Bull Vet Inst Pulawy 50, 93-96, 2006
RELATIONSHIP BETWEEN VITAMIN A
AND β-CAROTENE LEVELS
DURING THE POSTPARTUM PERIOD
AND FERTILITY PARAMETERS IN COWS
WITH AND WITHOUT RETAINED PLACENTA
YASAR AKAR1 AND ABDULLAH GAZIOGLU2
1
Department of Obstetrics and Gynaecology, 2Department of Internal Medicine,
Faculty of Veterinary Medicine, Firat University, 23119 Elazig, Turkey
e-mail: [email protected]
Received for publication April 15, 2005.
Abstract
Serum vitamin A and β-carotene levels were ascertained in
cows with and without retained placenta during 2-6 weeks
postpartum and their relationship to fertility parameters were
studied. Twenty cows with retained placenta and 20 controls
were examined. In cows with retained placenta, serum vitamin
A values were significantly lower in the 2nd week after
parturition when compared with the other weeks. In the control
group, the values were significantly higher the 6th week than
those in the 2nd and 4th weeks. Serum vitamin A level in the
retained placenta group was significantly lower than that in the
control group in the 3rd, 5th and 6th weeks. Serum β-carotene
levels increased gradually in both groups after parturition.
Values for the retained placenta cows were significantly lower
than in the controls throughout the postpartum period. The
calving to the first oestrus and calving to conception intervals
were considerably longer in the retained placenta group, but
statistically no significant differences were found between the
groups in terms of calving to conception interval, services per
conception, the first service conception rate, and total
pregnancy rate. It was concluded that poor fertility parameters
in cows with retained placenta, as compared to the control
group, could relate to the low content of vitamin A and
especially β-carotene.
Key words: cow, retained placenta, vitamin A, βcarotene, fertility.
Retained placenta (RP) is an important postpartum
disease in dairy cows with a frequency range between
2% and 69% (1, 5, 22). Various causes of RP have been
identified i.e. uterus atony, abortions, late or premature
birth, dystocia, twinning, deficiency in vitamins A and
E, β-carotene and selenium, etc. (1, 22). RP causes a
decrease in milk yield; creates additional expenses for
animal owners and also reduces fertility by increasing
the likelihood of metritis (1).
In cows, normal vitamin A level is 25-80 µg/100 ml,
subnormal level - 7-12 µg/100 ml, and values below 7
µg/100 ml represent deficiency. β-carotene normal level
is 300-1 200 µg/100 ml, subnormal level - 100-200
µg/100 ml and level of 9-100 µg/100 ml is regarded as
deficiency (6, 24). Cows fed green fodder have serum βcarotene and vitamin A levels during the summer
months (June-July) considerably higher than in other
months. Also, a relationship between the levels of serum
vitamin A and β-carotene, and feeding sources and
seasons was established (3, 7, 22).
Vitamin A is an essential vitamin for sight, bonemuscle growth, protection of the integrity of epithelial
cells, immune cell functions, gene arrangement, and
normal reproductive activity in cows (9, 11, 13, 14). The
clinical signs of vitamin A deficiency towards the end of
pregnancy are abortion, RP, night blindness, diarrhoea
and an increase in the number of dead, blind, weak and
sick calves (11, 14, 27). Persistence of vitamin A
deficiency after parturition may decrease the conception
rate (14). An adult cow needs 76 IU of vitamin A/kg/d
in the diet in order to maintain its normal reproductive
function (27).
β-carotene, the precursor of vitamin A, shows
antioxidant effect and influences reproductive and
thyroid functions (24, 27). One mg of β-carotene is
equivalent to 400 IU of vitamin A (3, 12, 13, 24, 27). βcarotene deficiency in cows prolongs the oestrus period,
delays ovulation, increases abortions and early
embryonic death rates, weakens the oestrus signs,
increases ovarian cysts, RP and metritis risk, increases
delivery rates of dead, weak, and blind calves and
reduces fertility (4, 8, 11, 13, 14, 24). An adult cow
needs 0.18 mg of β-carotene/kg/d in order to maintain its
normal reproductive functions (13, 27).
The corpus luteum contains a high level of βcarotene (12-14). However, it does not contain vitamin
A and low fertility is related to a low level of β-carotene.
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Hurley and Doane (14) reported that a high β-carotene
level influenced the release of ovarian steroids. On the
other hand, other researchers (11) reported that βcarotene stimulated LH secretion from the hypophysis
and thus increased progesterone production. Dunn and
Moss (8) showed high vitamin A and 17-β oestradiol
concentrations in normal follicles compared to tiny and
atretic follicles, and suggested that this was a sign of the
survival of the follicle.
In this study, serum vitamin A and β-carotene levels
in cows with or without RP were examined during the
postpartum period and their relationship to fertility
parameters was studied.
observed until day 120 postpartum and those that were
not pregnant were considered infertile.
Vitamin A and β-carotene levels were compared by
paired t-test within each group, whereas these values
between groups were compared by independent Student
t-test. Calving to the first oestrus, calving to the first
service and calving to conception intervals were
compared by independent Student t-test; the services per
conception, the first service, and total pregnancy rates
was compared by Chi-square test (26). These analyses
were made with SPSS (25).
Results
Material and Methods
The study was performed on 40 Brown Swiss breed
cows, aged 2-6 years, at the research and practice farm
of Firat University. The animals that were unable to
discharge foetal membranes totally or partially within 24
h postpartum were considered to have RP (20 cows),
while those that could discharge all the membranes were
considered the control group (20 cows). All the cows
were in the same barn and fed the same diet.
Jugular vein blood samples were collected into
sterile containers between January to May, 2002. Ten
milliliter of the blood was collected from all cows on
days 14, 21, 28, 35 and 42 postpartum. The blood was
centrifuged at 3000 r.p.m. for 20 min and sera were
placed into sterile tubes and then frozen at –20°C. Serum
vitamin A and β-carotene levels were measured using
spectrophotometric method (Schimadzu UV-1208, UVVIS spectrophotometer).
The cows were examined rectally three times per
week from week 2 postpartum until the first service, and
their ovarian activity was recorded. Cows were
inseminated at each oestrus detected on day 45 or later
and pregnancy was determined by ultrasound
examinations 35 d after the service. The animals were
The serum vitamin A values are given in Table 1. In
the RP group, vitamin A level on day 14 was
significantly lower (P<0.05) compared to the other days.
In control group, vitamin A level was significantly
higher at day 42 postpartum compared to days 14 and 28
(P<0.05). In both groups, the serum β-carotene levels
increased considerably (P<0.05) on the succeeding days
after the parturition (Table 2).
The comparison of serum A vitamin levels between
the both groups (Table 1) indicates that while there were
no differences in vitamin A levels on days 14 and 28
postpartum between cows with and without RP, the
levels on days 21, 35 and 42 were significantly higher in
the control group (P<0.05, P<0.01, P<0.01,
respectively). On all days postpartum, the β-carotene
levels of the control group were statistically higher than
those in the group with RP (P<0.05 or P<0.01) (Table
2).
Table 3 shows the fertility parameters of control and
RP cows. The calving to the first oestrus and calving to
the first service intervals were considerably longer in the
group with RP (P<0.05). Regarding other fertility
characteristics, no differences were found between
control and RP group (P>0.05).
Table 1
Vitamin A levels (µg/dl) in cows with and without RP
Postpartum days
14
21
28
35
42
RP (n:20)
38.49±2.07b
43.69±2.07a
44.65±2.22a
44.23±1.87a
46.30±2.00a
C (n:20)
51.92±2.60b
54.10±2.85ab
53.16±2.92b
55.47±3.24ab
60.45±2.98a
P
*
**
**
a,b,c,d
: the group average difference represented by different letters in the same line is significant (P<0.05).
- P>0.05; * P<0.05; ** P<0.01.
Table 2
β-carotene levels (µg/dl) in cows with and without RP
Postpartum days
14
21
28
35
42
d
c
bc
b
RP (n:20)
11.24±0.88
13.18±1.44
14.84±1.64
16.26±1.46
19.38±1.77a
d
c
c
b
C (n:20)
14.11±0.97
24.38±3.83
34.42±7.09
50.93±11.11
54.57±10.94a
P
*
**
**
**
**
a,b,c,d
: the group average difference represented by different letters in the same line is significant (P<0.05).
* P<0.05; ** P<0.01.
95
Table 3
The fertility parameters of cows with and without RP
Fertility parameters
RP (n:20)
C (n:20)
Calving to first oestrus interval (d)
50.06±6.36
31.50±2.33
Calving to first service interval (d)
81.00±4.93
62.38±4.88
Calving to conception interval (d)
73.86±10.34
95.60±7.51
Services per conception
1.4
1.3
First service pregnancy rate (%)
53.33
62.50
Total pregnancy rate (%)
65.55
70.00
- P>0.05; * P<0.05.
Discussion
It is well known that vitamin A and β-carotene
deficiency causes negative impacts on fertility and
increases RP incidence in cows. In addition, abortion,
night blindness, increase in the birth of weak and sick
calves, weakening the oestrus symptoms, and delay in
ovulation are other negative outcomes related to
deficiency of vitamin A and β-carotene (4, 13, 14, 24,
27). To the authors knowledge, the current study is the
first to provide information on the vitamin A and βcarotene level during postpartum period and its
relationship with fertility parameters in cows with and
without RP.
Ineba et al. (15) found that there was no significant
difference in plasma vitamin A levels between Holstein
cows with and without RP when measured on the day of
parturition and one day postpartum, but the plasma βcarotene levels were significantly lower in cows with
RP. Ishak et al. (16) reported that vitamin A and βcarotene levels were 31.4 – 33.1 and 212 - 209 µg/100
ml in cows with and without RP, respectively, and the
difference between the groups was not significant. Other
authors (23) reported that vitamin A and β-carotene
administration to Holstein cows before parturition had
no effect on postpartum vitamin A and β-carotene levels.
The mean serum vitamin A and β-carotene levels at
parturition and 3 and 4 weeks postpartum were 1 100, 1
300, 1 400 and 300, 400, 400 µg/100 ml, respectively.
Graves-Hoagland et al. (12) demonstrated that plasma
vitamin A and β-carotene levels at oestrus cycles
initiated 30-49 d postpartum were 36 µg/100 and 277.4
µg/100 ml. Michal et al. (21) administered vitamin A
and β-carotene to Holstein cows 4 weeks before calving
and found that the mean serum contents of the
compounds were 1.6 and 4.3 µmol/l before
supplementation, decreased at parturition in all cows,
including the controls, and tended to increase 1, 2, and 4
weeks postpartum. Johnston and Chew (19) reported
that in non-mastitic cows, plasma vitamin A and βcarotene concentrations were decreased at calving (31
and 230 µg/100 ml), but their levels increased 1, 2, and 4
weeks postpartum. Also, plasma β-carotene levels in
cows decreased in winter compared to the summer
months; the levels also decreased during pregnancy,
being the lowest during the last months of pregnancy
and started to increase with the start of lactation (3). Can
et al. (6) found that there was no difference in vitamin A
P
*
*
-
levels in infertile cows whether housed or at pasture, but
β-carotene levels were significantly lower in housed
cows. These findings agree with the previous studies
which generally report a decrease in vitamin A and βcarotene levels at calving and thereafter an increase in
their levels in the postpartum weeks (3, 19, 21).
However, our results disagree with the results of the two
previous works, which found no difference for the
mentioned parameters one day postpartum (16, 23). The
low levels of vitamin A and β-carotene in both groups in
our trial were thought to be due to the collection of
blood samples in the winter months.
Several authors have suggested that vitamin A and βcarotene supplementation have some beneficial effects,
including stronger oestrus symptoms, decreased
incidence of luteal cysts, decreased services per
conception, shortening of calving to the first oestrus and
calving to conception intervals and increase in total
pregnancy rate (9, 13, 14, 17, 18, 27). It was reported
that the pregnancy rate following the first insemination
was 48.6% and there was no significant association
between this rate and serum vitamin A or β-carotene
levels in dairy cows (20). The other authors (16)
reported that vitamin A supplementation had no effect
on the incidence of RP and did not improve the
reproductive parameters. They also noted that services
per conception were 3.08 for controls and 2.2 for
supplemented cows; the intervals from calving to
conception were 122 and 129 d for controls and
supplemented cows, respectively. It was reported that
vitamin A and β-carotene supplementation before or
after calving had no effect on calving to the first service
interval in cows. However, it was demonstrated that
only β-carotene supplementation had adverse effects on
calving to conception interval, services per conception,
pregnancy rate for the first service and total pregnacy
compared to the supplementation of only vitamin A, or
their combination (10). Akordor et al. (2) found that
prepartum β-carotene supplementation had no positive
impact on the fertility of Holstein cows. Calving to the
first oestrus interval, calving to the first service, services
per conception and rate of conception for the first
service for cows receiving β-carotene supplementation
versus controls were 47-44, 77-73, 97-82 d, 1.63-1.87
and 54 - 54%, respectively (2). In the present study,
calving to the first oestrus and calving-first service
intervals were significantly increased in cows with RP.
The findings that poor fertility and lower vitamin A and
96
β-carotene levels occurred in cows with RP were
controversial to the above mentioned literature.
In conclusion, serum vitamin A and β-carotene levels
increased gradually postpartum in cows both with and
without RP, but their levels were significantly lower in
cows with RP compared to the control group. It was
thought that the low fertility observed in cows with RP
was associated with the deficiency of vitamin A and βcarotene. Additionally, it seems that the observed low
levels of β-carotene and vitamin A in all the cows were
due to lack of green fodder in animal diet.
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