Visual Detection Of Estrus Research Articles

Reproductive performance and serum concentrations of progesterone of heat-stressed Holstein heifers subjected to timed artificial insemination and progesterone supplementation

Sixty-nine Holstein heifers were used to evaluate the effect of progesterone supplementation after timed artificial insemination (TAI) on conception rates of heifers under heat stress. Heifers were randomly assigned to 1 of 3 treatments: 1) control treatment (C), visual detection of estrus. Heifers detected in estrous were inseminated according to the AM-PM procedure (n = 23); 2) TAI (n = 24), using a CIDR device (insert containing progesterone) placed intravaginally on day -10 and removed on day -2 with PGF2α given on day -3. Heifers were given 0.5 mg of ECP at CIDR insertion and a second injection (0.5 mg ECP) was given on day -2 and 48 h after all the heifers were inseminated (day 0); and 3) TAI with progesterone supplementation (TAI+S; n = 22), consisting of TAI plus progesterone supplementation with a used CIDR from day 4 to 14 after insemination. The maximum temperature humidity index during the study averaged 86, while the minimum was 77. Blood samples were collected from all heifers on days 5, 9, and 14 post-insemination for quantification of progesterone, thyroxine, and triiodothyronine levels. Respiration rate (RR) was measured at 1700 hours and rectal temperature (RT) at 1800 hours, 3 times per week. The conception rate did not differ (P > 0.05) among treatments (C = 40; TAI = 34.6; TAI+S = 44.4%). The levels of progesterone were not increased (P > 0.05) by progesterone supplementation. Values for RR, RT, and thyroid hormones were similar among treatments (P > 0.05). TAI combined with progesterone supplementation did not improve the conception rate of Holstein heifers under heat stress.

Can video cameras replace visual estrus detection in dairy cows?

A 6-mo experiment was conducted in a dairy herd to evaluate a video system for estrus detection. From October 2007 to April 2008, 35 dairy cows of three breeds that ranged in age from 2 to 6 yr were included in the study. Four daylight cameras were set up in two free stalls with straw litter and connected to a computer equipped with specific software to detect movement. This system allowed the continuous observation of the cows as well as video storage. An observation method related to the functionality of the video management software (“Camera-Icons” method) was used to detect the standing mount position and was compared to direct visual observation (direct visual method). Both methods were based on the visualization of standing mount position. A group of profile photos consisting of the full face, left side, right side, and back of each cow was used to identify animals on the videos. Milk progesterone profiles allowed the determination of ovulatory periods (reference method), and a total of 84 ovulatory periods were used. Data obtained by direct visual estrus detection were used as a control. Excluding the first postpartum ovulatory periods, the “Camera-Icons” method allowed the detection of 80% of the ovulatory periods versus 68.6% with the direct visual method (control) (P = 0.07). Consequently, the “Camera-Icons” method gave at least similar results to the direct visual method. When combining the two methods, the detection rate was 88.6%, which was significantly higher than the detection rate allowed by the direct visual method (P < 0.0005). Eight to 32 min (mean 20 min) were used daily to analyze stored images. When compared with the 40 min (four periods of 10 min) dedicated to the direct visual method, we conclude that the video survey system not only saved time but also can replace direct visual estrus detection.

Relationship of ruminal temperature with parturition and estrus of beef cows1

Spring-calving Angus cows (n = 30) were used to evaluate changes in ruminal temperature (RuT) related to parturition and estrus. Cows were synchronized and artificially inseminated with semen from a single sire. Temperature boluses were placed in the rumen at 7.0 ± 0.2 mo of gestation. Boluses were programmed to transmit RuT every 15 min. Cows (BW = 623 ± 44 kg, BCS = 4.9 ± 0.4) calved during 3 wk, and estrus was synchronized at 77 ± 7 d after calving with PGF(2α). Cows were observed every 12 h to detect estrus. Daily average ambient temperatures ranged from 2 to 22 °C during parturition (February to March) and 17 to 25 °C during estrus (May to June). Ruminal temperature from 7 d before to 3 d after parturition and 2 d before to 2 d after visual detection of estrus was analyzed using the MIXED procedure. Ruminal temperatures <37.72 °C were attributed to water consumption and excluded from analyses. Day did not influence (P = 0.36) RuT from d -2 to -7 before parturition (38.94 ± 0.05 °C). Ruminal temperature decreased (P < 0.001) from d -2 to d -1 before parturition (38.88 ± 0.05 to 38.55 ± 0.05 °C, respectively). Ruminal temperature was not influenced (P = 0.23) by day from 1 d before to 3 d after parturition (38.49 ± 0.05 °C). Ruminal temperature at 0 to 8 h after detection of estrus (38.98 ± 0.09 °C) was greater (P < 0.001) compared with RuT at the same daily hour of the day before (38.37 ± 0.11 °C) or the day after estrus (38.30 ± 0.09 °C). Ambient temperature did not influence (P > 0.30) RuT at parturition or estrus. Ruminal temperature decreased the day before parturition and increased at estrus in spring-calving beef cows and has potential use as a predictor of parturition and estrus.

Development and validation of a new method for visual detection of estrus in mithun ( Bos frontalis)

The objectives of this study were (1) to develop a suitable scoring scale for estrus detection based on frequency and reliability of behavioral signs of estrus in mithun ( Bos frontalis) and (2) to validate the accuracy of this method for detection of estrus in primi- and multiparous mithun cows. The study consisted of two experiments. In experiment I, all animals were observed for 30 min at 2 h intervals for at least 35 days, for signs of estrus. Estrus was further confirmed by rectal examination of the reproductive organs and quantification of plasma progesterone concentrations. Based on the frequency and reliability of a particular sign, a cumulative point scale composed of seven estrous signs that were scored with points, ranging from 3 to 100, was developed. When the sum of the scores exceeded 100 points, the animal was considered to be in estrus. This was again confirmed by rectal examination of the genitalia and quantification of plasma progesterone concentrations. Calculation of efficiency and accuracy of the developed scale showed that this scale was 100% efficient and accurate, irrespective of parity. In experiment II, the scoring scale was tested for its efficiency and accuracy for detection of estrus in primi- and multiparous mithun cows based on the behavioral observations recorded twice a day at 0630 and 1630 h for at least 35 days with each observation period lasting for 30 min. Interestingly, efficiency and accuracy of the scale for detection of estrus was 100% in this experiment. Behavioral estrus was more intense in primi- than multiparous mithun cows in both experiments. Duration of estrus was longer in primi- than multiparous animals. The results of the present investigation revealed that no individual behavioral sign of estrus can be used alone for estrus detection in mithuns; whereas the efficiency and accuracy of the scoring scale composed of seven estrous signs were 100%, even when animals were observed twice each day. In conclusion, the scoring scale that has been developed was suitable for detection of estrus in mithuns with high efficiency and accuracy. However, the scale should be validated for use by farmers to assess its practical usefulness.

268 TIMED INSEMINATION OF HEIFERS WITH SEXED SPERM

The objective of this field trial was to compare pregnancy rates in Angus heifers time-inseminated with sexed sperm 55–56 h or 67–68 h after CIDR removal and administration of 25 mg prostaglandin F2α (PGF2α). Timed insemination eliminates labor costs associated with visual detection of estrus. Anecdotally, use of sexed sperm in commercial timed insemination environments has resulted in reduced pregnancy rates compared to rates for visually observed estrus. However, the optimal fixed time of insemination for sexed sperm has not been studied previously. Sperm were stained at 200 � 106 sperm mL–1 with 49 µm Hoechst 33342 for 45 min at 34.5�C and then diluted to 100 � 106 sperm mL–1 for sorting. Sperm were sexed by flow cytometry/cell sorting at 40 psi using a quasi-cw (pulsed; Vanguard 350-HDM, Spectra-Physics, Mountain View, CA, USA) laser operating at 125 mW, resulting in &gt;91% X-chromosome-bearing sperm. Sorted sperm(2 � 106 total) were packaged into 0.25-mL straws at 10 � 106 sperm mL–1 and cryopreserved. Straws contained &gt;43% progressively motile sperm immediately after thawing for 30 s in a 37�C water bath, as determined by 'track' motility. Angus heifers (n = 67) were synchronized for estrus with IM administration of 100 µg gonadotropin-releasing hormone (GnRH) and a CIDR in place for 7 days, followed by 25 mg PGF2α IM. Heifers were inseminated in the uterine body either 55–56 h (the timing currently recommended for unsexed semen) or 67–68 h after CIDR removal, accompanied by 100 µg GnRH IM, balanced across two inseminators with sperm from two Angus bulls. Estrus was visually detected three times daily but not used as the basis for insemination. Two months post-insemination, pregnancywas determined using ultrasound. Datawere subjected to chi-square analysis. Pregnancy rates for heifers inseminated 55–56 h and 67–68 h after CIDR removal were 34% (n = 11/32) and 46% (n = 16/35), respectively (P &gt; 0.1). Estrus was visually detected for 85% (n = 57/67) of the heifers. Four heifers not detected in estrus became pregnant (40%). Respective pregnancy rates resulting from inseminations 0–12 h and 18–24 h after observed onset of estrus were 25% (7/28) and 55% (16/29), respectively (P &lt; 0.05). Based on the limited scope of this preliminary field trial, insemination of heifers with sexed sperm at 67–68 h post-CIDR removal may be preferable to insemination at 55–56 h. It appears to be best to wait 18 to 24 h post-onset of observed estrus to inseminate heifers with sexed sperm when not using fixed-time insemination procedures. A larger field trial is warranted to more accurately identify the optimal fixed time for insemination using sexed sperm.

Technical and economic effects of an inline progesterone indicator in a dairy herd estimated by stochastic simulation

For several years progesterone in milk or blood has been recognized as an indicator of different cow states related to reproduction. For this study, an existing simulation model was modified in order to analyze the technical and economic effects of including information on progesterone status in an automatic inline monitoring system. Implementation of an inline progesterone indicator was assumed to directly affect the estrus detection rate, the period until treatment for post-partum anestrus and the number of mistimed AIs. Different implementations of an inline progesterone indicator were simulated in a typical Danish dairy herd with 120 cows and in other herd situations represented by: a herd with poor reproduction efficiency, a herd with a high estrus detection rate and a herd using a 9 week postponed AI period for primiparous cows. It was concluded that implementation of an inline progesterone indicator in a dairy herd previously using visual estrus detection has a break-even price of €3–81 per cow-year depending on differences in implementation type and herd reproduction management. The highest break-even price was found using the assumptions that simulated a herd with initially poor reproductive efficiency. With the assumptions that simulated a typical Danish herd the break-even price was €46 per cow-year. Attributable effects of using the indicator, including effects of labor time, are discussed.

Effect of the interval between estrus onset and artificial insemination on sex ratio and fertility in cattle: a field study

We have carried out a field trial in cattle to study the effect of the interval between the onset of estrus and AI on sex ratio and fertility. Data were obtained from 716 cows that had been inseminated at different times between 8 and 44 h from the visual detection of estrus. Before analyzing the data, it was grouped in three intervals considering the time between estrus onset and AI (8–18, 18–30, and ≥30 h). Our results show that the percentage of calved females (73.05%) is significantly superior for early inseminations (8–18 h), and it decreases 1.85% per hour from the onset of estrus. Delayed AIs (≥30 h) produce a significant deviation of the sex ratio towards the males (72.06%); nevertheless, fertility (percentage of successful pregnancies) diminishes significantly, from 66.19% (8–18 h) to 45.35% (≥30 h). In conclusion, variations in the interval between the onset of estrus and AI modify sex ratio. However, we must consider its effect on fertility.

Oestrus detection in dairy cows based on serial measurements using univariate and multivariate analysis

Abstract. As visual oestrus detection is difficult to perform in large herds, different technical devices were developed to facilitate oestrus detection. In this investigation the significance of the traits activity, milk yield, milk flow rate and electrical conductivity due to oestrus was analysed. The traits were recorded automatically during each milking on a commercial dairy farm. Oestrus detection was performed for 862 cows on basis of time series consisting of 15 days before oestrus, the day of oestrus and 15 days after oestrus. The day of oestrus was determined by the insemination which caused a calving after 265 to 295 days. The univariate analyses of traits were performed by the time series methods day-to-day comparison, moving average, exponential smoothing and Box-Jenkins three parameter smoothing. For multivariate analyses a fuzzy logic model was developed and modified for the different combinations of traits. The efficiency of the detection models and traits was determined by the parameters sensitivity, specificity and error rate. A moving average was the best suited time series method for oestrus detection by activity data. Sensitivity ranged between 94.2 and 71% and error rate was between 53.2 and 21.5% for threshold values between 40 and 120%. The traits milk yield, milk flow rate and electrical conductivity were not suitable for univariate oestrus detection. Depending on the considered traits multivariate analyses resulted in sensitivities between 87.0 and 87.9%. The error rate varied between 28.2 and 31.0%. Further analyses should include previous information such as time since last oestrus.

Relationship among estradiol, cortisol and intensity of estrous behavior in dairy cattle

Economic profitability of a dairy farm is based, in part, on the calving interval of the cows. The optimal interval is 365 d. To achieve this, the cow needs to be pregnant within 85 d post partum. The first and most problematic step in this process is the determination of the optimal time for insemination, which is based on estrous behavior. The expression of estrous behavior, however, is at a low level in modern dairy herds, resulting in low detection rates and longer calving intervals. In the present study, a point scale was used to monitor postpartum, nonpregnant cows for estrous symptoms. Frequent blood samples were taken around estrus, and the cows were fit with pedometers to measure their activity. Correlations between the occurrence of symptoms of estrus and levels of estradiol and cortisol were then analyzed. Standing heat, the standard symptom of estrus, was observed in only 53% of the cows. A high correlation of 0.7 was found between estradiol concentration and estrous behavior. This was empasized by the fact that the estradiol level reached its highest level of 7.76 + 2.39 (SD) pg/mL at the same time as the highest behavior score. The highest pedometer readout lagged 8 h behind this moment. Cortisol levels did not exceed the physiological levels in rest situations but showed an increase at the time estrous behavior was at its maximum. The present study showed that standing heat is not the primary symptom for detecting estrus in cows. Pedometers are a useful aid but they have to be read several times a day. The high correlation between the visual symptoms of estrus and estradiol concentrations indicates that visual estrus detection is an efficient, reliable way to determine the right time for insemination

Ovarian and Estrous Response of Suckled Beef Cows to the Select Synch Estrous Synchronization Protocol11This research was supported by a grant from Select Sires. The authors express their appreciation to Select Sires and to Merial, Pharmacia &amp; Upjohn, and DDx, Inc. for their generous donations of Cystorelin, Lutalyse, and HeatWatch, respectively, and to Dave Schutz and Doug Couch at the

Abstract This study evaluated ovarian and estrous responses as affected by day of the estrous cycle at initiation of treatment among cows synchronized with the Select Synch protocol. Fifty-six suckled Hereford x Red Angus multiparous cows were fitted with HeatWatch® electronic estrous detection monitors 22 d before initiation of treatment. Thirty-two percent of cows were not detected in estrus during this 22-d period, and were classified as anestrus. Treatment included an injection of Gonadotropin releasing hormone (GnRH; 100 μg) on d 7, followed by an injection of Prostaglandin F 2 α (PGF 2 α ; 25 mg) on d 0. Ovaries of cows were scanned daily via ultrasound from d 12 until the time of insemination to evaluate follicular and luteal response to the GnRH and PGF 2 α injections. Cows were visually observed for signs of estrus twice daily from d 0 to d 5 for approximately 2 h to compare visual detection of estrus with electronic detection. There was no difference (P>0.5) in the percentage of cows detected in estrus between visual (85%) and electronic (88%) observation. Ovarian and estrous responses to the GnRH and PGF 2 α injections were dependent on day of the estrous cycle when the protocol was initiated. Ovulation resulting in formation of a new corpus luteum (CL) and follicular turnover occurred following the injection of GnRH in 66 and 70% of cows, respectively. Only 14% of cows that were between d 15 and 17 of their estrous cycle responded to either GnRH or PGF 2 α administration. Additionally, these cows exhibited estrus 11 ± 19 h (mean ± SD) before injection of PGF 2 α . Anestrous cows exhibited estrus earlier (P 2 α injection is important.

Validation of a new method of visual oestrus detection on the farm

Summary Since visual observation is the most commonly used way of detecting oestrus and is supposed to be as effective as detection with technical devices, we evaluated a recently developed oestrus detection scoring system in daily dairy practice. In this scoring system nine signs of oestrus are scored with points, ranging 3 to 100. Twenty‐one dairy farmers used the scoring system during a period of 3 weeks. All cows that were more than 30 days post partum and not confirmed pregnant were monitored, using the scoring system, by the herd owners. Oestrus was confirmed by measuring progesterone concentrations in milk. With the scoring system a detection rate of 47% was achieved. This was lower than expected, because in an earlier control period, the detection rate was 64%. We concluded that this new method might be too complicated to introduce to normal herd management, because in daily practice it is too demanding to watch cows twice a day for 30 minutes, especially if the cows show only vague and infrequent symptoms of oestrus. It also appeared to be too complicated to watch the herd at the most appropriate time. However, if the scoring system is included in the daily routine, meaning that farmers are trained to watch for other symptoms than standing heat only and are able to recognize their different values, it can be a valuable aid to oestrus detection.

A note on silent ovulation identified by using radiotelemetry for estrous detection

This study was undertaken to determine the occurrence of silent ovulation (SO) in high-producing, postpartum (PP) Holstein cows. Nineteen high-producing, multiparous cows received transmitters (Heatwatch®, DDX, Denver, CO) for radiotelemetry (RT) and began visual estrus detection (VED) routine for 1/2 h twice daily, on day 10 PP. Blood samples were obtained every other day commencing on day 10 PP, for RIA of progesterone (P 4). Following P 4 assay, RT and VED data were evaluated at time periods coinciding with ovulation to determine whether standing estrus had occurred. First ovulation occurred at 29.1±3.0 days PP (range 17–69 days) compared 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 second PP ovulations ( n=16), VED indicated 50% SO while the inclusion of RT indicated only 12.5% true SO. During third and fourth PP ovulations ( n=15), VED indicated 33.3% SO while the inclusion of RT indicated only 6.7% true SO. When RT was associated with ovulation, there were fewer mounts at first PP ovulations compared to subsequent ovulations (1.1±0.1 vs. 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.

Reproductive traits of Angus, Criollo and reciprocal crossbred females in the temperate area of Argentina

AbstractReproductive performance of purebred Angus (A) and Criollo (C) cows and crossbred CA and AC cows in the temperate area of Buenos Aires, Argentina, was assessed through the study of reproductive rates, calving date, first insemination date, number of inseminations and weight related variables. The herd was grazed on pastures all year round. Matings were by artificial insemination with visual oestrus detection, from October to December. Heifers first calving was at 3 years of age. All traits were analysed with general linear models including, as corresponded, fixed effects of dam and calf genetic groups, calving year and month, dam physiological status, calving age and first order interactions. Female genetic group adjusted means were used to estimate direct (gl) and maternal (gM) breed differences and heterosis (hl) effects on reproductive traits. Weaning rate was mostly determined by oestrons detection rate. Due to the inhibitory effects of nursing on reproduction, female genetic group effects were significant for suckling cows only: mean oestrous detection rate was higher (P &lt; 0·05) for crossbred cows (AC: 91·2 (s.e. 5-1) %; CA: 88·4 (s.e. 2·9) %) than for A (76·3 (s.e. 2·0) %) and C (49·9 (s.e. 3·3) %); direct breed effects favoured A (glA - g1c = 26·4 (s.e. 3·7) %; P &lt; 0·001) and h1 was 26·7 (s.e. 3·4) % (P &lt; 0·001). When only oestrous-detected cows were considered, direct breed effects were significant only for pregnancy rate fg1A —g1c = 8·5 (s.e. 4·4) %) whereas h1 was significant for pregnancy (8·3 (s.e. 3·8) %), calving (9·3 (s.e. 4·1) %) and weaning (10·1 (s.e. 4·1) %) rates (P &lt; 0·05). Criollo cows calved later than crossbred (≍19 days) and A (≍15 days) cows mainly due to longer post-partum anoestrous. For calving date, direct breed effects favoured A (g1A — g1c = 20·8 (s.e. 5·9) days; P &lt;0·0·001) and h1 was 11·4 (s.e. 2·8) days (P &lt; 0·001). Low reproductive performance in C was not associated with live iveight at the beginning of mating. This genetic group was the latest in showing oestrous behaviour, even when not suckling. Number of inseminations was similar for the four genetic groups. These results sustain the principle of utilizing Fl Criollo-Angus cows to improve beef herd productivity, whereas they do not support the recommendation of using purebred Criollo females under this type of production system.

Relationships between observable oestrous behaviour and the number of heifers in oestrus

The accurate detection of oestrus in beef and dairy cows prior to AI or embryo transfer (ET) is essential if optimal pregnancy rates are to be acheived. In dairy cows under normal husbandry conditions only 55% of normally cycling animals are correctly detected in oestrus and inseminated at the appropriate time (Esslemont and Bryant 1976). The use of pedometers, changes in milk yield, milk progesterone and trained sniffer dogs are all methods which can significantly improve the oestrus detection and hence pregnancy rates acheived by AI (Phillips and Schofield, 1988: McLeod, Foulkes, Williams and Weller, 1991; Jezierski, 1988) . However, oestrus detection by visual monitoring is still the most widely used method of detection.To ensure high pregnancy rates from AI or ET when visual oestrus detection methods are used the form and range of behaviours which cattle perform needs to be understood. There are a wide range of oestrus behaviour patterns displayed both within and between individual cows so deciding on the correct time for AI or ET depends on interpreting the available evidence. This paper reports the behaviour of maiden heifers during natural oestrus and following a pharmacologically induced oestrus (designed to synchronise the time of oestrus for a number of heifers). By understanding the range of oestrus behaviour patterns guidelines can be established for observation methods and the interpretation of oestrus behaviour. This should enable the prediction of the optimum times for AI or ET. A corresponding improvement in the number of pregnancies should be acheived.

Confirmation of Estrus Rates by Palpation per Rectum of Genital Organs in Normal Repeat Dairy Cows

Data were from 6084 normal repeat to second service cows, visually detected in estrus, in a commercial artificial insemination program on a.m./p.m. schedule. The percentage of cows confirmed in estrus by rectal examination and inseminated after palpation was 96.2. The remainder of the cows were not inseminated and non-return rate for these cows was 86.9% (150-day non-return). In cows confirmed in estrus, the percentage of cows ready for service at palpation was 96.1 and the 150-day non-return percentage for these cows (43.9) was different from those cows in which estrus and insemination were considered incorrectly timed (26.7%). These results suggest that the efficiency of reproduction in dairy herds may be improved by examination per rectum of the genital organs at insemination as an effective complement to visual detection of estrus.

Accuracy of predicting the LH surge and optimal insemination time in Holstein heifers using a vaginal resistance probe

Monitoring changes in vaginal electrical resistance in association with ovarian follicular development during proestrus may provide an alternative to visual estrus detection of cattle for properly timing insemination. In two experiments 94 Holstein heifers were synchronized into estrus with 2 injections of prostaglandin F 2 alpha (PG) 11 d apart. Beginning 12 h prior to the second PG treatment, blood samples and vaginal resistance measurements were taken every 12 h for 60 h, and then every 6 h for the following 48 h. In both Experiments I and II, the lowest resistance value was found to be highly correlated with the luteinizing hormone (LH) preovulatory surge (r = 0.67 P<0.001). The linear regression of time from PG to the LH surge (Y) on time from PG to the lowest resistance value (x) was defined by Y = 17.49 + 0.71 (x) (R 2 = 0.45). This suggests that the lowest resistance value can predict the LH surge and, therefore, the appropriate time to inseminate heifers relative to the expected time of ovulation. This concept was tested in Experiment II by assigning 50 heifers to be inseminated after PG treatment on the basis of their vaginal resistance pattern, by appointment 66 h after PG, or by visual observation of standing estrus. Conception rates were 58, 50 and 50% in these groups respectively, and did not differ significantly. Overall, these results suggest that measurement of vaginal resistance patterns reliably predict the LH surge and can be successfully utilized to inseminate cattle.

Estrus Detection and Estrus Detection Aids

There is no substitute for good management. Each animal should be identified carefully. The herdsman should know all signs of estrus or impending estrus. In addition, for visual detection of estrus to be highly effective, sufficient time must be taken at least twice a day to catch animals with a short estrus period. Presently there are two visual aids to estrus detection which provide potential 24-h surveillance. One aid is a pressure sensitive device mounted on the back of each cow which can be triggered when the cow stands for mounting. The second one is a marking device worn by sexually aggressive animals which will stripe with colored ink the back of estrous animals as the marker animal mounts and dismounts. Both devices are effective when used properly. Other tests of changes in cervical mucus, vaginal characteristics, temperature, blood flow, and hormone changes in blood and milk are either not sufficiently reliable or else simple enough yet to be practical aids for routine detection of estrus in dairy cattle. Milk progesterone can assist in characterizing problem cows