,
ALT, GGT, ALP, LDH, and CK levels. The best diagnostic indicators
were Ca (AUC 94.4%, cut–off < 81 g·L
-1
, SE 77.46%, SP 100%), AST
(AUC 84.4%, cut–off > 94.19 U·L
-1
, SE 74.65%, SP 83.78%), and K (AUC
79.3%, cut–off 4.1 mmol·L
-1
, SE 71.83%, SP 75.68%). Monitoring BHB
and BCS, especially in twin–bearing ewes during the transition period,
is recommended for ketosis prevention. Further large–scale validation
of these metabolic indicators as SCK predictors in Ouled Djellal ewes
is warranted.
Key words: Metabolic indicators; Ouled Djellal ewes; prevalence;
risk factors; subclinical ketosis
RESUMEN
Este estudio investigó la frecuencia, los factores de riesgo y los
indicadores metabólicos para detectar cetosis subclínica (SCK) en
ovejas Ouled Djellal. De 54 ovejas seleccionadas, aquellas con BHB
≥ 0,8 mmol·L
-1
sin signos clínicos formaron el grupo SCK, mientras
que, las ovejas con BHB < 0,8 mmol·L
-1
fueron controles sanos, ya sea
al nal de la gestación o al principio de la lactancia. La frecuencia
de SCK fue mayor al inicio de la lactancia (37 %). El mayor riesgo se
asoció con la gestación gemelar (OR=4,96, IC del 95 %=1,967–12,503,
P=0,001) y ovejas delgadas con BCS < 2,5 (OR=2,74, IC del 95 %=0,71–
10,73, P=0,003). Las ovejas SCK tenían niveles signicativamente
más bajos de glucosa, triglicéridos, colesterol, Ca, Mg, Na y K, pero
niveles más altos de AST, ALT, GGT, ALP, LDH y CK. Los mejores
indicadores diagnósticos fueron Ca (AUC 94,4 %, punto de corte
< 81 g·L
-1
, SE 77,46 %, SP 100 %), AST (AUC 84,4 %, punto de corte >
94,19 U·L
-1
, SE 74,65 %, SP 83,78 %) y K (AUC 79,3 %, punto de corte
4,1 mmol·L
-1
, SE 71,83 %, SP 75,68 %). Se recomienda monitorear
BHB y BCS, especialmente en ovejas con gestación gemelar durante
el período de transición, para prevenir la cetosis. Se justica una
validación adicional a gran escala de estos indicadores metabólicos
como predictores de SCK en ovejas Ouled Djellal.
Palabras clave: Indicadores metabólicos; ovejas Ouled Djellal;
prevalencia; factores de riesgo; cetosis subclínica
Risk factors and metabolic indicators associated with the percentage frequency
of subclinical ketosis on Ouled Djellal ewes in eastern highlands of Algeria
Factores de riesgo e indicadores metabólicos asociados con la frecuencia de cetosis
subclínica en ovejas Ouled Djellal en las tierras altas orientales de Argelia
Meriem Bouzenzana
1,2
* , Abdennour Azizi
1
, Sabah Hanachi
3,4
, Karima Benembarek
4
, Mohammed–Ezine Zebiri
5
, Nedjoua Arzour–Lakehal
6
,
Touk Meziane
1
1
Batna1 University, Institute of Veterinary Sciences and Agronomic Sciences, Department of Veterinary Sciences, Laboratory of Environment, Health
and Animal Production (ESPA). Batna, Algeria.
2
Constantine 1–Frères Mentouri University, Institute of Veterinary Sciences, Department of Animal Production. Constantine, Algeria.
3
Constantine 3 – Salah Boubnider University, Medicine Faculty, Molecular Biology and genetics Laboratory. Constantine, Algeria.
4
University Hospital Center, Biochemistry laboratory. Constantine, Algeria.
5
Veterinarian Doctor, Abassi Larbi Pilot Farm. Bordj Bou Arreridj, Algeria.
6
Constantine 1–Frères Mentouri University, Institute of Veterinary Sciences, Research laboratory PADESCA. Constantine, Algeria.
*Corresponding author: meriem.bouzenzana@univ–batna.dz
Metabolic Indicators of Subclinical Ketosis in Ouled Djellal Ewes / Bouzenzana et al. _______________________________________________
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INTRODUCTION
Ketonemia is a common metabolic disorder affecting sheep (Ovis
aries) and goats (Capra hircus), especially during late pregnancy and
early lactation [1, 2, 3, 4]. It reects disturbances in carbohydrate and
fat metabolism resulting from severe negative energy balance (NEB)
[5]. NEB promotes NEFAs (Non–esteried fatty acids) mobilization
from adipose tissue and increased hepatic ketone body production,
leading to pregnancy toxemia (PT) in late pregnancy or lactation ketosis
in early lactation, in clinical or subclinical forms [1, 4, 6]. Subclinical
ketosis (SCK) is characterized by hypoglycemia and hyperketonemia
without clinical signs and can rapidly degenerate into clinical
ketosis under unfavorable conditions [7, 8]. Among ketone bodies,
β–hydroxybutyrate acid (BHB) is a sensitive marker for detecting
maternal undernutrition and diagnosing ketosis in ewes [5, 9].
Commonly the risk of ketosis occurs most in older animals with
multiple fetuses, which increases up to third parity and exacerbates
with poor nutritional management [2, 3, 5, 10]. Other stress factors
including concurrent diseases, poor sanitation, and severe cold affect
energy balance and cause ketosis [3, 10, 11, 12].
Ketosis being the most frequent cause of deaths in pregnant
ewes and causing economic losses by reducing productivity and
infertility problems [12, 13]. It is also a risk factor for postpartum
mastitis, dystocia, and retained fetal membranes [14, 15]. Ketosis can
negatively affect lamb health, with up to 20% reduced lamb viability,
and increased morbidity due to lower birth weight and inadequate
colostrum production [12, 14, 15, 16].
Understanding the pathological changes associated with SCK is
crucial for developing effective diagnostic, timely interventions and
successful treatment [2, 17]. However, SCK is less studied in dairy
ewes [16], and no studies have been conducted in Algeria in Ouled
Djelall ewes. This study aimed to determine the prevalence of SCK and
associated risk factors in Ouled Djelall ewes during the periparturient
period, and to identify biomarkers for early SCK diagnosis.
MATERIALS AND METHODS
Animals
This study involved fty–four clinically healthy Ouled Djellal ewes (10%
of the total farm ewes), aged 3–6 years, with an average body condition
score (BCS) of 2.89 ± 0.37 and weighing 59.25 ± 4.02 kg (Maquinaria
Bar Hosteleria, MBHTMZ150, Spain) at the beginning of the research.
Study Area
The research was conducted at the Abassi Larbi pilot farm in Bordj
Bou Arreridj Province, Eastern Algeria (35°N | 4°E, altitude 1065 m),
characterized by a semi–arid climate. The 2020/2021 campaign had
below–average rainfall (277.6 mm) and an annual average temperature
of 15.9°C.
Feeding and breeding management
Estrus cycles were synchronized using the ram effect in
late September, with pregnancy confirmed by transabdominal
ultrasonography (DRAMINSKI iScan2, Poland) in 45 days later.
Ewes grazed on natural pasture daily (11:00 to 17:00) and received
wheat straw (1 kg·ewe
-1
·day
-1
) and 500 g of commercial concentrate
composed of maize, wheat bran, barley, carob, soybean, molasses,
salt, dicalcium phosphate, calcium carbonate, and CMV mineral
and vitamin supplement. The corresponding nutritional value of
the concentrate was 14.3% crude protein (DM), 3.3% crude fat (DM),
5.7% crude ber (DM), 0.2% crude ash (DM), 0.85% calcium, and
0.6% phosphorus. They were provided fresh water twice daily and
systematically vaccinated and dewormed.
Study design
Ewes were divided into two groups based on blood BHB
concentration either during late pregnancy or early lactation: healthy
(BHB < 0.86 mmol·L
-1
) and SCK (BHB > 0.86 mmol·L
-1
). All ewes had no
clinical symptoms. Before blood sampling, BCS was assessed on a
1–5 scale [19].
Sample Collection
Blood samples were collected using vacutainer heparinized tubes
from the jugular vein in the morning before feeding and centrifuged at
3000 rpm for 10 min (TDZ4–WS, Bioridge, Shanghai, China). Samples
were taken during late pregnancy (18–3 days prepartum) and early
lactation (3–18 days postpartum) and the plasma stored at -20°C
until analysis.
Biochemical Analysis
The blood BHB concentrations were measured at ewe–side with
rapid test strips using a handheld meter (FreeStyle Optium H for β–
Ketone, Abbott Diabetes Care Ltd, Witney, Oxon, UK). This handheld
meter was validated for use in sheep [20]. Whereas, plasma glucose,
triglycerides (TGs), cholesterol, aspartate aminotransferase (AST),
alanine aminotransferase (ALT), gamma–glutamyl transferase
(GGT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH),
creatine kinase (CK), calcium (Ca), phosphorus (P), magnesium (Mg),
sodium (Na), and potassium (K) were all determined by an automatic
biochemical analyzer (ADVIA® 1800 Chemistry System, Siemens
Healthcare, Germany) at the biochemistry laboratory of the university
hospital center of Constantine province.
Statistical Analysis
The data were examined utilizing the statistical program SPSS
version 23.0. The variables were reported as the mean and standard
error of the mean (SEM). A signicance level of P<0.05 was used.
Qualitative factors were categorized for logistic regression analyses.
The pregnancy number was classied into two categories: 2 (biparous)
and ≥ 3 (multiparous). The body condition score (BCS) of ewes was
classied into three categories: thin (< 2.5), medium (2.5–3.5) and
obese (> 3.5). The pregnancy size was classied into two classes:
1 (single) and 2 (twin). The period and sampling into late pregnancy
and early lactation.
A chi–square test was used to assess potential risk factors linked
with SCK outcomes for categorical variables. Variables having a
signicance level of P<0.05 were further analyzed using binary logistic
regression. The SCK disease, represented as a binary variable, was
treated as the dependent variable, while the other factors were
treated as independent variables. The Hosmer and Lemeshow
goodness of t test was used to validate the nal model.
An ANOVA two–factor test was used to assess the variability of
metabolic blood parameters in sheep with and without SCK during late
pregnancy and early lactation. Ultimately, the cut–off points or critical
TABLE I
Percentage frequency and risk factors associated with SCK in Ouled Djella ewes
Risk factors
Categorized
variables
Healthy ewes SCK ewes
Ch–square df P value
N
percentage
frequency
N
percentage
frequency
Physiological
state
LP 23 21.3% 31 28.7%
3.33 1 0.068
EL 14 13.0% 40 37.0%
Parity
Biparous 10 9.3% 13 12.0%
1.103 1 0.294
Multiparous 27 25.0% 58 53.7%
Litter size
Single 25 23.1% 19 17.6%
16.77 1 0.000*
Twins 12 11.1% 52 48.1%
BCS
Thin 7 6.5% 40 37.0%
16.703 2 0.000*
Medium 24 22.2% 19 17.6%
Obese 6 5.6% 12 11.1%
The Chi–square statistic is signicant at the 0.05 level. LP : late pregnancy; EL: early lactation
TABLE II
Association between litter size and BCS with the risk of SCK occurrence
Risk factors
Categorized
variables
B S.E Wald df P value OR
95%C.I for OD
Lower Upper
Litter size Twins 1.601 0.472 11.522 1 0.001 4.960 1.967 12.503
BCS
Obese 11.406 2 0.003
Thin 1.008 0.687 2.156 1 0.142 2.741 0.713 10.533
Medium -0.818 0.631 1.681 1 0.195 0.441 0.128 1.520
Constant -0.194 0.586 0.109 1 0.741 0.824
_____________________________________________________________________________Revista Cientifica, FCV-LUZ / Vol. XXXIV, rcfcv-e34480
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thresholds of metabolic predictors for SCK diagnosis (dependent
binary variable) were established by receiver operating characteristic
(ROC) analysis. The diagnostic precision of the selected parameters
was evaluated using the area under the curve (AUC). Only signicant
variables were chosen for prediction based on the hypothesis that
the AUC is not equal to 0.5 (H
o
: AUC = 0.5 vs H
o
: AUC ≠ 0.5; P<0.05).
The ideal thresholds of the signicant parameters were determined
by calculating Youden’s index.
RESULTS AND DISCUSSION
Percentage frequency and risk factors associated with SCK in
Ouled Djellal ewes
The percentage frequency of SCK was higher during early lactation
(37%) than in late pregnancy (28.7%) and augmented with the
increase in parity number, with the maximum cases was occurred
in multiparous ewes (53.7%). Only the litter size and the BCS were
signicantly (P<0.001) associated with SCK. While the chi–square
test did not detect any signicant differences related to physiological
state and parity on the occurrence of SCK (TABLE I).
Likewise, these ndings also indicated that ewes bearing twins and
under–conditioned ewes had a higher risk for developing SCK. The
risk of SCK increases approximately 5 times in ewes bearing twins
compared to ewes with simple litter size (OR=4.96, 95% CI=1.967–12.503,
P=0.001), and approximately 3 times in thin ewes compared to over–
conditionned ewes (OR=2.74, 95% CI=0.71–10.73, P=0.003) (TABLE II).
During the early lactation, Ouled Djellal ewes were also prone to
ketosis, related to the deciency of energy in ewes during this period.
Similar rates have been reported in dairy ewes (Lacaune breed), with
a higher percentage frequency during early lactation (33%) compared
to late pregnancy (18%) [1]. However, ewes are more susceptible to
ketosis in the last few weeks of pregnancy due to increased fetal
energy demands and often inadequate nutrition [11, 21].
Several factors contribute to the development of SCK in ewes.
This study identied litter size, and a BCS as signicant risk factors
in Ouled Djellal ewes. Under–conditioned ewes (BCS < 2.5), and those
carrying multiple fetuses were at higher risk of SCK due to NEB and
impaired gluconeogenesis [2, 8, 11, 15]. Higher blood BHB levels
correlated with lower BCS, suppressed appetite, reduced ruminal
motility, and further deterioration of body condition [1]. Microcytic
hypochromic anemia, associated with SCK and low BCS, indicated
insucient feed intake in affected ewes [8]. BCS loss in postpartum
increases the risk of ketosis, reduces milk yield and reproduction
performance, and causes early embryonic death [1]. Hence, BCS is
essential for managing feeding programs and detecting NEB and
metabolic diseases in sheep herds.
TABLE III
Blood metabolic parameters comparison between ewes with and without SCK
Metabolic Indicators Period
Group P
CON SCK Group Period
Group ×
Period
Energetic
Indictors
BHB
(mmol·L
-1
)
LP 0.7±0
a
1.5 ± 0.1
b
EL 0.7±0
a
1.5 ± 0.1
b
Glucose
(mmol·L
-1
)
LP 2.77 ± 0.11
a
2.33 ± 0.05
b
0.0001 0.721 0.059
EL 2.66 ± 0.05 2.49 ± 0.05
TGs
(g·L
-1
)
LP 0.32 ± 0.02
aA
0.23 ± 0.01
b
0.001 0.002 0.088
EL 0.23 ± 0.01
B
0.21 ± 0.01
Cholesterol
(g·L
-1
)
LP 1.63 ± 0.05
a
1.42 ± 0.05
bA
0.0001 0.387 0.08
EL 1.68 ± 0.07
a
1.26 ± 0.02
bB
Enzymatic
indicators
AST
(U·L
-1
)
LP 82.04 ± 1.75
aA
101,91 ± 3.47
bA
0.0001 0.001 0.729
EL 94.67 ± 2.99
Ab
117.25 ± 3.78
bB
ALT
(U·L
-1
)
LP 12.77 ± 0.34
aA
14.17 ± 0.38
bA
0.003 0.005 0.91
EL 14.1 ± 0.57
B
15.61 ± 0.45
B
GGT
(U·L
-1
)
LP 41.75 ± 0.73
aA
44.53 ± 0.89
bA
0.013 0.0001 0.574
EL 53.34 ± 1.48
B
57.71 ± 1.48
B
ALP
(U·L
-1
)
LP 102.18 ± 7.93
a
151.68 ± 10.47
bA
0.0001 0.225 0.061
EL 93.17 ± 7.77
a
193.27 ± 13.53
bB
CK
(U·L
-1
)
LP 86.6 ± 1.84
a
108.58 ± 6.87
bA
0.001 0.074 0.079
EL 87.05 ± 3.8
a
159.39 ± 16.75
bB
LDH
(U·L
-1
)
LP 260.09 ± 5.73
aA
291.38 ± 8.14
bA
0.005 0.002 0.885
EL 296.16 ± 10.37
B
330.83 ± 12.07
B
Mineral
indicators
Ca
( mmol·L
-1
)
LP 2.17 ± 0.02
a
1.83 ± 0.04
b
0.0001 0.463 0.648
EL 2.22 ± 0.02
a
1.84 ± 0.04
b
P
( mmol·L
-1
)
LP 1.29 ± 0.04
aA
1.59 ± 0.04
bA
0.873 0.077 0.0001
EL 1.67 ± 0.06
aB
1.4 ± 0.04
bB
Mg
(mmol·L
-1
)
LP 0.75 ± 0.008
a
0.69 ± 0.01
b
0.0001 0.816 0.055
EL 0.78 ± 0.01
a
0.66 ± 0.01
b
Na
(mmol·L
-1
)
LP 144.6 ± 0.4
a
141.00 ± 0.8
b
0.0001 0.005 0.238
EL 147,5 ± 0,5
a
142,2 ± 0,6
b
K
(mmol·L
-1
)
LP 4.37 ± 0.09
a
3.98 ± 0.05
b
0.0001 0.423 0.429
EL 4.48 ± 0.11
a
3.98 ± 0.06
b
a,b
: Values within a row with dierent superscripts dier signicantly at P<0.05, characterizing a
group eect.
A,B
:Values within a column with dierent superscripts dier signicantly at P<0.05,
characterizing a period eect. LP: late pregnancy; EL: early lactation
Metabolic Indicators of Subclinical Ketosis in Ouled Djellal Ewes / Bouzenzana et al. _______________________________________________
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Association of biochemical parameters with the occurrence of SCK
BHB value increased signicantly in both groups of SCK compared
to the healthy ewes groups. A signicant decrease in glucose and
TGs concentrations only in subclinical pregnant toxemic ewes (SPT)
were showed. Cholesterol followed the same behavior as glucose
and TGs and the lowest values were reached during early lactation
in SCK ewes (TABLE III).
The AUC for glucose was 70.7%, and the optimum cut–off point was
2.22 mmol·L
-1
(SE: 40.85% and SP: 100%), and the AUC for cholesterol
was 78.9%, and the optimum cut–off point was 1.55 mmol·L
-1
(SE:
80.28% and SP: 64.86%) (TABLE IV).
The enzymatic activities of AST, ALP, and CK were signicantly higher
in both SCK groups than in the control groups. Whereas, the enzymatic
activities of ALT, GGT, and LDH were signicantly greater only in SPT
ewes than in the healthy late pregnant ewes. Furthermore, the enzymatic
activities of AST, ALT, GGT, ALP, CK, and LDH were highest in recently
lambed ewes with SCK compared to SPT ewes (TABLE III).
The AUC for AST was 84.4%, and the optimum cut–off point was
94.19 UI·L
-1
(SE: 74.65% and SP: 83.78%), and the AUC for ALP was
85%, and the optimum cut–off point was 123 UI·L
-1
(SE: 77.46% and
SP: 81.08%). The AUC for CK was 73.7%, and the optimum cut–off
point was 99.43 UI·L
-1
(SE: 53.52% and SP: 91.89%) (Table IV).
Lower levels of Ca, Mg, Na, and K were observed in ewes with
SCK, either in late pregnancy or early lactation, compared to healthy
ewes. However, P increased signicantly in SPT ewes, followed by a
signicant decrease in recently lambed ewes with SCK (TABLE III).
The AUC for Ca was 94.4%, and the optimum cut–off point was
2,02 mmol·L
-1
(SE: 77.46% and SP: 100%). For K, the AUC was 79.3%,
and the optimum cut–off point was 4.1mmol·L
-1
(SE: 71.83% and SP:
75.68%). (TABLE IV).
The study found that the mean blood BHB levels were 0.7 ± 0.0 mmol·L
-1
in healthy ewes and 1.5 ± 0.0 mmol·L
-1
in SCK groups, where the values
ranging from 0.9–2.3 mmol·L
-1
. Besides, hypoglycemia (<2.22 mmol·L
-1
)
was observed in ewes with SPT. These ndings align with previous
studies [22, 23]. Dietary restriction, lack of gluconeogenic precursors
leading to NEB, and mobilization of body reserves, can explain the
increased BHB levels during the transition period [7]. Thus, BHB < 0.8
mmol·L
-1
indicates a good transition, while BHB > 0.85 mmol·L
-1
is a sign
of energy deciency in ewes [24]. Appropriate nutritional management
can maintain metabolic proles within physiological ranges [16].
Hyperketonemia causes hypoglycemia by inhibiting
gluconeogenesis, glucose uptake and utilization, reducing food intake,
increasing lipolysis, and creating a vicious cycle [6, 25]. This cycle
is further amplied in late pregnancy, as ewes may have a reduced
capacity to utilize BHB as an energy source, contributing to the higher
incidence of pregnancy toxemia (PT) during this period [25]. Insuline
secretion, may have potential inhibitory role of ketogenesis and
regulating role in the utilization of ketone bodies, and uptake of BHB
as well as acetate [26]. Lipotoxicity of NEFAs on the function of β–
pancratic cells compromises insulin production [9]. Hypocalcemia
observed in SCK ewes may increase the depressive action of ketone
bodies on gluconeogenesis [27]. This study found that 100% of SCK
ewes also exhibited subclinical hypocalcemia, highlighting this close
association. Measuring both Ca and BHB levels is crucial for accurate
differentiation and diagnosis [13]. Early lactation creates NEB [16],
conrmed by increased BHB in the study ewes. SCK occurs due
to the energy demand for high milk yield exceeding dietary intake,
leading to body reserve mobilization and increased NEFAs [26]. Insulin
resistance during early lactation increases lipolysis and hepatic
ketogenesis [1, 26]. Thus, hyperketonemia and hypoglycemia indicate
early SCK and NEB, reecting maternal energy deciency in Ouled
Djellal ewes [4, 9, 18, 23]. However, Ouled Djelall ewes were more stable
with hyperketonemia, suffering from SCK rather than clinical ketosis
(ck) despite BHB >1.6 mmol·L
-1
. This raises interesting questions about
the unique metabolic adaptation of this breed.
The study found lower levels of TGs and cholesterol in ewes with
SCK. This is consistent partly with some previous studies that
TABLE IV
Optimum cut–o point of metabolic indicators for SCK
Metabolic
indicators
cut–o
Sensitivity
SE (%)
Specicity
SP (%)
AUC
P
(Area=0,5)
Glucose ≤ 2.22 40.85 100.00 70.7 < 0.0001
Cholesterol ≤ 1.52 80.28 64.86 78.9 < 0.0001
ASAT > 94.19 74.65 83.78 84.4 < 0.0001
ALAT > 13.60 63.38 64.86 69.1 0.0003
GGT > 54.73 38.03 89.19 66.9 0.0015
ALP > 123.00 77.46 81.08 85.0 < 0.0001
CK > 99.43 53.52 91.89 73.7 < 0.0001
LDH > 305.00 49.30 89.19 67.1 0.0009
Ca ≤ 2.10 77.46 100.00 94.4 < 0.0001
Mg ≤ 0.72 71.83 81.08 77.1 < 0.0001
Na ≤ 142.00 47.89 91.89 77.7 < 0.0001
K ≤ 4.1 71.83 75.68 79.3 < 0.0001
_____________________________________________________________________________Revista Cientifica, FCV-LUZ / Vol. XXXIV, rcfcv-e34480
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reported increased TGs and decreased cholesterol in ewes with PT
[24, 28]. However, other studies found elevated cholesterol during
SCK induction [7, 29], while some reported no inuence of SCK on
these variables [26]. During late pregnancy feed restriction, plasma
TGs, VLDL–TGs and VLDL secretion decrease due to reduced liver
VLDL synthesis capacity, causing TGs accumulation in ketotic ewes
[21, 29]. In clinical PT, reduced cholesterol suggests compromised
hepatic lipoprotein secretion inducing fat accumulation [11, 26].
As SCK reduces appetite [28] and cholesterol follows dry matter
intake [30], NEB links to lower cholesterol [31]. Lower cholesterol
and TGs levels in the present study are signs of hepatic lipidosis
often accompanying ketosis. Thus, NEB may disrupt hepatic lipid
metabolism, resulting in SCK. Lower cholesterol during severe NEB
suggests it may predict energy balance in the transition period. This
highlights the interconnectedness of energy metabolism and lipid
homeostasis during metabolically challenging period like peripartum.
The study found increased activity of liver enzymes AST, ALT, and
GGT in ewes with SCK, consistent with previous studies [21, 22, 32,
33]. However, some studies did not nd changes in AST and ALT in PT
[4, 23, 34]. The elevated liver enzymes may be attributed to hepatic
damage or fatty inltration leading to enzyme leakage, due to NEB
[10]. High ketone bodies cause hepatic oxidative stress, apoptosis,
and inammation [21]. AST may be the best liver function marker
in SCK and indicates early hepatic lipidosis [35]. The reduction in
cholesterol with elevated liver enzymes suggests the liver’s role in
ketosis [28]. Previous studies reported that PT associated with an
elevated level of ALP [10]. The reason of the highest ALP activity in
SCK Ouled Djellal ewes could be a negative effect of NEB on hepatic
tissue and consequently resulted in rise of ALP activity originating
from the liver [31]. Plasma LDH and CK activities also increased in SCK
ewes and highest in clinical ketosis [22, 32, 33], indicating possible
muscle damage [37]. Elevated AST and CK suggest muscle protein
mobilization due to NEB [34] or insucient protein intake [11]. AST
elevation may also be due to fatty inltration in kidneys and heart, and
CK elevation indicates muscle degeneration [36]. High CK in PT could
relate to cardiac and skeletal muscle lesions due to lipotoxicity and
oxidative stress from hyperketonemia [36, 37]. This is supported by
the correlations between cardiac markers used to assist diagnoses
of an acute myocardial infarction as CK–MB, troponin I and BHB [36,
37]. Increased AST, CK and LDH in the periparturient period may
indicate reversible myocardial and skeletal muscle damage from
subclinical hypocalcemia associated with SCK, as increased cardiac
biomarkers suggest myocardial damage in parturient paresis [38].
Therefore, elevated AST and CK, along with hypocalcemia, may serve
as critical diagnostic indicators of SCK in Ouled Djelall ewes, related to
the pathogenesis involving cardiac, skeletal muscle lesions, NEB, and
muscle protein catabolism. LDH increases may reect liver, skeletal
and cardiac muscle damage, indicated by increased AST and CK
[33], though LDH is not an early SCK indicator in this study. Overall,
elevations in AST, ALT, GGT, ALP, CK, and LDH can suggest that SCK
in Ouled Djellal ewes may have broader metabolic impacts extending
beyond the liver to involve muscle tissue, potentially including cardiac
muscle. It’s essential to interpret these ndings in conjunction with
other clinical signs, BHB levels, and the overall context of the animal’s
health status to arrive at an accurate diagnosis.
Hypocalcemia was observed in SCK ewes during late pregnancy
(associated with hypomagnesemia and hyperphosphatemia) and early
lactation (with hypomagnesemia and hypophosphatemia). This aligns
with some previous studies [39] but contrasts others [22, 38]. The
hypocalcemia may be attributed to increased fetal calcium demands
[39], colostrum production [34], reduced feed intake [34, 35], or
fatty liver impairing vitamin D hydroxylation [30]. Hypocalcemia
and NEB are connected, with most natural PT cases associated with
hypocalcemia [27]. Hypophosphatemia in early lactation may be
due to hyperparathyroidism increasing urinary phosphorus loss to
compensate for hypocalcemia, and increased phosphorus demands
for milk production [34]. Hypomagnesemia is linked to enhanced
lipolysis in PT [40]. Hypokalemia and hyponatremia were observed,
likely due to reduced feed intake, dehydration, urinary losses from
ketoacidosis, and impaired renal reabsorption [34]. Hypokalemia
indicates metabolic acidosis and is a prognostic indicator for ketosis
severity [22], also a good diagnostic indicator for SCK in Ouled Djellal
ewes. Consequently, SCK caused electrolyte and mineral disturbances
attributed to starvation, renal losses from ketoacidosis or renal
damage, and impaired regulatory mechanisms [5, 34]. This study
revealed signicant electrolyte and mineral imbalances in Ouled
Djellal ewes with SCK, further highlighting the role of kidney in the
pathogenesis of ketosis.
CONCLUSION
Ketonemia characterized by elevated BHB levels, is an essential
feature of SCK in Ouled Djelall ewes, reecting NEB and inadequate
long–term feeding. Twin pregnancy and low body condition score
(BCS < 2.5) were major risk factors for SCK due to NEB. Signicant
changes of energetic, enzymatic and mineral metabolites reveal the
involvement of the liver, kidney, and heart in ketosis pathogenesis,
its impact on electrolyte and mineral balance, and suggest systemic
and complexity of the disease.
Recommendations
Preventing ketonemia is essential to improving animal health,
welfare, and productivity. Feeding ewes according to their energy
and protein requirements during the periparturient period while
monitoring BHB and BCS, especially in twin–bearing ewes, is
recommended to prevent ketosis.
Metabolic Indicators of Subclinical Ketosis in Ouled Djellal Ewes / Bouzenzana et al. _______________________________________________
6 of 7
Ethical Statement
This study received approval from the Institutional Animal Care
Committee of the National Administration of the Algerian Higher
Education and Scientic Research (Approval no: 98–11, Law of August
22, 1998).
Conict of Interest
The authors declared that there is no conict of interest.
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