The Heat Is On

Accurate Heat Detection -- The Key to a Successful AI Program

Eric Grant
Wahoo Productions, Inc., 905 E. Brittany Way, Highlands Ranch, CO 80126

How successful is your AI program? Getting the results you'd hoped for? If not, success may be just around the corner.

The most limiting factor in a successful AI program lies in the accuracy of heat detection. Pregnancy rate is usually the measure of a successful AI program. Pregnancy rates, however, are determined by a combination of accurate heat detection, inseminator efficiency, female fertility and semen fertility, with heat detection being the most important.

"The most fertile semen and the best inseminator in the world can't overcome the problems of inseminating cows at the wrong time," says Tom Geary, a researcher with USDA's Agricultural Research Service at Fort Keogh in Miles City, MT.

Visual heat detection is the most widely used method of detecting estrus in beef cows. But, Geary says most producers need to make some adjustments in their heat detection protocol in order to increase accuracy and efficiency.

"There are several reasons why we miss heats with visual detection alone," says Geary. "The main one is we don't spend enough time observing cows for signs of estrus."

To avoid inseminating cows at the wrong time, an estrous synchronization program can be very effective. Estrous synchronization can shorten estrus detection from a 21-day window to a five-day window. Not only does synchronization reduce the number of days spent visually appraising estrus, it also increases the accuracy of heat detection.

According to Geary's research and calculations, using estrous synchronization increases the chance of detecting each cow in heat by 10%. The reason is simple. If estrus is exhibited over 21 days, there will be only one or two cows in heat at the same time, and they have a hard time finding others that will mount them. If the estrus is exhibited over only five days, the number of cows in heat at one time increases, thus more mounts are observed.

Several estrous synchronization programs are available for beef females. They include MGA/PGF, Syncro-Mate-B, one or two-injections of PGF, and Select Synch. Each protocol has its advantages and disadvantages, so choosing a program depends on your animals, goals, facilities, and resources.

Time Of Observation Is Critical

Geary also believes that producers miss more naturally occurring heats than synchronized heats because of the time of day observations are typically done. The old standard for heat detection was 30 minutes of observation in the morning and evening. But, new research shows that while only 3% of synchronized cows were found to display heat during darkness, some 28% of natural estrus cows displayed heat during darkness.

"If every cow or heifer would remain in heat for 8-12 hours during which time they would actively engage in mounting activity, then perhaps this limited amount of heat detection would be sufficient," says Geary. But, cattle don't always perform by the book, so Geary suggests adding an additional observation period between noon and 6 p.m. This extra observation period will increase the percentage of cows and heifers observed in estrus, thus giving a better idea of when insemination should occur.

Geary also suggests producers make a larger commitment to heat detection. Research suggests that "intense heat detection" can be as accurate as electronic heat detection aids, such as HeatWatch. Intense heat detection requires a time investment of two hours each morning and evening, as well as one hour around noon. The extra time will pay off though. Geary found that "HeatWatch and intense visual observation were equally efficient in detecting heat among cows."

HeatWatch efficiently identifies 89-100% of beef cows and heifers within a herd that are in heat. Among those females, 88-100% are accurately identified, and, in fact, in heat. Visual detection of estrus (using the standard of 30-60 minutes each morning and evening) is just as accurate, but less efficient.

This means cows visually identified as being in heat probably are, but some that are in fact in heat are missed. Visual detection missed 22-31% of synchronized heats and up to 80% of unsynchronized heats.

Another management technique that may help observe heat in more submissive cows is to continue observations for signs of estrus for at least 30 minutes after removing cows that were observed to be in heat. "When there are several cows in heat," says Geary, "the more submissive cows often go unnoticed."

More accurate identification of the start of estrus increased conception rate and pregnancy rates. Conception rates were 62% using a 30-minute, twice daily observation program, while rates jumped to 82% when intense heat detection was used. Pregnancy rates doubled from 35% to 71% by using a more intense heat detection program.

Looking For The Signs

Although the only definite sign of estrus is "standing to be mounted," there are several other signs that may help observers pinpoint the animals to watch for estrus. The secondary signs of estrus include trying to ride, following, standing and putting her head on the back or rump of another female. Some cows also bawl, become restless, pace along a fence, and walk more in search of a bull. Clear mucus is sometimes seen on the buttocks or stringing from the vulva.

There are also tools on the market to help aid in visual detection of estrus. Remember, however, that aids should only be used to supplement visual observations. A list of the visual aids and their application can be found in Table 1.

Table 1. Visual Heat Detection Aids
Type Of Aid	Application	Detection Method	Cost
Kamar Detector	Applied with adhesive between tail head and hip bone over the sacrum.	It remains white until triggered by weight of mounting cow, then it turns bright red.	$1-2 / cow
Bovine Beacon	Glued to tail head of cow.	Contains fluorescent dye that glows in the dark when cow is mounted by another cow.	$1-2/cow
Painted/Chalked Tail Heads	Smear liberal amounts of chalk or paint on the tail head of the cow.	When chalk is rubbed off the tail head, the cow has stood to be mounted.	Less than $1/cow
Chin-Ball Marker	Marker device fits under the chin of a teaser (gomer) bull or androgenized cow.	An animal wearing the device mounts and slides off the cow in heat, leaving an ink mark on the back and hip of cow.	$150 plus ink

Teaser animals may be beneficial to producers in helping to detect estrus visually. Choices include a penile-blocked bull, vasectomized bulls, penis-deviated bulls, caudal epididymectomized bulls and androgenized females.

Your particular operation, estrus management plan and resources should be factored into whichever choice of teaser animal is used. Table 2 details the differences among the teaser animals.