www.elsevier.comrlocaterapplanim
Short communication
A note on silent ovulation identified by using
radiotelemetry for estrous detection
Milan P. Shipka
)Department of Plant, Animal and Soil Sciences, UniÕersity of Alaska Fairbanks, Fairbanks, AK 99775-7200, USA
Accepted 18 August 1999
Abstract
Ž .
This study was undertaken to determine the occurrence of silent ovulation SO in
high-produc-Ž .
ing, postpartum PP Holstein cows. Nineteen high-producing, multiparous cows received
trans-Ž w
. Ž .
mitters Heatwatch , DDX, Denver, CO for radiotelemetry RT and began visual estrus
Ž .
detection VED routine for 1r2 h twice daily, on day 10 PP. Blood samples were obtained every
Ž .
other day commencing on day 10 PP, for RIA of progesterone P . Following P assay, RT and4 4
VED data were evaluated at time periods coinciding with ovulation to determine whether standing
Ž .
estrus had occurred. First ovulation occurred at 29.1"3.0 days PP range 17–69 days compared
Ž . Ž
to first mount at 39.6"4.0 days PP range 17–69 days and at 47.6"3.6 days PP range 24–77
.
days for RT and VED, respectively. VED indicated 94.7% of first ovulations as SO while the inclusion of RT with VED indicated that only 42.1% of first PP ovulations were true SO. During
Ž .
second PP ovulations ns16 , VED indicated 50% SO while the inclusion of RT indicated only
Ž .
12.5% true SO. During third and fourth PP ovulations ns15 , VED indicated 33.3% SO while the inclusion of RT indicated only 6.7% true SO. When RT was associated with ovulation, there
Ž
were fewer mounts at first PP ovulations compared to subsequent ovulations 1.1"0.1 vs.
. Ž
3.8"0.7, P-0.0005 and lengths of individual mounts were shorter 2.6"0.5 vs. 3.4"0.3 s,
.
P-0.05 . Previous studies have indicated the majority of first PP ovulations to be SOs. However, it appears more likely that while a substantial number are SOs, more are associated with a reduced expression of behavioral estrus.q2000 Elsevier Science B.V. All rights reserved.
Keywords: Estrous behavior; Silent ovulation; Silent estrus; Radiotelemetry
)Tel.:q1-907-474-7429; fax:q1-907-474-6184; e-mail: ffmps@uaf.edu
0168-1591r00r$ - see front matterq2000 Elsevier Science B.V. All rights reserved.
Ž .
1. Introduction
The expression of estrous behavior is brought about by high systemic concentrations
Ž .
of estrogens produced by the pre-ovulatory follicle for review, see Allrich, 1994 which
Ž
stimulates this behavior coincident with the ovulatory LH surge Walton et al., 1987;
. Ž .
Rajamahendran and Taylor, 1991 . The occurrence of silent ovulation SO , ovulation
Ž .
without the expression of estrous behavior, during the postpartum PP period is common among high-producing dairy cows. Documentation of SO has been based on endocrine assay and visual observation, including videotaping, combined with additional information provided by techniques such as rectal palpation, the use of marker animals,
Ž
animal activity, and milk temperature measurement King et al., 1976; Kennedy and
. Ž .
Ingalls, 1995; Gil et al., 1997 . Kyle et al. 1992 indicate that 50% to 80% of first ovulations are SO. The question remains whether the inability to observe estrous behavior is the result of SO or simply that the behavior occurred but was not seen by the
Ž .
observer. The use of radiotelemetry RT to allow 24 h per day recording of cow mounting activity has been shown to be an effective tool to identify mount acceptance
Ž .
by estrual animals Stevensen et al., 1996; Walker et al., 1996 . The objective of this study was to identify ovulations that were silent by using RT and visual estrus detection
ŽVED to collect estrous behavior data, verifying the occurrence of ovulation using. Ž .
progesterone P4 assay.
Ž . Ž .
Fig. 1. Days from parturition mean"SEM until first ovulation stippled column , first RT recorded mount
2. Materials and methods
Ž
Nineteen high-producing multiparous Holstein cows previous 305 days records
w
. Ž .
xs11,929"384 kg milk received RT transmitters Heatwatch , DDX, Denver, CO and were continuously monitored for mounting behavior beginning on d 10 PP. Continuous observation via RT was carried out on each cow until the occurrence of first AI breeding. All cows were routinely observed for expression of behavioral estrus twice daily by experienced herdspersons for 1r2 h following each milking.
Blood samples were obtained via coccygeal venipuncture every other day at 1200 h commencing on day 10 PP and continuing throughout the period of continuous radio telemetric monitoring. Immediately following collection, blood samples were processed and plasma stored frozen for later assay of P utilizing procedures validated for bovine4
Ž .
plasma Shipka and Ellis, 1996 . Following collection of behavioral data, all plasma samples were analyzed for P in duplicate aliquots, within two assay runs over a 2-day4 period. Sensitivity of the assay was approximately 0.2 ngrml, intra- and interassay CV were 3.9% and 6.9%, respectively.
Systemic P concentrations were used to retrospectively examine each cow’s PP4 ovarian function. First PP ovulation was assumed to have occurred within 4 days prior to the first sustained increase in systemic P above 1.0 ng4 rml. Subsequent ovulations were
Ž . Ž .
Fig. 2. Percent of first cross-hatched columns , second stippled columns , and combined third and fourth
Ž .
assumed to have occurred during any period of nadir P4 -1.0 ngrml following a period of sustained elevated P .4
Ž .
Analysis of variance followed by Bonferroni comparison MSD was used to compare PP time periods until first ovulation, first mount recorded by RT and first
Ž .
mount recorded by VED Snedecor and Cochran, 1980 . Student’s t-test was used to compare length of individual mounts occurring at first and subsequent ovulations as well as to examine differences in the number of mounts associated with ovulation when
Ž
mounting behavior was recorded by RT at the time of ovulation Cochran and Cox,
.
1957 .
3. Results
Ž .
Length of time PP until first ovulation indicated by P4 range 17–69 days , first RT
Ž . Ž .
recorded mount range 17–69 days ; and first VED recorded mount range 24–77 days
Ž . Ž
Fig. 3. Comparison means"SEM of number of mounts and length of individual mounts at first black
. Ž .
Ž .
were all different P-0.01, F2,18s7.48, MSDs3.6; Fig. 1 . Percent of ovulations characterized as SO by VED and RT are illustrated in Fig. 2. Standing behavior was not
Ž .
observed by VED at 94.7% of first ovulations ns19 . RT recorded at least one mount coinciding with 11 of 19 first ovulations indicating that only 42.1% were true SOs.
Ž .
During second PP ovulations ns16 , standing behavior was not observed by VED at 50% of ovulations while RT indicated at least one mount coinciding with 14 of 16 ovulations, indicating only 12.5% true SOs. During third and fourth PP ovulations
Žns15 standing behavior was not observed by VED at 33.3% of ovulations, while RT.
indicated at least one mount coinciding with 14 of 15 ovulations indicating only 6.7%
Ž . Ž .
true SOs. Using RT data Fig. 3 , fewer mounts P-0.0005, td fs10s6.548 were associated with first PP ovulation compared to subsequent ovulations and length of
Ž .
individual mounts were shorter P-0.05, td fs10s1.900 at first PP ovulation com-pared to subsequent ovulations.
4. Discussion
This study indicates that while many ovulations are accompanied by estrous behavior, visual observation of the behavior is difficult with standard estrous detection programs. In this study, 62% of the total ovulations during the PP period would have been characterized as SO if VED would have been the only criteria of determination. The inclusion of RT indicated a much lower incidence of true SO, which represented only 22% of the total ovulations. SO is particularly prevalent at the time of the first PP
Ž .
ovulation with estimates ranging from 50% to 94% Kyle et al., 1992; Senger, 1994 . Current information indicates that only 42.1% of first PP ovulation in this group of dairy cows were true SO, but many of those ovulations were associated with fewer mounts accepted by the estrual cow and were of shorter duration than mounts accepted at the time of subsequent ovulations.
Previous information indicates that estradiol effects on estrous behavior are ‘‘all or
Ž .
none’’ Allrich, 1994 which could be a point of conflict between this study and previous studies. Systemic estradiol was not measured in animals on the current study and, therefore, conclusions about the effects of estradiol in this study are not warranted. It is notable, however, that there are definite differences in the intensity of estrous behavior recorded in this study, whether intensity is determined by the total number of mounts accepted by an estrual cow or the length of time an estrual cow will stand for each mount. If estrous behavior is assumed to be an ‘‘all or none’’ response brought about by threshold levels of estradiol, then the difference in intensity of behavior must be the result of some other physiologic mechanism. Estradiol effects on the behavioral centers of the brain — neuronal centers responsible for expression of estrous behavior — might cause varied responses due to such factors as previous steroid hormone
Ž .
exposure Glencross et al., 1981; Davidge et al., 1987; Vailes et al., 1992 or metabolic
Ž
state associated with high levels of milk production and energy balance Butler et al.,
.
1981; Harrison et al., 1989, 1990 .
that the intensity of estrous behavior expression is reduced at first PP ovulation compared to subsequent ovulations.
5. Conclusion
Radiotelemetric estrous detection can be carried out around the clock and is not sensitive to differences in the intensity of estrous behavior expression by an estrual cow. Very low intensity estrous bouts were identified that would have been labeled SO using only visual estrous detection management. Identification of estrous activity during the early PP period, a period associated with a high percent of SO, is important because it helps producers identify cows that have returned to estrous cyclicity. RT may prove to be a helpful management tool for detection of estrous behavior in production settings.
Acknowledgements
This research was supported by the Utah Agricultural Experiment Station, Utah State University, Logan, UT 84322-4810. Approved as journal paper no. 7129.
References
Allrich, R.D., 1994. Endocrine and neural control of estrus in dairy cows. J. Dairy Sci. 77, 2738–2744. Butler, W.R., Everett, R.W., Coppock, C.E., 1981. The relationships between energy balance, milk production,
and ovulation in early postpartum dairy cows. J. Anim. Sci. 53, 742–748.
Cochran, W.G., Cox, G.M., 1957. Experimental Design. Wiley, New York, pp. 100–102.
Davidge, S.T., Weibold, J.L., Senger, P.L., Hillers, J.K., 1987. Influence of varying levels of blood progesterone upon estrous behavior in cattle. J. Anim. Sci. 64, 126–132.
Gil, Z., Szarek, J., Kural, J., 1997. Detection of silent oestrus in dairy cows by milk temperature measurement. Anim. Sci. 65, 25–29.
Glencross, R.G., Esslemont, R.J., Bryant, M.J., Pope, G.S., 1981. Relationships between incidence of pre-ovulatory behavior and the concentrations of estradiol 17band progesterone in bovine plasma. Appl. Anim. Ethol. 7, 141–148.
Harrison, R.O., Young, J.W., Freeman, A.E., Ford, S.P., 1989. Effects of lactational level on reactivation of ovarian function and interval from parturition to first visual oestrus and conception in high-producing Holstein cows. Anim. Prod. 49, 23–28.
Harrison, R.O., Ford, S.P., Young, J.W., Conley, A.J., Freeman, A.E., 1990. Increased milk production vs. reproductive and energy status of high-producing dairy cows. J. Dairy Sci. 73, 2749–2758.
Kennedy, A.D., Ingalls, J.R., 1995. Estrus detection with activity tags in dairy cows housed in tie-stalls. Can. J. Anim. Sci. 75, 633–636.
King, G.J., Hurnik, J.F., Robertson, H.A., 1976. Ovarian function and estrus in dairy cows during early lactation. J. Anim. Sci. 42, 688–692.
Kyle, S.D., Callahan, C.J., Allrich, R.D., 1992. Effect of progesterone on the expression of estrus at the first postpartum ovulation in dairy cattle. J. Dairy Sci. 75, 1456–1460.
Senger, P.L., 1994. The estrus detection problem: new concepts, technology, and possibilities. J. Dairy Sci. 77, 2745–2753.
Shipka, M.P., Ellis, L.C., 1996. Bull presence suppresses postpartum ovarian reactivation in dairy cattle. Proc. WSASAS 47, 225–228.
Snedecor, G.W., Cochran, W.G., 1980. Statistical Methods. Iowa State Univ. Press, Ames, IA, pp. 215–237. Stevensen, J.S., Smith, M.W., Jaeger, J.R., Corah, L.R., LeFever, D.G., 1996. Detection of estrus by visual observation and radiotelemetry in prepubertal, estrus-synchronized beef heifers. J. Anim. Sci. 74, 729–735. Vailes, L.D., Washburn, S.P., Britt, J.H., 1992. Effects of various steroid milieus or physiologic states on
sexual behavior of Holstein cows. J. Anim. Sci. 70, 2094–2103.
Walker, W.L., Nebel, R.L., McGilliard, M.L., 1996. Time of ovulation relative to mounting activity in dairy cattle. J. Dairy Sci. 79, 1555–1561.
