by Whitney Whitworth, PhD.

Artificial insemination (AI) can be one of the most powerful tools used on a ranch. It allows for use of supreme sires, control of possible disease transmission, and reduces the need to buy and keep as many bulls. It does require a great deal of planning, special training, and special facilities. If there is any area that most operations can improve on, it is in heat detection.

Early in the history of the use of AI, it became apparent that timing of the insemination was critical to the success rate of procedure. Research conducted at the University of Nebraska in the 1940s by George Trimberger gave rise to the “AM/PM rule,” which is what most producers have adhered to for quite some time. If a cow is observed in heat in the morning, she will be bred approximately 12 hours later. Or, if she is observed in heat in the evening, she will be bred the following morning.

There is no substitute for observation of cattle in the AI process. In order to find animals in heat, no less than one hour each morning and one hour each evening should be dedicated to watching the females for signs of standing estrus. Personnel should be trained to look for signs of females coming into or going out of heat. Fortunately, with synchronization techniques currently available, it is easier to group cows together to offset some of the time and labor necessary to inseminate a group of cows. When females are coming in to estrus, or going out for that matter, they will group together with females in heat in what are referred to as sexually active groups or SAGS. These females will often be in small groups away from the rest of the herd. They will be very active, walking and riding each other. The females who are actually in heat will stand to be ridden by other cows, usually for several seconds at a time. Their stance will be somewhat rigid, and they will not try to walk away from the other cows riding them. If a cow moves away when another animal attempts to ride or doesn’t remain still for a measurable few seconds, she is not in heat at that time. Again, observation is important.

Obviously, animals cannot be observed 24 hours per day and of course there is always the possibility they will be in heat when no one is watching them. There have been a variety of techniques which have been successfully used to aid in observation of estrus. The simplest and cheapest way is to use livestock marking chalk. Cattle are marked with a heavy amount of chalk on the top of their spine from approximately their hooks to their pins. When observation time comes around, it is easy to see which animals have been active, as the paint will be disturbed. Watch for other signs too, like dirt on the flanks from cows riding them and ruffled tail hair. Sometimes the paint can be disturbed by tree limbs or trips to the hay ring, so there can be false positives.

There can, also, be ways to use the animals in the herd or buy a special animal to do the job. One special employee on an operation which uses extensive AI may be a gomer or teaser bull. These animals are surgically altered so that their penis actually comes out of the side of their body. They, also, may or may not be vasectomized. Bulls may be fitted with chin ball markers as an added feature so that females which are mounted will also be marked. They still have the libido of a bull, but not necessarily the ability to service a cow. They do have drawbacks. There is the expense of having the animal surgically altered, and some altered bulls find ways to get cows in positions where they can in fact breed them. Also, as they are intact, they still act like bulls.

In more recent years, there have been several patches which have become available. The product that has been on the market the longest is called a Kamar® Heat Mount® detector. These devices are a patch designed to be glued to the female’s tailhead. When not activated, they are white in color. But, when an animal fixed with one is mounted, the weight of the animal riding her will cause a capsule full of ink inside the patch to break and it will turn red. These patches are highly visible, which is valuable during heat observation. Kamars® are now available in a peel and stick version, also, so that back tag glue is not necessary.

A similar product available is called a Bovine Beacon. Like the Kamar®, they are a patch glued to the animal, which, also, has a capsule that changes color when popped. In this case, the device actually glows and will glow for 24 hours after the pressure is applied. Another feature of the Bovine Beacon is that it is covered with a bitter coating which discourages cows from trying to lick the device off of their rump. The capsule in these devices is much easier to break than in the Kamar®, so there have been reports of false positives using this technology.

Taking this type of technology a step further, one of the newer products on the market is called the Estrotect™ Heat Detector. It is a flat peel-and-stick design, which is easy to apply and causes less irritation to the cows. They are grey in color when applied and employ a scratch-off-type technology to reveal a bright color underneath. They are available in pink, green and red. Personnel need to use care when using the Estrotect™ as well. Tree branches, hay rings, and fences can cause some of the grey on the sticker to get removed. Also, make sure the cow’s hair is dry when you apply this patch so that it will stay on as long as you need it to. Included with the patches is a cloth, which will help remove dirt and stray hairs. When a female is truly in heat, the patch will have no trace of grey.

There are, also, electronic means of heat detection, which are now available to producers. The Heat Watch system consists of monitors mounted on the rumps of females in mesh pouches. These units have a button-triggered transmitter, which records standing-heat activity. The system default for standing estrus is at least three mounts of two seconds or more each, occurring within a four-hour period. The time of the first mount in the four-hour period is logged as the start of standing heat. It has the ability to record every mount that an animal stands for, often generating extensive amounts of data for each female. This system has its own software so that all information may be accessed on a computer when it is needed. These devices are quite pricey, but depending on the operation and the amount of artificial insemination performed, the price may be justified. It is a valuable tool in large embryo transfer programs.

There are, also, several devices which are all-inclusive and mounted on the cow. The Tattle Tale is an all-inclusive device which has a 12-hour timer on it. Once a female stands for a three-second mount, the timer begins. It has a series of 12 lights which correspond to each hour of time. Therefore, it is easy to determine how long a female has been in heat. They can be reused several times, and the batteries can be replaced, so they can be somewhat more economical. Its data cannot be downloaded onto a computer; it is somewhat like a freestanding computer. The Mount Count is very similar to the Tattle Tale, being all inclusive in a plastic case which is mounted to the cow. In this case, this device has a light signaling suspect heat after the female has been mounted for three seconds, a light indicating standing heat when she has been mounted at least three times in four hours, and a light indicating optimal breeding time which will be on from four to 14 hours after the onset of heat. The Bulls Eye system has inclusive monitors mounted on each animal, but it has the added feature of a handheld read out, which can be used from up to 100 feet away to obtain animal information.

There are a variety of ways that heat can be detected, and no one knows their animals better than an observant producer. AI is a powerful tool which can be a tremendous asset to an operation. Making the time and effort to employ proper heat detection will make huge difference in the success of a breeding program.