Anestrus and Estrous Detection Aids IRM-7 Dairy Integrated Reproductive Management Dr. M.A. Varner University of Maryland The accurate and efficient detection of estrus (heat) in dairy cattle is an important component of a good reproductive management program. Failure to observe cows in estrus is the biggest cause of reproductive management problems in most herds. Individual cows may not be observed in estrus for one of two reasons. First, the ovaries of the cow are not functioning properly and the cow is anestrus (failure to have an estrous cycle). The second reason is that the dairy producer misses seeing a cow that actually is in estrus. While the second reason is the most common in herds, it is not uncommon for a particular producer to have both problems in a herd. The extent of these problems varies greatly among herds. The percentage of cows in a herd without a normal estrous cycle by 60 days can range from less than 5% to over 20%. The percentage of missed estrous periods can range from less than 15% to over 60%. Anestrus or missed estrous periods can reduce profits significantly (Fact Sheet IRM-17). It is important that dairy producers who are having problems detecting cows in estrus determine which of the two causes of the problem is most important for their herd. Steps can then be taken to effectively correct the problem(s). This fact sheet describes a method of determining whether anestrus or missed estrus is the major problem in estrous detection for a herd. It also discusses methods for correcting the problem(s). Determining the Problem Records of a veterinarian s palpation of the cow s ovaries, palpated at least monthly, and all dates of first observed estrus are necessary to determine whether anestrus or missed estrus is the cause of failure to detect cows in estrus. If a producer does not have these records available, collection of this information is the first step in determining the problem. It takes 6-9 months to accumulate sufficient records to make meaningful comparisons. Records from two-thirds of the total number of cows in the herd need to be summarized. In general, if only a minor problem with anestrus exists then the cause of estrous detection problems is due to the dairy producer not efficiently detecting cows in estrus. If anestrus is a problem, there also may be problems with missed estrous periods. Again, only careful examination of records can determine if one or both problems exist in a herd. Anestrus Summarize records as follows: 1. Exclude cows diagnosed with cystic ovaries. If over 15% of the herd is diagnosed as cystic, refer to the Fact Sheet IRM-25 for suggestions on correcting the problem. 2. Examine each cow s palpation records for the first 90 days postpartum (after calving). List the number of days postpartum when each palpation occurred and what ovarian activity (presence of a CL or follicle) was palpated. 3. If palpations are conducted monthly, calculate the percentage of cows palpated prior to 60 days postpartum that do not have at least one palpation with ovarian activity. Herds having more than 10% of the cows with no ovarian activity by 60 days postpartum have a problem with anestrus.
4. 5. When palpations are conducted twice monthly, calculate the percentage of cows palpated prior to days 35 and 45 postpartum that do not have at least one palpation with ovarian activity. Herds that have more than 35% of the cows with no ovarian activity by 35 days postpartum and more than 5% of cows with no ovarian activity by 45 days postpartum have a problem with anestrus. If palpations are conducted more than twice monthly, calculate the percentage of cows palpated prior to days 24, 32, and 40 postpartum that do not have at least one palpation with ovarian activity. Based upon research results in Table 1, normal herds have at least 50% of the cows with ovarian activity by day 24, more than 70% of cows by day 32, and over 95% of cows by day 40 postpartum. Missed Estrus Summarize records as follows: 1. Exclude cows diagnosed with cystic ovaries as discussed previously. 2. Calculate the number of days from calving until first observed estrus for each cow. 3. Determine the average days until first estrus and the percentage of cows that have been observed in estrus before days 50 and 63 postpartum. Over 70% of cows should be observed in estrus by 50 days postpartum, and over 95% of cows by 63 days, based upon the research data in Table 1. If the average days to first estrus for a particular herd exceeds 38 days, but the 50 and 63 day percentages do not exceed the values in Table 1, then the missed estrus problem is due only to a few cows. If days to first estrus exceed the 50 and 63 day percentages, then missed estrus is a problem in the entire herd. The estrous cycle associated with the resumption of ovarian activity after calving usually has a silent estrus or does not have a period of standing estrus. This early silent estrus is the reason for the difference in days to ovarian activity and first estrus in Table 1. Research indicates that in normal cows silent estrus seldom, if ever, occurs after the first postpartum estrus. What To Do Anestrus Inadequate nutrition (Fact Sheet IRM-14) and uterine infections (Fact Sheet IRM-22) are two important causes of anestrus in cows. The feeding program in herds with estrous detection problems due to anestrus should be examined carefully to ensure that adequate levels of nutrients, especially energy, are being provided. Management procedures regarding dystocia or problem calvings (Fact Sheet IRM-20) and retained placentas (Fact Sheet IRM-21) should also be carefully examined for herds with problems due to anestrus. Dystocia and retained placentas often lead to uterine infections, which can delay the beginning of ovarian activity and subsequent estrus. Missed Estrus All herd personnel responsible for estrous detection in herds that have problems with missed estrus should review and/or become familiar with the various behavioral and physical signs of estrus (Fact Sheet IRM-6). In addition, the overall management program for estrous detection should be reviewed and evaluated. Six steps have been recommended (Fact Sheet IRM-6) to evaluate a herd s estrous detection program. Estrous detection aids, other than a heat expectancy chart, should not be used until all herd personnel fully understand the signs of estrus and the estrous detection program has been evaluated. Table 1. Average Days Postpartum When Two Types of Activity First Occur in Normal Cows. Days Postpartum 1 Type of When 70% of Cows When 95% of Cows Average For Activity Have Activity Have Activity All Cows Ovarian Activity 2 32 days 40 days 24 days First Estrous Activity 3 50 days 63 days 38 days 1 Days postpartum for percentages were determined from mean and standard deviation. 2 Days to first postpartum ovulation. 3 Days to first observed estrus. Table adapted from Britt, J. H., et al., 1974. J. Anim. Sci., 39:915-919. 2
Estrous Detection Aids Estrous detection aids used in dairy herds are heat expectancy charts, pressure-sensitive mount detectors, tail chalk, detector animals, and electronic aids. They may be used to help identify cows that are in estrus but may otherwise go unnoticed. There are two important conclusions from research conducted using many of the estrous detection aids. First, breedings based solely on estrous detection aid indicators are not as fertile as breedings in the same herd based upon observed standing estrus. Estrous detection aids sometimes inaccurately indicate cows as being in estrus when they really are not. Consequently, standing estrus should be used as the primary sign for timing of artificial insemination. Estrous detection aids should be used to identify cows requiring extra observation for standing estrus. An example is using a record of restlessness and clear watery mucus from the reproductive tract of a particular cow recorded on a heat expectancy chart 19 days ago. This cow is then identified for close observation over the next few days. Fertility of breedings based on information from one estrous aid and confirmed by another aid may be acceptable in some herds. For example a cow that had clear watery mucus 21 days ago and has an activated pressure sensitive mount detector today. Second, research indicates estrous detection problems and breeding fertility sometimes get worse when an aid is used on the entire herd. This problem may be the result of herd personnel not watching the cows for standing estrus as intensively when they have an estrous detection aid to use as a crutch to fall back on. Thus it is recommended that estrous detection aids be used only on cows that are difficult to detect in estrus. Heat Expectancy Chart Heat expectancy charts are special calendars used to record information. They are probably the least expensive and most valuable estrous detection aid available. The types of information recorded on the chart include signs of estrus and results from using other estrous detection aids. Information recorded on a heat expectancy chart also may be useful to a veterinarian diagnosing a cow that is a problem breeder. Heat expectancy charts are often available at low cost through artificial insemination organizations. Pressure-Sensitive Mount Detectors Pressure-sensitive mount detectors are probably the most commonly used estrous detection aid, other than a heat expectancy chart. One type of commercially available mount detector is pictured in Fig. 1. Mount detectors are glued to the rump of a cow according to the directions supplied by the manufacturer. The mount detector is activated by the weight of another cow mounting the cow on which the mount detector is attached. Activation changes the detector s color. Partially triggered detectors may indicate a cow is coming into estrus. Helpful hints for use of mount detectors include: 1) write the cow s identification number on the tag in case the detector is rubbed off during mounting, 2) remove all objects such as back scratchers or low branches that may falsely trigger the mount detector, 3) do not apply the detectors to wet animals and 4) use ample quantities of application cement. The biggest problem with pressure-sensitive mount detectors is false triggering. As a consequence, cows are bred when they are not in estrus which results in low conception rates for the herd. If the cow was bred previously, an abortion may result from breeding the cow when she was not actually in estrus. Use of other signs of estrus or other estrous detection aids to confirm a triggered mount detector is essential to obtain acceptable conception rates. Tail Chalk, Crayon, or Paint These types of estrous detection aids are most commonly used in large herds. A cow that has been mounted has the chalk or paint rubbed off or smudged. Little research has been done to determine the best use of chalk or tail painting. Chalk or paint appears to be nearly as effective as pressure-sensitive mount detectors, while being less expensive. The disadvantages are: 1) cows may need to be rechalked as often as every 2-4 days, 2) chalking may require restraint of the animal and 3) false chalk smearing may occur. False chalk smearing may be due to rubbing on low branches, back scratchers, or free stalls. It is important that results from tail chalk be confirmed by other signs of estrus or other estrous detection aids to obtain acceptable conception rates. 3
Fig. 1. A commercially available pressure-sensitive mount detector and its applicator. Fig. 2. Use of a commercially available device that measures the electrical resistance of secretions in the vagina. Detector Animals Two types of detector animals are commonly used: surgically altered bulls and hormone treated animals. Vasectomized bulls are altered surgically so that normal mating may occur, but sperm transport is blocked. Gomer bulls are altered surgically to prevent contact between the penis and the cow. Most commonly, the pathway of the penis is altered so that it exits to the side of the bull so he cannot service a cow. A commercially available device (Pen-O-Block), consisting of a plastic tube that is attached to the sheath of the bull and blocks contact with the female, has also been used. Complications with this device, such as infections in the bull, however, may result. The advantages of using an altered bull as a detector animal are that most cows in estrus will be mounted by a bull. Also a more intense estrus may be displayed by cows exposed to a bull. Research results have shown no more than 30-40 open cycling cows should be grouped per bull for efficient detection of estrus. Consequently, herds that have similar numbers of cows calving each month of the year may need only one bull per 100 cows. The disadvantages of having a surgically altered bull in the herd include: 1) danger of an aggressive bull, 2) feed costs of maintaining a bull, 3) transmission of venereal diseases by a vasectomized bull, 4) cost of surgical alteration by a veterinarian, and 5) a decrease in libido or sex drive by some gomer bulls. The decrease in libido in gomer bulls results in poor estrous detection efficiency. Cows, freemartin heifers, or steers that are treated with the reproductive hormones testosterone or testosterone and estrogen, also may be used effectively as estrous detector animals. However, field observations suggest that only 75% of injected animals will respond to treatment. The main advantage of using a hormone treated animal is that nearly all cows in estrus will be mounted. It is not known if estrus is more intense for cows exposed to a hormone-treated animal. Stocking rates for hormone-treated animals are similar to those for bulls. 4
The disadvantages of hormone treated animals are: 1) danger of an aggressive animal, though the danger is probably less than with a bull, 2) animals must be injected every 2-4 weeks, 3) costs of maintaining the animal and of injections, 4) not every animal responds to the hormone treatment, 5) lactating cows may not be injected if the milk is to be used and 6) a withdrawal period for hormone injections is required before slaughter. Estrous detector animals (bulls and hormone treated animals) are sometimes fitted with a chinball marking device which leaves a colored fluid on any cow that is mounted. The advantage of a chin-ball marker is that cows in estrus need not be observed standing. This may be especially important for animals on pasture. Disadvantages include: 1) frequent refilling of the colored fluid in the marking device may be required, 2) unnoticed damage to the device and leakage of the fluid may lead to unmarked but mounted cows and 3) preference towards one cow in estrus may be shown by the detector animal. This can cause unfavored cows to not be marked adequately. Electronic Aids Two types of electronic estrous detection aids have recently become available, and others will be available in the future. The devices currently being used measure either a change in electrical resistance of vaginal secretions or an increase in physical activity of cows in estrus. A commercially available device that measures changes in electrical resistance of vaginal secretions is pictured in Fig. 2. The advantages of this device are: 1) it may be used to indicate when a cow may be coming into estrus, indicating that intensive observation is needed and 2) the device can be used to identify cows that have problems with their reproductive tract. The disadvantages are: 1) cost of the device, 2) cows should be evaluated with the machine daily to predict time of increased observations and 3) the portion of the device that is placed in the cow should be sterilized between cows to insure that disease is not spread. Extensive scrubbing of the probe with a disinfectant followed by a clean water rinse and drying with a single-use paper towel may provide some protection against the spread of disease between cows. Electronic pedometers are devices that record the amount of walking done by a cow. Devices currently available have a miniaturized computer in each pedometer that measures the amount of change in walking activity between days. The amount of change is used to tell when a cow is in estrus. Results with these devices indicate that breedings based solely on pedometer readings are of comparable fertility to breedings based on time of standing estrus. How long the devices will last and whether the devices will pay for themselves are questions that remain to be answered. References Britt, J.H., R.J. Kittok, and H.S. Harrison. 1974. Ovulation, estrus, and endocrine response after GnRH in early postpartum. J. Anim. Sci. 39:915-919. Foote, R.H. 1975. Estrus detection and estrus detection aids. J. Dairy Sci. 58:248. Kiddy, C.A. 1979. Animal Reproduction (Beltsville Agricultural Research Symposium Number 3). H. Hawk, ed. Allanheld and Osmun PubI., Montclair, NJ. Kiser, T.E., J.H. Britt, and H.D. Ritchie. 1977. Testosterone treatment of cows for use in detection of estrus. J. Anim. Sci. 44:1030-1035. Stevenson, J.S., and J.H. Britt. 1977. Detection of estrus by three methods. J. Dairy Sci. 66:1994-1998. Williams, W.F., D.R. Yver, and T.S. Gross. 1981. Comparison of estrus detection techniques in dairy heifers. J. Dairy Sci. 44:1738-1741. Trade or brand names are mentioned only for information. The Cooperative Extension Service intends no endorsement nor implies discrimination to the exclusion of other products which also may be suitable. Programs and activities offered by the West Virginia University Extension Service are available to all persons without regard to race, color, disability, religion, age, veteran status, sexual orientation or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Director, Cooperative Extension Service, West Virginia University. 5