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Friday, May 18, 2018

Heat Detection for Successful A.I. Program


Heat (estrus) is simply the period of time when a cow or heifer is sexually receptive and signals that an egg, ready to be fertilized, is about to be released. It normally occurs every 18 to 24 days. In a natural breeding program, the bull is the one that determines when a cow is in heat. In an AI program, you make the decisions.
Heat detection is just another step in the more intensive management system that is part of artificial insemination. It is not difficult, but it does demand both time and attention. If you want your AI program to be successful, you cannot cut corners here.
You have to learn what the bull knows instinctively, but once you have that knowledge, you can easily get the equipment needed for detection eyesight, a pencil and a notebook. Your cows must be identified, too. Ear tags, neck chains or number brands will work, just as long as they are easy to read and can be read from a distance.
Essentially, successful heat detection begins with understanding one simple fact: there is only one sure sign of heat -- a cow stands while other animals mount her. This is appropriately termed standing heat.
Your Responsibility
During the time you are detecting, neither you nor the cows should be distracted in any way. Heat detection periods should not be scheduled to coincide with feeding. Success requires absolute, and total attention. Because cows' responses can be modified by disease, hunger, thirst, fatigue, or fear, it is up to you to make sure the cows are healthy and content and in a familiar environment. They should be given time to get used to the breeding pasture before the breeding season. The cows should be familiar with you and not afraid of your presence. When you detect, it is important to move through the herd quietly. Adequate facilities vary from operation to operation. The area for detection should be large enough to allow the cows to mingle freely, but small enough so that all of them can be watched at once.   
Of course cows have to be cycling, which means they must be healthy and have been receiving a good level of nutrition. Age and weight determine when heifers first cycle, but 13 to 14 months of age is a good rule of thumb. Cows need about 60 days after calving before rebreeding; first calf heifers may require a longer period of time, particularly if the nutrition program is less than optimal.
Be aware that weather changes and temperature extremes can cause cows to exhibit estrus differently (or less noticeably). You can't do much about either of those factors, but you should watch even more carefully at those times.
The Routine
You will need to spend at least 20-30 minutes, twice a day, every day, heat detecting. Ideally, you will heat detect first thing in the morning and then again late in the evening. Both research and practical experience indicate this pattern of visual heat detection is well worth the time invested.
Data collected at the Meat Animal Research Center in Nebraska show that 58 percent of the cows in heat were spotted with one morning observation. Only 28 percent were found if the daily check was at noon; 49 percent were detected by checking only in the evening. With two checks, one first thing in the morning and the other late in the evening, 94 percent were detected.
A Cornell University study yielded similar patterns: from 6 a.m. to noon, 22 percent of the cows showed heat; from noon to 6 p.m., 10 percent did; from 6 p.m. to midnight, 25 percent; and from midnight to 6 a.m., 43 percent.
Accuracy of detection increases with frequency of observation, but the twice-a-day routine is practical and produces acceptable results.
All of this essentially means that timing is of great importance in a successful AI program. The average time a female is in standing heat is about 4 to 12 hours; cows usually ovulate 25 to 30 hours after first standing. The life of an egg, once released, is six to 10 hours.
On the other side of the fertilization equation, sperm cells have to be in the reproductive tract for about five to six hours before they are capable of fertilization. And the sperm is viable for 24 hours.  So, in an ideal world, insemination should take place six to eight hours before ovulation.
Traditionally, cows and heifers are inseminated about 12 hours after they are first observed standing. Those standing in the morning are bred that night; those standing in the evening are held over and then inseminated first thing the next morning. It works well with the twice-a-day routine established for detection.
Secondary Heat Signs
When you are detecting for estrus, remember the primary sign is standing heat. There are, however, secondary signs you should know and note. The following signs usually indicate that a cow is in actual standing heat or that she’s less then 12 hours from coming into heat.
A cow coming into heat may mount other cows, and she may urinate frequently. She may also lay her head over the backs of her herdmates.  Nervousness, walking the fence, bawling, spooking, butting other cows and standing while others are lying down are other possible signs. In addition, a cow coming into heat can be off her feed. She may not let her milk down, and her calf may be protesting. The lips of her vulva can also be red and slightly swollen; she may have watery mucous hanging in strings from her vulva. She may pass a lot of mucous, which is most obvious when she is mounting another cow.
Cows in heat, or about to come into heat, tend to congregate. Because mounting activity increases when more than one cow is in heat, it is not a bad idea to keep a cow in the herd that is standing until it's time for her to be inseminated. If you do that, keep in mind that footing must be good.
When a cow is in heat, she's likely to have mud on her rump and sides, courtesy of the cows that have been riding her. For the same reason, the hair on her tail-head can be rough and matted (this will be most noticeable after heat - too late to be effective). Often you will have bull calves in the herd attempting to mount her as well.
After heat, her vaginal mucous will be thick and rubbery; one to three days after heat, you may notice a bloody discharge.  This is no indication that she is or is not pregnant; it only means she's been in heat. If you failed to observe heat and see a bloody discharge, write down the cow's number and the date in your notebook so you can pay special attention to her in about 15 days.
Remember that the cow that rides may or may not be in heat and that the secondary signs vary so much in length and intensity that they are not reliable in determining when an animal should be inseminated. They are helpful, though. Once you've observed any of these secondary heat signs, make it easy on yourself by using your pencil and notebook to record them. Don't trust your memory, write it down.
By the way, records also help in heat detection. Accurate information compiled and written on heat expectancy charts helps you anticipate when cows are most likely to come into heat.
Once you have done your detecting, the cows you have determined to be in heat can be quietly moved from the herd to the holding area near the breeding facilities.

Much of the information in this article is based on the Artificial Insemination Handbook, available in English, Spanish and Portuguese versions and is produced and distributed by the National Association of Animal Breeders. To order a copy of the handbook, contact NAAB at 573-445-4406.