Key words : progesterone, overt, estrus, estrus,
expression, silent, estrus, cow
Poor expression of estrus is one of the major factors that
hamper efficient utilization of tropical Sahiwal cows. Estrus
is traditionally observed by behavioural symptoms which, however,
are practically impossible to observe or monitor in situations
where herd size is large and animals are stallfed. Heat detection
is also very difficult due to lack of expert personnel, variation
of duration of estrus and reluctance of some teaser bulls
to mate. Progesterone serves as a marker for determination
of functional status of corpus luteum and as a diagnostic
tool for identifying ovarian condition such as estrus confirmation,
silent estrus and lack of cyclicity (3, 5, 8). Progesterone
at appropriate level is essential for expression of estrus,
preparing the uterus for implantation and maintenance of pregnancy
(12). There is no information available on peripheral plasma
progesterone concentration in relation to expression of behavioural
estrus symptoms in Sahiwal cows. The present study was, therefore,
undertaken to measure peripheral progesterone concentrations
during estrous cycle and to relate them to occurrence of overt
or silent estrus in Sahiwal cows.
Experimental animals and blood sampling
Three healthy Sahiwal cows were selected
from the animal herd of National Dairy Research Institute
and maintained under standard feeding and management schedule
as practised in the herd. Blood samples were collected daily
through jugular venepuncture for 32 consecutive days during
the winter months of January and February. Blood samples
were centrifuged at 3000 rpm for 30 min. Plasma was harvested
and stored in deep freeze at -20°C for analysis
of progesterone. The animals were kept in loose housing system
and checked for manifestation of estrus twice daily (8A.M.
and 6P.M.) by using vasectomized bull, palpation
of reproductive organs per rectum and confirmed by plasma
Progesterone was estimated by a simple,
direct radio-immunoassay developed in our laboratory (9).
The sensitivity of the assay was 8 pg/tube. The intra- and
inter-assay coefficients of variation were 13.4 and 16.9%,
respectively (n = 6). The progesterone antiserum (anti-progesterone-
11 alpha-hemisuccinate- BSA) crossreacted 4 pregnane-3, 20
diene, 11 alpha-hydroxyprogesterone and corticosterone to
the extent of 100, 110 and 0.2%, respectively The crossreactivity
of the antiserum with cortisone, hydrocortisone was less than
0.01% and with b-estradiol, estriol and testosterone was less than 0.001%.
For statistical analysis, the estrous cycle was divided into
4 phases namely late luteal (day - 4 to day - 2, day 0 = day
of estrus), periestrus phase (day - 1 to day 1), early luteal
phase (day 2 to day 5) and midluteal phase (day 6 to day 14).
The changes in peripheral plasma progesterone concentrations
during different phases of the cycle in cows that exhibited
both overt and silent estrus were analysed by Analysis of
Out of a total of five estrus, three were accompanied by overt
signs whereas the remaining two were silent estrus. The plasma
progesterone concentrations in cows that exhibited overt estrus
behaviour and those that showed silent estrus during different
days of cycle are depicted in Fig. 1. The mean (±S.E.M.) plasma
progesterone concentrations were 0.40 ± 0.02 and 0.40±0.03
ng/ml on the day of estrus and rose to a peak level of 3.03
± 0.91 and1.75 ± 0.35 ng/ml on day 10 and day
8 which then declined gradually to the basal level on the
day of next estrus in cows that exhibited overt signs and
silent estrus, respectively. These results are in agreement
with earlier reports in cows (6, 14) and buffaloes (1, 2,
13) in terms of minimum level on the day of estrus with gradual
rise to the higher levels during luteal phase and then declining
to basal level at subsequent estrus. Stabenfeldt et al. (17)
reported that progesterone levels ranged from less than 0.5
ng/ml during follicular phase to 6.6 ng/ml at peak luteal
phase in cows. Progesterone levels increased rapidly from
day 3 to day 8 with much slower rate of increase from day
8 to 17 indicating a cyclic pattern of progesterone concentration
in plasma of cows. A cyclic pattern of progesterone in nonpregnant
cows with 7.5-10 ng/ml during luteal phase and 1-2 ng/ml for
4 to 6 day period around the time of ovulation was reported
by Gupta and Pope (6). In another study a cyclic pattern
of progesterone in ovarian venous blood of cows was found
with peak concentration on about day 16 followed by a decline
on day 17 till ovulation (4).
Fig. 1: Peripheral plasma progesterone concentration during
overt and silent estrus in Sahiwal Cows.
The cyclic pattern of progesterone concentrations in jugular
plasma is in agreement with known changes in corpus luteum
function in cow during estrous cycle. The decline of progesterone
in plasma of cows towards the end of the cycle as well as
a marked rise during the time of corpus luteum development
suggests that corpus luteum functioning can be monitored in
plasma by progesterone determination. The functional
activity of bovine corpus luteum was reported to be increased
by about day 15 and then declined as reflected from decrease
in corpus luteum weight and progesterone concentration in
cows (10). It has been reported that the net progesterone
content increased progressively from day 2 (17 mg/gm) to day 11
(136 mg/gm) and remained relatively constant
(150 mg/gm) upto day 20 and thereafter fell
(46 mg/gm) at day 0 (7). Corpus luteum weight
increased from early to midluteal phase corpus luteum and
declined in the late luteal phase in Surti buffaloes as is
shown in previous study (15). Corpus luteum extract progesterone
was significantly (P<0.01) higher in midluteal corpus luteum
compared to other luteal phases. A previous study has shown
that corpus luteum weight rose progressively from 605 mg on
day 3 to 1885 mg on day 13 followed by a decline to 1292 mg
on day 18 in Surti buffaloes. The progresterone concentration
was 34.5 mg/gm on day 3 rising to 62 mg/gm on day 13 and lowest concentration of 32.3 mg/gm on day 18 (11). The mean (±S.E.M.) progesterone levels
in cows that exhibited overt estrus and those in silent estrus
during different phases of cycle are shown in Table 1. Plasma
progesterone concentrations increased from 0.40 ± 0.02 ng/ml
during periestrus phase to 0.74 ± 0.10 ng/ml during
early luteal phase and then further (P<0.05) to 1.94 ±
0.22 ng/ ml during midluteal phase following which declined
(P<0.05) to 0.63 ± 0.16 ng/ml during late luteal phase
in cows exhibited overt estrus. In cows that exhibited silent
estrus plasma progesterone concentrations increased from 0.47
± 0.03 ng/ml during periestrus phase to 0.94 ± 0.08 ng/ml
during early luteal phase and then further (P<0.05) to
1.39 ± 0.13 ng/ml during midluteal phase following which declined
to 0.95 ± 0.19 ng/ ml during lateluteal phase. The overall
mean (±S.E.M.) plasma progesterone levels in cows that exhibited
overt estrus was 1.23 ± 0.99 ng/ml as against 1.08 ± 0.09
ng/ ml in silent estrus. It was concluded that plasma progesterone
levels were lower (P>0.05) in cows that exhibited silent
estrus compared to overt estrus and might be responsible for
poor expression of estrus.
Table I: Plasma progesterone concentration (ng/ml) during
different phases of cycle in cows exhibited overt and
We thank Director, NIANP for providing the facility for preparing
the manuscript. S. Mondal was supported by Junior NDRI fellowship.
Technical assistance rendered by Mr. P. C. Singh and Mrs.
A. Ladkhani is acknowledged.
A, Agarwal SP, Agirwal VK, Rehman SA, Laumas KR. Steroid
hormones. Part II. Serum progesterone concentration in buffaloes.
Ind J Expt Biol 1977; 15: 591-593.
NK, Arora RC, Prasad A, Pandey RS. Plasma levels of gonadal
hormones in cycling buffalo heifers. Ind J Expt Biol 1979; 17: 823-825.
R, Karg H, Zwiauer D, Butler IV, Pirchner F, Rattenberger
E. Analysis of factors influencing reproductive performance
of the dairy cows by progesterone assay in milk fat. Br
Vet J 1983; 139: 29-37.
W, Stupnicka K, Donianski E. Progesterone levels in ovarian
venous blood during the estrous cycle of' the cow. J Reprod
Fertil 1968; 15:409-414.
RH, Oltenacu EAB, Kiminerfeld HL, Smith RD, Rick PM, Braun,
RK. Milk progesterone as diagnostic aid. Br Vet J 1979;
Pope GS. 1968. Variation in the level of progesterone in
the systemic plasma of the cow. J Endocr 1968; 40:
HD, Armstrong DT. Corpus luteum growth and progesterone synthesis
during the bovine estrous cycle. Anim Sci 1968; 27:
B, Gunzler O, Hamburger R, Schmidt W. Milk progesterone as
a parameter for fertility control in cattle : methodological
approaches and present status of' application in Germany.
Br Vet J 1976; 1:32: 469-476.
M, Prakash BS. Relationship of progesterone in plasma and
whole milk of buffaloes during cyclicity and early pregnancy.
Trop Anim Hlth Prod 1993; 25: 185-192.
SE, Zimbelman RG and Casida LE. Variation in progesterone
content of the bovine corpus luteum of the estrous cycle.
J Anim Sci 1962; 21: 266-271.
GN, Buch NC, Patel BM.
A study of follicular and luteal characteristics of the ovary
at different stages of estrous cycle in Surti buffalo heifer.
J Reprod Fertil 1971; 27: 301.
S, Palta P, Prakash BS. Influence of season on plasma progesterone
levels in cycling Murrah buffaloes. In : Proceedings of
29tli British Congress of Obstetrics and Gynaecology,
GS, Pandey RS. Gonadal steroid hormone concentration in blood
plasma and milk of' primiparous and multiparous pregnant and
non pregnant buffaloes. Theriogenotogy 1983; 19: 491-505.
DW, Condert SP, Short RV. Effects of bovine LH and human
chorionic gonadotropin on the bovine luteum in vivo. J
Reprod Fertil 1967; 14:277-285.
RG, Mehta VM, Correlated behaviour of blood and corpus luteum
progesterone levels with luteal cell types in Surti buffaloes.
Buff J 1992; 8: 167- 173.
GW, Cochran WG. In : Statistical Methods. 1967;
6th Edn. Oxford and 1BH Publication Co, New Delhi, India.
GH, Ewing LL, McDonald LE. Peripheral plasma progesterone levels
during the bovine estrous cycle. J Reprod Fertil 1969;