Profitable reproductive performance of a dairy herd requires a quality heat-detection program that ensures routine and conscientious detection and proper timing of insemination.

This is especially true in large herds where it is almost impossible to visually examine every cow for estrus activity. Visual observation as the sole means of determining which cow is in standing heat would require four observation periods (ideally one every six hours) to detect the majority of animals expressing signs of estrus. The point is that heat-detection programs that rely exclusively on visual observation must be intense in the number of observation times per day and will still not identify approximately 20 to 30 percent of the cows in heat.

The tail-striping system has two components that allow detection of the maximum number of cows in heat:

(1) consistency – every day at approximate the same time every cow is observed and

(2) combines the primary and most reliable sign of estrus (standing to be mounted by a herdmate) with a quick visual inspection for secondary signs, such as mucus, ruffled hair on tail head, dirt over the back and flanks, swollen red and moist vulva, raw areas void of hair that may be bloody and sweaty areas between hooks and pin bones.

Why is the system effective?
Research at Virginia Tech using the HeatWatch system, allowing continuous 24-hour surveillance to monitor behavioral events associated with estrus, reported four characteristics of estrus that support tail striping as an efficient and effective system for heat detection. The average cow is mounted only nine times during standing heat. The second characteristic is standing heat or the time interval between first and last mount is slightly greater than seven hours, with one-third of the Holstein cows having a standing-heat period lasting less than four hours. Intensity of estrus expression was reported as the number of mounts per hour and classified into four categories (Table 1*). Two points should be taken from Table 1*:

(1) cows which should be easy to observe in heat represents approximately 8 percent of the total, and
(2) the conception rate is not related to the intensity or duration of estrus.

The third important characteristic is that the initial mount, or start of standing heat, is uniformly distributed during the 24 hours of the day, so just as many cows come into heat between 6 p.m. and midnight as between 6 a.m. and noon (Figure 1*). Finally, 95 percent of all cows ovulate between 17 and 38 hours after the start of standing heat with an average time of 28 hours. So the average heat period is short in duration with relatively little mounting activity occurring randomly during the 24 hours of the day. Ovulation or release of the ovum is also equally distributed. Therefore, there is no best time of day to inseminate cows in a commercial operation.

Another study conducted at Virginia Tech attempted to determine whether once-daily or a.m.-p.m. inseminations would increase conception rates. A total of 7,240 first services were evaluated across 166 dairy herds. Technicians within a service area were equally assigned to a particular A.I. program (once-daily or a.m.-p.m.) for a three-month period and switched to the other program for the next three months. This cross-over design was utilized to minimize effects of herd and season on conception rates. Once-daily A.I. was defined as a fixed three-hour period for A.I., whereas the a.m.-p.m. system consisted of cows first observed in heat during the a.m. and inseminated that p.m. or cows first observed in heat during the p.m. inseminated the next morning. The two programs did not differ with a 58.4 percent 90-day non-return rate for cows bred once daily and 57.8 percent for cows inseminated using the a.m.-p.m. guideline (Table 2*). Thus, conception rates were the same for both a.m.-p.m. and once-a-day insemination protocols.

Component of tail striping
Tail heads should be marked (chalk or paint) while the cows are restrained by lock-ups. For herds that do not have headlocks, it is important to get good application initially and then walk through the herd at a time of day when the majority of a pen are lying in freestalls, which usually occurs about an hour after feeding. However, the most efficient and accurate employment of tail striping occurs when headlocks are used; therefore, they should be encouraged. Herds that do not have headlocks or an effective method to inspect the marks and determine cows to be bred and re-apply chalk/paint present a challenge. But cattle will calm down and become familiar with the technician in time. Cross-over gates are commonly used to prevent circling of loose cows, and an extra gate is attached at the end of the lane to touch-up runners and cows that stay ahead of the technician during walk through.

Loose hair, dirt and dried manure should be brushed from the tail head prior to applying the chalk/paint. Apply a uniform stripe the width of the applicator about 6 inches in length on the top of the spine from the high point to the slope of the tail. Consistency of the mark is critical, allowing interpretation of chalk/paint to be easier. Chalk/paint should be re-applied as often as needed to maintain visibility, but it should still rub off easily with pressure from three to four mounts by a herdmate. An extra heavy chalk line will be more difficult to read, especially on questionable, low-activity cows.

Green chalk/paint is usually used to identify pregnant cows and a contrasting color, commonly orange, blue or pink, is applied to open cows to allow for both identification of reproductive status and faster inspection. Efficiency of the system comes in the fact that the technician is trained to evaluate the cow and make the decision to breed or not to breed in a matter of seconds. In some herds, different colors are used in each pen to serve as an easy identification when cows are mixed and not in the correct pen to allow re-sorting to the correct location.

Observing and working with experienced technicians that have made thousands upon thousands of decisions is the best and most effective way a technician learns how to make accurate and fast decisions of whom to inseminate. All new technicians, irrespective of background, should ride with a few tenured technicians until it is determined he/she is “ready” to make these critical decisions in a timely and accurate manner. With a trained eye, the technician determines which rubbed-off markings are the results of legitimate mounting activity and which were licked off or worn off naturally, and this maximizes the reproductive and genetic potential of using semen from a genetically superior sire.

Evaluation of heat-detection program
Accurate records are necessary to obtain the history of past performance and determine if changes or adjustments need to be made in current management policies. However, one must use good judgment with monitoring to avoid changing something when it is not really a problem. The objective of evaluating the heat-detection program is to look for opportunities to improve the level of herd performance either by accomplishing the task better or more efficiently. The on-farm computer software should allow an appraisal of not only how well cows are conceiving, but also how the breeding interval, breeding code (reason why that cow was inseminated), A.I. technician and the interaction of these factors affect the conception rate of the herd.

Table 3* is an example of the DairyComp Bredsum report by interval analysis. The two items to evaluate are percent Tot, which is the distribution of breedings by each interval grouping, and the percent Conc, which is the conception rate for that specific heat interval. My benchmarks are to have a minimum of 30 percent in the normal 18 to 24 days category, less than 10 percent in the 4 to 17 days grouping, which usually represents cows that are off cycle, and approximately 5 percent in the short 1 to 3 days rebred category. The short- cycle interval (1 to 3 days) can contain up to 15 percent if the percent Conc is similar to the percent Conc for the normal cycles (18 to 24 days). Usually the 4 to 17 days category has the lowest percent Conc. Cows suspected in heat with an off-cycle interval of 4 to 17 days should have additional questions asked prior to deciding to inseminate, such as: When was the last breeding to a timed A.I. protocol or natural heat and what additional secondary signs is she expressing to confirm breeding. The 18 to 24 days interval should have both the greatest number of inseminations and the highest conception rate.

Table 4* is an example of the DairyComp Bredsum report by breeding code. Breeding codes should be limited to the major reasons why cows are inseminated. A periodic review of this report can determine if various first-service and resynchronization protocols are obtaining acceptable conception rates or if breeding protocols need to be changed. The “other” category represents cows too early to determine if they are pregnant or open and cows that may have left the herd.

Table 5* is an example of the DairyComp Bredsum report by technician. Table 6* is an example of the DairyComp Bredsum report that gives the 95 percent confidence interval and the interaction of technician and breeding code. These two reports should be used together to determine if the conception rates obtained by technicians are similar and if they are influenced by the reason cows were inseminated. In Table 6*, Rick has the lowest conception rate of 26 percent, but it is due to cows that he inseminated when reading rubbed chalk marks (24 percent), not Ovsynch breedings (34 percent). The recommendation would be that Rick work with either Freddy or Miguel to make better decisions on which cows should be inseminated based on rubbed chalk marks. Secondly, we are 95 percent certain that Rick’s conception rate is lower than both Freddy’s and Miguel’s because there is no overlap in the 95 percent CI Total category. Rick has the largest 95 percent confidence interval because he only has 5 percent of the breeding, whereas each of the other technicians has approximately one-third of the breedings. We can be 95 percent confident that Rick’s conception rate is between 22 and 31 percent, where Freddy for example is between 33 and 37 percent.

Tail striping raises the heat detection rate because visual observation of every cow occurs consistently with a systematic procedure. Labor is maximized because, in most situations, a walk-though takes only 15 to 20 minutes to observe a pen of 150 to 200 cows. Using tail striping during the pre-synchronization protocol period after the voluntary waiting period identifies cows that are cycling and can be inseminated, thus saving labor and cost of hormone injections required for the timed A.I. portion of the protocol. Catching natural heats increases palpation pregnancy rates and reduces the number of cows that need to be enrolled in a resynchronization protocol following a pregnancy examination.

A pregnancy is fundamental to milk production and supplies calves for the heifer replacement program. The value of getting a cow pregnant has never been more important than it is today. The average value of a pregnancy has been reported to be approximately $750. Tail striping consistently delivers high heat detection rates and, combined with professional technician insemination service, high pregnancy rates can be obtained. PD

Firgure and Tables omitted but are available upon request to editor@progressivedair.com.

Dr. Ray Nebel
Senior Reproduction
Specialist with
Select Sires
rnebel@selectsires.com