How Long Does A Dairy Cow Usually Stay In Service?

Efficient and profitable reproductive performance of a dairy herd requires routine but conscientious heat detection and proper timing of artificial insemination. Failure to observe estrus (heat) is a major factor contributing to low fertility. Approximately half of the heats are undetected on dairy farms in the United States. In add-on, research based on levels of the hormone progesterone in milk shows that up to 15 per centum of the cattle presented for insemination are not in rut. Failure to discover cows that are in heat and breeding cows non in heat event in economical loss for the producer because of extended calving intervals and additional semen expense. If a herd producing xvi,000 pounds of milk per twelvemonth and maintaining a 12.5 month calving interval is compared with the same herd maintaining a 13.5 month calving interval, the loss in potential milk alone is between $35 and $45 per cow per year, depending on milk price and feed costs. Therefore, poor heat detection is plush to the producer and should be considered the critical component of reproductive management.

Efficient heat detection and timely insemination also are important to beef producers who apply artificial insemination. Failure to find oestrus early on in the breeding flavour or improper timing of insemination due to heat detection errors results in extended calving intervals and additional semen expense.

This publication provides information on characteristics of the estrous cycle, signs of oestrus and estrous behavior, factors affecting expression of estrus, and management suggestions for improving heat detection. Various means to monitor the efficiency of heat detection and several oestrus detection aids also are described.

Characteristics of the Estrous Wheel

In general, there are two structures that can be constitute on the ovary, the corpus luteum and follicles of various sizes. Information technology was thought that several follicles developed big fluid cavities (antrum) toward the end of the cycle or prior to the first postpartum heat simply that only one or two follicles were ascendant and ovulated, releasing the oocyte (egg) shortly after heat. The other follicles were thought to degenerate and a corpus luteum to develop at the site of ovulation. Recent studies, however, reveal unlike changes in growth and degeneration of follicles during the cycle.

Using existent-time ultrasound technology to monitor ovarian structures on a daily footing, several contained inquiry groups have shown that cows or heifers may have two, three, or four groups of follicles that develop during each estrous wheel. Usually, a single follicle within each group becomes dominant, suppressing the continued growth of the other follicles within that group. Such groups of developing follicles are called "waves" of follicular growth. Thus various populations of small, medium, and big follicles are nowadays on the ovary each day of the bike.

On well-nigh solar day 18 of a normal 21-mean solar day cycle, the corpus luteum (CL) that developed later the previous ovulation begins to regress and progesterone concentrations decline. The dominant follicle of this last moving ridge continues to increase in size and produces the hormone estrogen. Since progesterone concentrations are depression, estrogen causes the characteristic signs and behavior associated with heat. At the beginning of continuing rut, estrogen also initiates the release of a surge of luteinizing hormone (LH) from the anterior pituitary gland in the brain.

Luteinizing hormone begins the process of ovulation, which occurs approximately 25 to 32 hours afterward the onset of continuing heat. At the site of ovulation, the new CL increases in size and gradually produces increasing amounts of progesterone. Concentrations of progesterone in the blood remain high from well-nigh 24-hour interval 6 through day 18 of the bike. Although follicles keep to develop and even produce estrogen (estrogen-active follicles) during midcycle, the loftier level of progesterone prevents their final maturation and inhibits expression of heat. Eventually these larger follicles degenerate and estrogen production declines.

Progesterone too prepares the uterus for pregnancy, inhibits uterine contractions, and maintains pregnancy. The CL regresses in cows that fail to become pregnant and progesterone levels reject, the ascendant follicle completes evolution, and the cow returns to heat, initiating a new cycle. If pregnancy occurs, the CL does not regress and progesterone levels remain elevated throughout pregnancy.

Thus the estrous wheel can be divided into four periods: proestrus, rut, metestrus, and diestrus. Proestrus is the period when progesterone declines with regression of the CL, estrogen increases, and secondary signs of estrus brainstorm to occur. Estrus is characterized by standing behavior (truthful heat). Metestrus begins immediately after heat when ovulation and early on development of the CL occur, a menses that lasts three to five days. Finally, diestrus is the time when the CL is functional, the longest phase of the estrous bike.

Figure ane illustrates the structural changes on the ovaries and the hormone concentrations during an estrous wheel with three waves of follicular development. Although specific days of the cycle are indicated on the diagram, this is for illustration purposes but since at that place is variation amongst cows.

Figure 1. Changes in ovarian structures and hormone concentrations during the estrous cycle. For simplicity, only one ovary is illustrated; however, structural changes are occurring on both ovaries. Specific days of the bike are listed for analogy but. There is variation among cows.

Signs of Estrus

Standing and mounting activity.

Chief sign

A moo-cow standing to be mounted is the well-nigh authentic sign of estrus. Standing heat is the most sexually intensive menstruation of the estrous bicycle. During this catamenia, cows stand to be mounted by other cows or move forrad slightly with the weight of the mounting cow. Cows that motility away quickly when a mount is attempted are not in true estrus. In gild for continuing behavior to be expressed, cattle obviously must exist allowed to interact.

The expression of oestrus is due to the elevated level of estrogen in the claret when progesterone is very depression. Occasionally cows in early pregnancy, budgeted the end of pregnancy, or with ovarian follicular cysts have similar hormonal relationships and may express signs of estrus.

The average elapsing of standing heat is xv to 18 hours, but estrus duration may vary from 8 to 30 hours among cows. An estrous cow usually stands to be mounted 20 to 55 times during her estrous flow. Each mount lasts three to vii seconds. Factors that touch on expression of rut are discussed in a later section.

Secondary signs

Secondary signs vary in duration and intensity. These signs may occur before, during, or later standing heat and are not related to fourth dimension of ovulation. Dairy producers should use these signs as clues or watch the specific cow more than closely for continuing behavior. To determine whether cows exhibiting secondary signs will stand to exist mounted, they may be isolated with a sexually active cow or teaser creature.

Mounting Other Cows

Cattle that exhibit this beliefs may be in estrus or approaching heat. Mounting action is performed much less oft by cows in midcycle. Although mounting cannot be used as a true primary sign of heat, cows exhibiting such behavior should exist watched closely for continuing behavior.

Mucus Belch

As an indirect result of elevated estrogen levels, mucus is produced in the cervix and accumulates with other fluids in the vagina before, during, and soon after estrus. Long pasty, clear rubberband strands of mucus more often than not hang from the vulva. Sometimes, however, the fungus does not appear externally until the cow is palpated during insemination and the mucus is expelled. Fungus also may be smeared on the tail, thighs, flanks, or perineal region.

String of clear mucus being discharged.

Swelling and Reddening of the Vulva

During heat the vulva swells and the interior becomes moist and carmine. Generally these symptoms appear before oestrus and remain for a short menstruum afterward heat. Thus they are not precise indicators of estrus. During midcycle the lips of the vulva are pale and more difficult to split up.

Bellowing, Restlessness, and Trailing

Cows in rut are more than restless and alert to their surround. When immune to interact with other cattle, cows coming into heat "proestrus" and cows in rut persistently trail behind to effort to mount other cows. Research shows that cows in rut spend less fourth dimension resting than nonestrous herdmates. Prior to and during estrus, they remain standing and alert while their herdmates are lying downwards and resting. This is more noticeable for stanchioned cows. Cattle may bellow more frequently during estrus. Although these are not definitive signs of heat, cows exhibiting such beliefs should be watched closely for continuing behavior.

Rubbed Tailhead Hair and Muddy Flanks

Equally a effect of beingness ridden, the hair on the tailhead and rump is fluffed-up, rubbed, or disordered, and the skin may be exposed. The legs and flanks may be smeared with mud or manure.

Chin Resting and Back Rubbing

Prior to mounting, cows often rest or rub their chin on the rump or back of the cow to be mounted. This application of pressure may be considered a test for receptivity to being mounted. Both cows should be observed closely for mounting and standing behavior.

Chin resting and trailing activity.

Sniffing Genitalia

Sniffing the ballocks and licking the vulva of other cows occur much more frequently with cows in proestrus and estrus.

Head Raising and Lip Curling

Mostly this activity follows sniffing of the genitalia and occurs more than oft if the cow being investigated is in oestrus and urinates.

Decreased Feed Intake and Milk Yield

Estrous cows spend less fourth dimension feeding. Some studies also accept reported decreased milk yield during estrus, and a Canadian study reported a slight increase in milk yield toward the end of heat. But since many factors other than estrus can affect milk yield on a specific day, this is not a reliable indicator of estrus.

Metestrous Bleeding

Some cows and nigh heifers take a bloody mucus belch one to three days afterward rut, but onset of this symptom, called metestrous bleeding, is quite variable. High estrogen levels during estrus cause blood to leak from vessels almost the surface of the uterus. This belch indicates that the cow was in heat and does not mean that she failed to conceive. However, such animals should be watched closely for a return to heat in 18 or 19 days.

Factors Affecting Estrous Behavior

Arrangement where cattle are crowded.

Type of Housing

Any housing arrangement that allows cattle to interact throughout the day provides more opportunity for mounting and standing behavior to be expressed. Cattle housed in necktie-stall or stanchion barns must exist turned out in order for this behavior to be expressed. If cattle are not allowed to collaborate, the herd manager must use less reliable secondary signs to determine which cows are in heat. Caution: It would be incorrect to assume that more heats are observed in loose-housing or costless-stall barns than in necktie-stall or stanchion barns. Although there is a greater opportunity to observe heat when cows interact frequently in free-stall barns, taking time to observe estrous behavior is still necessary.

Footing Surface

To what extent does a slippery footing surface touch expression of estrus? Research conducted in North Carolina compared estrous activity of high-producing Holstein cows that were watched for heat for one hour every viii hours, 30 minutes on dirt and xxx minutes on grooved physical. Table one shows total mounts and stands during estrus and boilerplate number of mounts and stands during a 30-minute oestrus check period. Duration of heat was longer for cows observed on dirt. Mounting and standing behavior were nearly doubled when cows were checked for rut on dirt every bit compared to concrete.

Table 1. Mounting and standing activity of thirteen Holstein cows on dirt and concrete.
Action	Dirt	Concrete
Source: J. Britt et al. (1986), Journal of Dairy Science 69: 2195.
Elapsing of heat (hours)	13.8	nine.four
Total during estrus
Mounts	seven.0	3.2
Stands	6.3	2.9
Average during xxx-minute estrus check
Mounts	3.7	ii.5
Stands	3.8	2.seven

A second study also confirmed that mounting activity occurs more often when cows are on dirt rather than concrete. When five estrous cows were individually presented with an opportunity to spend time on dirt or on concrete in the presence of a tied moo-cow which was either an estrous moo-cow or a cow not in estrus, the examination moo-cow spent an average 70 percent of the fourth dimension on dirt. The test estrous cow mounted more frequently when a tied estrous cow was on dirt rather than on physical.

Finally, in a Purdue University study in which heifers were housed in a free-stall barn with admission to a bedded pack and observed continuously for estrous behavior over a 96-hour period, 70 percent of the mounting activity occurred in the bedded pack area. Less activeness was observed in the dry out lot, in the costless-stall area, and near the feed bunk (Table ii).

Table two. Percentage of mounting and standing to exist mounted behavior in various locations in a loose-housing system.
Location	Mounts and standing behavior
Location	Number	% of total
Source: J. Pennington et al. (1985), Agri Exercise, Vol. 6, No. 9.
Bedded pack	1098	70
Dry out lot	204	13
Feed bunker of manger area	108	7
Costless-stall expanse	94	vi
Gratuitous-stalls	55	4

Icy or slick physical is ever a problem for free-stall herds. Concrete should be grooved or scabbled to provide traction. Moving cattle to a dirt lot or from one area to another non only provides a better surface only also provides added stimulation from the movement alone.

Feet and Leg Bug

Cows with sore anxiety or legs or poor structural conformation exhibit less mounting activity, or they stand up to be mounted when non in heat considering it is also painful to avoid being mounted. One British written report involving 770 cows with almost 1500 lactations showed that lameness caused by specific lesions on the hoof was associated with a 7-day increase in days to first service and 11 more days open up compared to herdmates without lameness. These differences were greater for cows with sole lesions that developed between 36 and 70 days postpartum, the fourth dimension when cows should first be detected in heat. For those cows the interval to first service and days open increased 17 and xxx days, respectively.

Cow Density

Data are non available for determining optimal number of open cows per unit area or total number of cows per pen to accomplish maximum expression of estrous behavior. Nevertheless, common sense would suggest that if cattle are forced into a crowded surface area, such as a holding pen associated with a milking parlor, that mounting activity would be suppressed or cows would be forced to stand up to be mounted fifty-fifty when they are not in oestrus. Too oft the simply time cows are observed for rut is when they are in belongings pens prior to milking. In overcrowded free-stall barns, cows may stand to be mounted in a stall or alley simply because they cannot escape a mounting cow. Crowded conditions also may increase the incidence of false-positive heats determined by rump-mounted heat detection devices or markings.

Temperature

Research conducted in Virginia showed that as maximum daily temperatures increased to about 75°F, mounting activity also increased. Only at temperatures to a higher place 85°F, beyond the comfort range for cattle, mounting was less frequent. Enquiry washed at Purdue University suggests that cows in cold weather take more than mounting activity than cows exposed to hot weather; however, during hot weather estrous cows tend to exhibit more than secondary signs, such as rubbing, licking, and chin resting.

Variation During the Day

Do cows adopt to mount other cows at a certain time of 24-hour interval? Herd managers oftentimes remark that most mounting occurs in early morning or during the later evening hours. In a study conducted in Canada, video cameras monitored estrous activity in a complimentary-stall area 24 hours a day. This written report showed that nearly 70 per centum of the mounting occurred between seven p.m. and 7 a.m. (Figure 2). This observation suggests that cows are most likely to exhibit mounting activity when they are not distracted past farm activities such equally feeding, milking, and barn cleaning. The data may farther indicate that cattle prefer to mount during the cooler times of twenty-four hour period.

Figure 2. Upshot of time of twenty-four hour period on mounting activity for estrous cows. Adapted from Hurnik et al. (1975)

Herdmate Condition (Stage of Estrous Bike)

To determine the cause of silent heats or poor expression of heat, consider the overall reproductive status of the herd and compare the ratio of open to significant animals in each grouping of cows and heifers. Pregnant cows are the least likely group of herdmates to mount a cow in heat. Herd managers must rely on the other open cycling herdmates to detect heat. What about the other nonpregnant herdmates? Do herdmates vary in their ability to detect and mount cows in rut? Does the twenty-four hour period of the herdmate's estrous cycle influence her interest in the estrous cow?

When Penn State researchers conducted a very controlled study, estrous cows encountered each of xix cycling herdmates in an isolated barn i-to-ane for 10 minutes. The total number of mounts past each herdmate was determined on mean solar day 10, day xv, day of heat, and day 5 of the next cycle. Herdmates varied in mounting activity, as did estrous cows in attracting mounts. More important, for the herdmates every bit a group, the number of mounts differed substantially with the day of the bicycle. Herdmates in midcycle (day x and twenty-four hour period fifteen) and on twenty-four hour period five averaged one mount or less during the ten-minute observation flow. Some herdmates did not even mount the estrous moo-cow on those days. Still, when the herdmate herself was in estrus, the number of mounts averaged 2.5 during the ten-minute flow. Thus, taken equally a group, cows are poor heat detectors in the middle of their wheel. Since this represents 50 to 60 percent of the estrous cycle and reduces the number of effective heat-detecting herdmates by a similar percentage, managers must rely on cows in or virtually heat to notice other estrous cows.

In some herd situations, a few open up cycling cows may contribute to the problem of silent or missed heats. In modest herds, most of the herd may exist pregnant at certain times, and the stage of the cycle of the few nonpregnant cows may exist such that they are not effective heat detectors. As more animals go pregnant, the number of potential heat-detecting animals is reduced. The situation is similar for herds that freshen on a seasonal basis. After an intensive breeding catamenia, when a loftier per centum of the herd is pregnant, information technology becomes increasingly difficult to identify the few open cycling cows in heat. There but may non be enough herdmates in the proper stage of the cycle to collaborate with an estrous cow. A 3rd situation may occur frequently in free-stall herds where cows are grouped according to production. Mostly, the lower production group contains pregnant cows, merely because of low production, some nonpregnant cycling cows may be included in this group. Information technology becomes very difficult to detect the cows in heat considering their herdmates are pregnant.

Number of Herdmates in Proestrus or Estrus

Frequency of mounting is considerably college when more ane cow is in oestrus or budgeted heat (proestrus) at the same fourth dimension. Canadian scientists found that the number of mounts increased significantly when two or more cows were in rut simultaneously (Table 3).

Tabular array 3. Effect of number of cows in oestrus on mounting activeness.
Number of cows	Average mounts per moo-cow in heat
Source: J. Hurnick et al.(1975), Applied Animal Ethology 2:55.
1	11.two
two	36.half dozen
3	52.6
4 or more	49.8

Nutritional Factors

Mounting activity and other sexual beliefs accept been shown to subtract in cows that lost more weight since calving than herdmates with minimal weight loss. On the other hand, in that location are certain cows within the herd or entire herds in which the majority of the cows are truly anestrus (noncycling). Possible causes of anestrus include poor body condition, anemia, uterine infection, cystic ovaries, and parasitism.

Lactation Number, Days Postpartum, and Milk Production

With the possible exception of heifers, lactation number does not seem to affect estrous behavior. Variable results have been obtained from research comparing estrous beliefs with level of milk production or number of days postpartum. These factors have much less influence on the expression of estrus than other factors described above.

Estrous Detection Program

Heifers on dirt lot with practiced ground.

Apply your time efficiently, observing for oestrus when cattle are probable to mountain.
Allow cows to interact, especially during the evening and early morning hours, when virtually of the mounting activity occurs. Even though loose housing systems provide more than time for cow interaction, be sure to detect the cattle oft. Move pastured cattle to an surface area where they hands can be observed. In conventional housing systems, turn cows out twice daily for twenty to 30 minutes. Exist certain to turn cows out when fourth dimension can be spent observing them. Avoid scheduling observation periods at feeding time or during the warmest hours in summertime.

An aggressive rut detection program can be effective. A Pennsylvania study involving approximately 200 repeat breeding heifers (3 or more services) compared the average and distribution of cycle length based on farm records before the heifers arrived at the enquiry station with these estrous bicycle characteristics after inflow. The major difference in management was that the heifers were turned out for heat detection at 8:00 a.m., iv:00 p.m., and midnight. The average duration of cycle length and the frequency of long cycles were reduced. The onset of heat occurred equally for the three heat detection periods. Table 4 shows that the more than frequent the observation, the more heats are detected.
Slippery and dingy weather condition severely inhibit mounting activeness. Provide an area with a good footing surface where cattle are gratis to collaborate and where few obstacles hinder motion. Moving cattle to a separate area for oestrus detection may stimulate estrous behavior.
When cows have sore feet and legs, heat detection is more hard. Minimize this trouble by trimming hoofs periodically, and care for infected feet as soon every bit a trouble is apparent.

Cows on grooved concrete.
When several people are working with the herd, assign one person to be responsible for heat detection, and let time for employees to practice the job properly. Train employees to recognize signs of heat and promptly written report this data to the responsible person. Consider having a financial incentive program to increment estrus detection efficiency.
Studies take shown that up to 15 pct of the cattle presented for insemination are really not in rut. Poor cow identification can be one crusade of this problem. Legible neck chain numbers, large ear tags, and freeze brands tin can aid in accurate identification and can reduce mistakes.
Record all heats, whether the animal is to be inseminated or not. Heat detection volition improve if future heats can be anticipated. Apply a pocket notebook to record heats and other data. Transfer information to a rut expectancy nautical chart and to the permanent individual cow record. This permits monitoring of abnormally long cycles and long intervals from freshening to commencement service.
Consider using heat detection aids to assistance increase the number of heats detected. Detection devices and detector animals should supplement routine visual ascertainment.
In larger herds the employ of a testosterone-treated heifer will stimulate more mounting and probably volition be price effective.
Using prostaglandin to induce estrus in one or two cows volition increase the overall estrous beliefs in the herd.
Estrous synchronization programs for the lactating herd, or programmed breeding, will synchronize estrus for several days. Likewise, more than heats will exist anticipated and thus more heats are likely to exist observed.
Isolate the cow thought to be in heat with a sexually active cow or rut-detector brute. Heat may non be detected in some cows in a large grouping situation, simply when isolated with an active cow or heifer, a moo-cow possibly in heat may exhibit continuing behavior.
Watch for sexually active groups of cattle. Cows in proestrus or estrus tend to congregate and stay together.
Adjust the feeding program so that cows calve in proper body condition and weight loss is minimized during lactation.

Table 4. Comparison of estrous cycles of repeat breeding heifers earlier and during an intensive heat detection programme.
	Average interval between heats	% short cycles <17 days	% normal xviii-24 days	% long cycles >24 days
Source: T. Tanabe and J. Almquist (1960), Penn Land Research Bulletin 672. ¹ Heifers observed at 8:00 a.m., 4:00 p.m., and midnight.
Before	48.half dozen	6.three	41.9	51.8
During¹	20.half-dozen	9.9	81.i	9.0

Group of sexually active cows.

Timing of Insemination

Cow with large ear tag for easy identification.

Ovulation occurs 25 to 32 hours afterwards the onset of standing heat. Standing beliefs is the but reliable symptom producers have to determine time of ovulation.

Sperm have to exist in the female person reproductive tract for approximately six hours earlier they are capable of fertilizing the egg. This process is termed capacitation. Although live sperm have been found in the female person tract up to 48 hours subsequently insemination, sperm viability usually is estimated to be 18 to 24 hours. Improper semen handling or poor insemination technique can dramatically reduce the number of sperm cells available for fertilization and thus can lower the conception charge per unit.

The egg travels very rapidly from the ovulation site to the fertilization site in the oviduct. The fertile life of the egg is shorter than that of the sperm. Ovulated eggs remain fertilizable longer (10-twenty hours) than they remain capable of being fertilized and developing into normal embryos (8-10 hours). The likelihood of embryonic death increases every bit the time beyond this interval increases. Thus feasible sperm should be at the site of fertilization awaiting the arrival of the freshly ovulated egg. Convenance either also early on or too late allows an aged sperm or an anile egg to interact at the site of fertilization and will result in poor conception. Events and time intervals associated with standing oestrus and insemination are summarized in Figure 3.

Figure three. Average time relationships among reproductive events.

Cattle should be inseminated during the last one-half of standing estrus. The a.one thousand.-p.m. rule was adult every bit a guide. Cows commencement seen in standing estrus in the morning time (a.chiliad.) would be inseminated in the afternoon (p.grand.) and those observed continuing in the evening would be bred the next forenoon. This system was based on research in which cows were observed frequently (4 to 12 times per mean solar day), immune to interact, and exhibited mounting/standing behavior. Furthermore, insemination was based on continuing heat, not secondary signs. Under such conditions, heat detection was very good. Merely herd managers may not be in a position to accurately predict the latter one-half of the heat catamenia. Generally information technology is a challenge simply to observe standing behavior. Knowing when to inseminate is some other direction challenge.

More recent studies conducted by bogus insemination organizations and universities reexamined timing of insemination. In a Virginia study with twice daily heat checks, cows were inseminated either at the cease of the estrus check menstruation in which they were beginning observed in heat or at the end of the adjacent oestrus cheque period. Using a routine 8:00 a.grand. and viii:00 p.chiliad. heat detection organisation, waiting 12 hours to inseminate resulted in a slight numerical advantage in pregnancy charge per unit over inseminating immediately after rut was commencement observed (55% vs. 51%). However, this was not a meaning departure. Thirty percentage of the cows stood to be mounted at the 12-hour oestrus bank check after they were outset observed in standing rut. These cows had higher pregnancy rates than their herdmates, whether they were inseminated immediately after existence first observed in heat or 12 hours subsequently.

Results from a field study in New York showed that near optimal fertility was obtained with a unmarried morning insemination of all cows in heat from the previous evening, including those in heat that morning time. This result suggests at that place may be a benefit to before breeding nether farm conditions.

Applying this information to a herd situation suggests the following guidelines:

Best fertility is obtained when cattle are inseminated during the last one-half of standing rut.
If a management schedule permits routine heat checks and if it tin can make up one's mind when a heat began and thus predict the latter portion of the estrus, the a.1000.-p.m. system should be used.
If the conception rate is unsatisfactory or heat detection is not routine, cows should exist inseminated soon after they are showtime detected in standing rut. Waiting 10 or 12 hours probably results in most of the cows being bred too late.
Remember, factors other than timing of insemination can affect the formulation charge per unit.

Milk Progesterone Analysis as a Tool for Rut Detection

The concentration of progesterone in blood is correlated closely with levels found in milk. The relative relationship between milk and blood concentrations is the same. Progesterone is low during proestrus and during oestrus. Information technology begins to rise slowly subsequently ovulation as the CL develops.

Verifying suspicious heats

If the herdsperson is suspicious that a cow is in heat, milk progesterone concentration can be used to verify that the cow is in or near heat. Such testing may exist useful in the following situations:

The cow was observed in heat, but was previously diagnosed pregnant.
Standing heat was observed, merely the interestrous interval was abnormally long.
The cow was detected in heat based solely on secondary signs.

Evaluating estrus detection accuracy

Numerous studies using milk progesterone analysis accept shown that five to 15 percent of cows are inseminated when they are non in or near oestrus. Milk progesterone testing can be a reliable method of evaluating the accurateness of heat detection on an individual farm. To make the evaluation worthwhile, 15 to twenty cows should be sampled on the twenty-four hours of insemination. Milk samples should be obtained at the milking immediately after insemination. When compared with a standard progesterone sample, the milk obtained on the day of insemination should have low progesterone.

If more than 5 percent of the samples take high progesterone, the heat detection error rate is too high. A few samples may have intermediate concentrations of progesterone, suggesting that it may be declining, but has not yet reached a minimal level, or that it is rising and low concentrations already have occurred. No definitive estimation can be fabricated from such results.

Dairy producers and veterinarians must realize that progesterone is low for about six days around the time of oestrus. Thus low progesterone indicates the moo-cow is either in or most oestrus, but progesterone levels cannot be used to precisely time the insemination. Errors in heat detection should be considered the primary cause of low conception in trouble herds. Milk progesterone analysis is a tool to help determine whether a heat detection trouble exists.

Evaluation of Heat Detection Efficiency

Complete and accurate records including all heats, services, and veterinary examination findings are needed to calculate heat detection efficiency. Some DHIA processing centers and herd management computer programs provide a rut detection index.

There is a difference betwixt the accuracy and the efficiency of oestrus detection. Inaccurate oestrus detection occurs when cattle are inseminated only are not in truthful oestrus. Inefficient heat detection simply refers to too many unobserved or missed heats. Many reproductive trouble herds experience both inaccurate and inefficient rut detection.

Characteristics of Herds with Oestrus Detection Errors

Estrous intervals between 3 and 17 days exceed 10 percent.
Estrous intervals between 25 and 35 days exceed 10 to xv percentage.
Cows inseminated 1 mean solar day and once more within three days exceed 5 percent.
Several cows are checked pregnant to a service earlier than the concluding one recorded.
Several cows calve normally three to six weeks earlier the expected calving date.

Characteristics of herds with missed heats

Very few heats are observed and recorded before first service.
Average days to first service exceed 80 days when the voluntary waiting menstruum to start service is 60 days.
Average interval between breedings exceeds 30 days.
Estrous intervals between 38 and 45 and 55 and 65 days exceed 15 pct.

Estrous detection goals

85 percent of the cattle are detected in estrus by 60 days postpartum.
Days to first service are 75.
threescore percent of the estrous intervals are between 18 and 24 days.
Ratio of the number of 18-24 to 36-48 day estrous intervals exceeds 4:i.
At least 70 percent of the heats are detected.

Heat detection efficiency equations

Several methods are used to express efficiency of estrous detection. These indexes are used to express the percentage of cows detected in heat relative to number of cows actually in heat. They provide an guess of the intensity of estrous detection just do non measure accuracy. The frequency of prostaglandin utilise to induce estrus and shorten the interestrous interval should be considered when evaluating these indexes.

Per centum of Possible Heats Detected

The full number of services and reported heats for a group of cows during a specified period of time is divided by the full days in the period divided by 21. This is virtually useful in a beefiness cattle breeding programme.

Example: If twenty heats were observed in a group of twoscore beef cows over a 24-twenty-four hour period period, the estimated per centum of heats detected would be calculated equally follows:

Percentage of Breedable Heats Detected

A breedable heat is defined as any oestrus occurring across the voluntary waiting period for a specific herd. The voluntary waiting period (VWP) is the interval of time from calving until the manager is willing to rebreed the cattle. The number of breedable heats can be estimated by this formula:

If the VWP were l, the starting time breedable rut beyond fifty days would exist detected on the average at twenty-four hour period 60 postpartum (10 days is half an estrous cycle). The percentage of breedable heats detected tin and so exist estimated past the formula:

If this index is to exist accurate, all observed heats must exist recorded. The percentage of breedable heats detected is not afflicted by formulation rate or the conclusion to delay breeding.

Rut Detection Index (Efficiency)

Several formulas have been developed to determine the efficiency of heat detection.

Interestrous interval method: normal cycle length is divided past average interval between consecutive services or heats for all eligible cows.
Example: 21 ÷ 32 x 100% = 65.6%
Breeding interval (BI) methods: These are proficient indicators of heat detection efficiency after first service. DO refers to days open. (Table 5 shows pct of heats detected.)
1. 1. Pregnant Cows
  1. a. Breeding interval method using days to first service:
  2. b. Convenance interval method using voluntary waiting menstruum (VWP):
2. 2. All cows serviced (services per cow) Services per moo-cow includes average number of services for significant cows, cows examined for pregnancy and found open, and cows serviced with at least 45 days elapsed since convenance, but not all the same examined for pregnancy.
  1. a. Breeding interval method using days to first service:
  2. b. Convenance interval method using VWP:
    Example: days open = 126, days to first service = 85, and services per cow = 2.0
    
    % heats detected (Tabular array v) = 51%

Tabular array 5. Interpretation of percentage of heats detected based on breeding interval.
Convenance interval	% of heats detected
D. Grusenmeyer et al. (1983), Western Regional Extension Publication 67.
23	91
26	81
thirty	70
35	60
41	51
l	42
60	35

If complete information including days to first service, days open up, and conception rate are available, Table 6 on the next page can be used to estimate rut detection efficiency.

Tabular array half dozen. Interpretation of per centum of heats detected based on boilerplate days to commencement service, formulation rate, and days open (use tabular array that best fits average days to showtime service in herd).
60 days to kickoff service (boilerplate between 50 and 70 days) Conception rate (%)
Source: One thousand. McGilliard et al. (1979), Dairy Guideline 54: Evaluating Rut Detection, Virginia Polytechnic Institute and State University. Annotation: In developing these tables, all cows were assumed significant by 200 days.
Always days open	35	40	45	50	55	60	65	70
150	33	28
140	42	37	33	29
130	52	45	twoscore	34	33	thirty
120	63	55	51	45	xl	37	35	32
110	77	68	60	54	49	45	42	39
100	93	83	73	66	60	55	51	47
90			90	82	74	68	63	58
80					93	85	eighty	74
70 days to first service (average between 60 and 80 days) Conception rate(%)
Always days open	35	40	45	l	55	lx	65	70
160	29
150	39	33	30
140	49	43	38	35	32	28
130	62	53	48	43	39	34	33	31
120	75	66	58	53	48	44	40	38
110	93	82	73	65	60	55	50	47
100			90	81	73	68	63	58
90					93	86	79	73
80 days to get-go service (average betwixt seventy and 90 days) Conception rate(%)
Always days open up	35	forty	45	l	55	lx	65	70
160	34	30	27
150	45	twoscore	35	32	28	26
140	58	51	45	41	37	34	32	29
130	73	64	57	52	47	43	twoscore	37
120	91	lxxx	72	64	58	54	49	46
110			89	80	73	67	62	58
100					93	85	79	73
90 days to first service (average between fourscore and 100 days) Conception rate(%)
E'er days open	35	twoscore	45	50	55	60	65	seventy
170	29
160	41	36	31	28
150	54	48	42	38	35	32	29	27
140	lxx	62	54	49	45	41	38	35
130	89	78	70	63	57	52	48	45
120			88	80	72	66	62	57
110					93	85	78	73

Estrous Detection Aids

Records

No matter which record system is used, the information should be posted and available to all farm employees. The more people anticipating and watching for the oestrus, the more likely oestrus detection efficiency will exist maximized. All heats, including those observed in the early on postpartum catamenia, must be recorded. Finally, record systems should be used on a daily ground.

Oestrus Expectancy Chart

Special calendars are bachelor from bogus insemination organizations. Most charts are organized on a 21-day cycle so that futurity heats can be anticipated. Some herd managers mark day 19 following insemination and then that the expected heat can be anticipated several days in advance.

Breeding Bicycle or Herdex Record Organization

These wall-mounted reproductive record systems employ color-coded pins or markings to indicate reproductive events for each cow. By either turning a transparent plastic dial or sliding the plastic cover on a daily basis, future heats and reproductive events tin be anticipated.

Computer Generated Activeness Lists

Some dairy management calculator programs tin generate listings of cows that require special attention or activity on a specific day. Activity lists indicate cows to scout closely for render heats or cows that have non yet been observed in heat.

Prostaglandins

If more than 1 creature is in proestrus or estrus simultaneously, mounting behavior increases and standing behavior is more than likely to be observed. Depending on herd size, it may be worthwhile to inject ane or more cows with prostaglandin at various intervals during the calendar week to induce more than estrous behavior in the herd.

Mount detection aids

Studies have confirmed that using conventional mountain detectors such as Kamar devices and tailhead markings without visual observation for estrous results in lower pregnancy rates. However, normal pregnancy rates and improved heat detection efficiency are obtained when mount detector systems are used to supplement visual observation.

Kamar Pressure-Sensitive Mount Detectors

These devices are glued on the topline of the rump forrard toward the hooks co-ordinate to the size of the cow. Sustained pressure for several seconds by the sternum of the mounting cow will miscarry carmine fluid from a small storage sleeping accommodation into a larger visible plastic chamber. The detectors should be placed further forward on small-scale cows to avert fake activation when large cows try to mountain them.

The devices can be used for diverse groups of cattle. To help detect early on postpartum heats, they can be applied to cows at 30 days postpartum. Some managers use them to detect rut for cows non observed in heat by the voluntary waiting catamenia (xl, l, or lx days). Several days subsequently a heat or insemination, the devices are put on cattle in an try to detect evidence of mounting activity during the adjacent render estrus. They can be helpful in detecting heat afterward an estrous synchronization program has been established.

Follow these guidelines when using mountain detectors:

Store detectors and adhesive in a cool, dry environment.
Apply properly according to the size of the animal; don't use an excessive corporeality of adhesive.
Write the cow's ID on the detector. If it comes off, the moo-cow can be identified and observed carefully for other signs of heat.
Do non clip hair or apply the adhesive to moisture hair.
Get out partially activated, or "triggered," detectors on the cows for several boosted days. These cows may be in proestrus.
Remove obstacles such as depression branches, cattle dorsum rubbers, and oilers from the pasture, do lot, or free-stall barn. Such items tin can exist rubbed and tin can actuate the mount detector. This would result in a false positive.
Exist aware that the orientation of certain partitions and stall dividers tin can inadvertently activate these devices.

Falsely activated detectors may as well exist an indication that the devices were practical as well far back on small animals. Simulated positives are more than frequent when cattle are confined in crowded pens or when cattle infested with external parasites rub or scratch their backs. Fractional activation may upshot when an animal is trapped in a mounting state of affairs but is non in heat. Conscientious interpretation is essential to efficiently employ mount detectors. Tabular array 7 compares the pregnancy rates amongst groups of beef cattle with fully activated, partially activated, or missing detection devices at the time of appointment insemination 80 hours after prostaglandin injection. Cows missing devices or with fully activated detectors had significantly higher pregnancy rates compared to cows with partially activated detectors.

Table 7. Pregnancy rates post-obit eighty 60 minutes date insemination later prostaglandin for cattle with fully activated, partially activated, or missing Kamar detectors at time of insemination.
Detector status	% pregnant
Source: C. Marshall et al. (1978), Proceedings of the Extension-Industry Workshop on Beef Cattle Reproductive Direction.
Fully activated	67
Partially activated	23
Missing	51

Tailhead Markings

Mark the tailhead with chalk, paint, or crayon and observing for bear witness of rubbed off or smeared markings is less expensive than Kamar detectors and has gained popularity in larger herds. Markings 10 to 12 inches long and 2 to 3 inches wide are made across the tailhead with a livestock marking crayon or heat detector pigment. Tailhead pigment is less user-friendly to use than crayon simply lasts longer (up to three weeks). This system works well-nigh effectively in loose-housing arrangements where cattle can be restrained in self-locking headgates to be marked or observed for evidence of smeared or rubbed-off markings, which indicate the animal was mounted. Markings tin can besides exist touched upward at this time.

False positives can occur for rea- sons similar to those with Kamar detectors. Cattle may need to be remarked every three or iv days. 1 subconscious advantage of this system is that when mark or examining the rump region of the cow, the managing director may notice mucus belch, smeared mucus on the tail, swollen and reddened vulva, abnormal vaginal discharge, or metestrous bleeding. In larger herds many of these symptoms go unnoticed. Tailhead marking is inexpensive and big groups of cattle can be marked in a short period of time.

Electronic Mountain Detectors

Mount detectors are beingness developed which find and record legitimate mounts. Each detector is coded with the cow'south identification number, and the data is transmitted to a reckoner to be stored. At regular intervals during the day, the herd manager can access the information to decide which cows were mounted at a item time. Various prototypes are currently beingness tested.

Videotape

This system has been used extensively in research to continuously monitor estrous behavior. The cattle must be clearly identifiable from a distance and must be allowed to interact in a loose-housing arrangement. The video photographic camera(s) should monitor a big proportion of the housing surface area. Several cameras may have to exist strategically positioned, and the video equipment should be protected from moisture. This arrangement will be effective only if the videotapes are reviewed daily, peculiarly afterwards the herd has been monitored in the evening. The disadvantages are the initial investment for purchase and installation of the equipment and the time required to review the tapes. If used properly, however, videotaping is a very efficient and accurate estrous detection organization.

Heat detector animals

Heat detector animals can reduce the days to beginning service and can improve estrous detection in the herd if they are used properly and supplement visual ascertainment. However, managers must realize that on an individual ground, surgically altered bulls or hormonally treated females vary in their sexual aggressiveness.

In general, such animals have been shown to be constructive in detecting oestrus. The more animals sexually active at one time, the more mounting will occur with each moo-cow in heat. If immune to interact with the herd throughout the day, detector animals provide a continuous monitoring of estrous beliefs. If stanchioned cows are turned out daily for heat detection or cows in loose-housing are checked regularly for estrus but heat detection does not seem to be effective, then utilize of a estrus detector animate being should exist considered.

Male person Event

Research has shown that in a beefiness herd the introduction of a bull shortens the interval to first rut during the early postpartum period. The physiological mechanism for this event is unknown.

Vasectomized or Surgically Altered Bull

A vasectomized bull or a balderdash with a surgically altered penis can be an effective heat detector. These animals can exist most effective if they are equipped with a mentum-ball or ballpoint marker harness which marks the loin and rump of cows that were mounted with a bright-colored mark solution. Surgically altering the penis of a bull to preclude intromission may exist more costly than vasectomy, but this method is preferred since vasectomized bulls can copulate with cows and mayhap spread illness.

With either method of preparing a bull, the animal will seek out cows in proestrus and estrus and possibly stimulate the overall estrous action in the herd. These animals can be used with beef cattle to stimulate early estrous activity (male consequence) and then be removed from the herd to let natural service to commence or they tin can remain with the herd for enhanced heat detection during an artificial insemination programme. The major disadvantage is the danger of handling a bull and allowing him to collaborate with farm employees. There also is the veterinary toll of performing the vasectomy or surgical alteration and general veterinary costs of maintaining the bull.

Testosterone-Treated Female

Testosterone, a male person hormone, causes increased sexual aggressiveness when injected or implanted into cows or heifers. Potential nonlactating cull cows or heifers, even freemartin heifers, are candidates for masculinization. Most people who have used this system prefer cows that have completed a lactation. Even so, in that location are several reports of success with freemartin or virgin heifers. A typical treatment regime consists of administering 200 mg of testosterone propionate intramuscularly every other day for three weeks. Some veterinarians have used larger doses (500 to 600 mg) once weekly or a unmarried injection of two grams of testosterone enanthate in corn oil given in three or four locations. When mounting activity is increased following these initial injections, the moo-cow is given a maintenance injection of about 500 mg testosterone propionate, enanthate, or repository testosterone every 10 to xiv days.

The interval between maintenance (booster) injections should be adjusted on the basis of sexual action of the detector animal. Some veterinarians prefer to use several Synovex-H implants for a maintenance program. These implants contain testosterone and estradiol.

The results of a trial comparing heat detection methods of routine visual observation by a herdsperson with utilize of a surgically altered bull or a testosterone-treated cow are presented in Tabular array 8. Although non a significant number, more heats were detected in the group of cattle with the testosterone-treated cow. Formulation rates were like for all groups.

Tabular array 8. Percentage of cows detected in heat and offset-service formulation rate for beef cattle detected in rut by three different methods.
Method	Number	Percentage detected	Conception rate
Source: T. Kiser et al. (1976), Journal of Creature Science 44:1030.
Herdsperson	31	67	62
Surgically altered bull	30	seventy	62
Testoterone-treated cow	29	84	67

The post-obit should be considered in using testosterone handling:

Testosterone treatment is an extra-characterization employ of this hormone. The FDA has non specifically approved using testosterone for this purpose. Guidelines must be followed on the withdrawal period before treated animals can be marketed.
While a large percentage of the females reply to the testosterone, some practise not.
It may be helpful to remove the estrous moo-cow from the group so that the detector moo-cow can search for other estrous cows.
Select a salubrious choose cow or heifer that has sound feet and legs and is large plenty to mount and marker other cows. Heifers must exist sexually mature. Practise non apply a lactating or pregnant animal.
Treated females tin be equipped with a chin-brawl marker harness or the herd can be marked with crayon, chalk, or heat detection paint or tin be fitted with mount detectors so that mounted cows can be identified.
This heat detection aid volition be effective merely when used in conjunction with routine visual estrus detection.
Maintaining a ratio of one treated female to every 30 open cows is necessary to maximize detection efficiency. In big herds, information technology may be beneficial to have more than than i detector animate being per herd. Such animals could be rotated on alternating weeks.
This arrangement can be constructive in both loose-housing and stanchion barn housing, provided cows are turned out and allowed to interact.
Avoid assuasive the treated animal to become overconditioned.
Testosterone-treated females in general are non dangerously aggressive.
Consult your veterinarian concerning the method of testosterone treatment.

Vaginal electrical resistance

In early on research done in Europe, the electrical resistance (ER) of vaginal fluids decreased during proestrus and through the estrous catamenia. Numerous studies have validated this concept. Several probes that measure the ER of vaginal fluids are now commercially bachelor.

Vaginal electric resistance probe.

Although the concept is physiologically sound, the claiming is to arrange this technology to a management situation. Resistance measurements vary amid cows; however, monitoring the relative changes within cows during the estrous cycle can provide the herdsperson with boosted information and can serve as a heat detection aid if cattle are probed frequently. One time the ER readings brainstorm to decline, the cow should be probed every 12 hours until the lowest reading is obtained. Theoretically, this reading coincides with the time of standing rut.

This tool is labor intensive since cattle must be probed oftentimes to detect significant changes in ER. The probe as well is expensive. It must exist washed in disinfectant, thoroughly rinsed, and dried before it is used in another moo-cow. Without proper sanitation, the device could spread affliction among cows.

Miniature electronic devices are being adult which are implanted into the vaginal tissue. They continuously monitor ER and transfer the information to a romote receiver and computer.

Activity monitors

It is well documented that cattle are more active during rut and thus spend more than time walking and standing than resting. Researchers at the USDA facility in Beltsville used pedometers to monitor cow activity between milkings. The study showed that activity increased approximately 400 pct during rut for cows housed in a free-stall barn, and 275 percent for cows in comfort stalls. During this study, 76 percent of the estrous periods were detected past visual observation and 96 pct were detected past changes in pedometer readings.

Since those initial studies, various pedometers have been developed and tested. Early prototypes were often inaccurate because of a high rate of imitation positive signals. Accuracy in identifying truthful estrous periods has improved in the newer models, which compare activity during a specified interval with activeness during the same menstruum on the previous day or the previous 3 days.

If pedometers are used properly and the equipment remains functional, this method can exist effective in identifying some silent heat cows which fail to evidence other obvious signs of rut. This heat detection aid tin can be effective if used in a herd environment where the devices are checked twice daily, excessive time is not devoted to cleaning mud and manure from them to observe the readings, and cattle are not agitated or moved excessively. Changes in direction activities that prompt excessive cow action on certain days tin can cause inaccurate readings.

Estrous detection in the future may involve electronic monitoring of mounting activeness, walking, or vaginal electrical resistance integrated into an automated telemetric system. At nowadays visual observation supported by proper employ of conventional heat detection aids is the near effective arroyo to estrous detection.

Glossary of Terms

Anestrus: absence of estrous cycles.

Corpus Luteum (CL): ovarian structure that develops at the site of ovulation during metestrus and continues to produce progesterone through diestrus and during pregnancy.

Diestrus: the period within the estrous cycle when the corpus luteum is functional.

Dominant Follicle: mostly the largest follicle within a wave of developing follicles which eventually suppresses the continued growth of other follicles. Toward the finish of the estrous bicycle, the ascendant follicle becomes the ovulatory follicle.

Estrogens: steroid hormones produced by cells within the follicle. Estrogen induces estrous behavior and muscle contractions with the uterus, oviducts, and cervix. Information technology too is involved in the initiation of luteinizing hormone release.

Estrous Cycle: the interval between two periods of estrus.

Estrus (Estrus): menstruum of time when the female person is receptive to mounting and will stand to be mounted by some other animal (continuing rut).

Follicle: the ovarian structure which contains the oocyte (egg). Equally follicles grow, a fluid cavity (antrum) develops. Cells inside the wall of the follicle produce estrogens.

Hormone: chemical agents secreted by endocrine glands and transported to target tissues, where they induce or regulate a specific physiological action.

Luteinizing Hormone (LH): i of the protein hormones secreted by the anterior pituitary gland and involved in the process of ovulation, corpus luteum formation, and role.

Metestrus: stage of the estrous cycle beginning immediately after estrus. Ovulation and early evolution of the CL occur during this menstruum.

Oocyte: also termed the egg. Contains the genetic material from the female. Information technology develops inside the follicle and is ovulated shortly after estrus.

Ovaries: primary reproductive organs where oocytes (eggs) develop within follicles during the estrous cycle. Estrogens and progesterone are produced by tissues inside the ovaries.

Ovulation: procedure of follicle rupture and release of the egg.

Proestrus: phase of the estrous cycle when the CL regresses, progesterone concentrations decline, concluding maturation of the dominant follicle occurs, and estrogen increases. During this stage, some secondary symptoms of estrus begin to exist exhibited.

Progesterone: steroid hormone produced primarily by the CL. Progesterone inhibits terminal maturation of the dominant follicle and the expression of oestrus, prepares the uterus for pregnancy, inhibits uterine contractions, maintains pregnancy, and aids in mammary development.

Prostaglandins: serial of lipid substances which produce hormone-like actions. Unlike near hormones, they are produced by many tissues through-out the body. With regard to reproduction, prostaglandin F2a causes regression of the CL during the later portion of diestrus. Prostaglandin is used for synchronization of oestrus.

Voluntary Waiting Period (VWP): the interval from calving until the herd managing director is willing to rebreed the cattle.

Wave of Follicular Growth: a group of developing follicles. Cattle may have two, three, or four waves of follicles that develop during the estrous bike.

Prepared by Michael L. O'Connor, professor of dairy science

This publication supersedes S282, Rut Detection and Timing of Service.

Source: https://extension.psu.edu/heat-detection-and-timing-of-insemination-for-cattle

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